Morphology-dependent pH-responsive release of hydrophilic payloads using biodegradable nanocarriers

The development of functional nanocarriers with stimuli-responsive properties has advanced tremendously to serve biomedical applications such as drug delivery and regenerative medicine. However, the development of biodegradable nanocarriers that can be loaded with hydrophilic compounds and ensure its controlled release in response to changes in the surrounding environment still remains very challenging. Herein, we achieved such demands via the preparation of aqueous core nanocapsules using a base-catalyzed interfacial reaction employing a diisocyanate monomer and functional monomers/polymers containing thiol and hydroxyl functionalities at the droplet interface. pH-responsive poly(thiourethane–urethane) nanocarriers with ester linkages were synthesized by incorporating polycaprolactone diol, which is susceptible to hydrolytic degradation via ester linkages, as a functional monomer in the reaction formulation. We could demonstrate that by systematically varying the number of biodegradable segments, the morphology of the nanocarriers can be tuned without imparting the efficient encapsulation of hydrophilic payload (>85% encapsulation efficiency) and its transfer from organic to aqueous phase. The developed nanocarriers allow for a fast release of hydrophilic payload that depends on pH, the number of biodegradable segments and nanocarrier morphology. Succinctly put, this study provides important information to develop pH-responsive nanocarriers with tunable morphology, using interfacial reactions in the inverse miniemulsion process, by controlling the number of degradable segments to adjust the release profile depending on the type of application envisaged.

The morphology and release properties of aqueous core nanocapsules for the pH-responsive release of hydrophilic payload was investigated by systematically varying the number of biodegradable segments.     

The influence of nanocarrier architectures on antitumor efficacy of docetaxel nanoparticles

To study the structural influence, hybrid amphiphilic copolymer (G2C₁₈) and linear amphiphilic copolymer (PEG₄₅C₁₈) were utilized to prepare docetaxel (DTX)-loaded nanoparticles through an antisolvent precipitation method. The different architectures of the hydrophilic portion affected the particle sizes significantly, and then induced the different antitumor activity. Compared with DTX/PEG₄₅C₁₈ nanoparticles, the antitumor efficacy of DTX/G2C₁₈ nanoparticles was significantly enhanced, the IC₅₀ value was 2.1-fold lower in vitro, and the inhibition rate was 1.3-fold higher in vivo. These results suggested that the antitumor activity was significantly affected by the architecture of the nanocarriers, and should be considered when nanocarriers are designed.

Nanocarrier branched structure affects the particle size of drug-loaded nanoparticles and further induces different antitumor efficacy.     

Exploring the Contribution of Candidate Genes to Artemisinin Resistance in Plasmodium falciparum

The reduced in vivo sensitivity of Plasmodium falciparum has recently been confirmed in western Cambodia. Identifying molecular markers for artemisinin resistance is essential for monitoring the spread of the resistant phenotype and identifying the mechanisms of resistance. Four candidate genes, including the P. falciparum mdr1 (pfmdr1) gene, the P. falciparum ATPase6 (pfATPase6) gene, the 6-kb mitochondrial genome, and ubp-1, encoding a deubiquitinating enzyme, of artemisinin-resistant P. falciparum strains from western Cambodia were examined and compared to those of sensitive strains from northwestern Thailand, where the artemisinins are still very effective. The artemisinin-resistant phenotype did not correlate with pfmdr1 amplification or mutations (full-length sequencing), mutations in pfATPase6 (full-length sequencing) or the 6-kb mitochondrial genome (full-length sequencing), or ubp-1 mutations at positions 739 and 770. The P. falciparum CRT K76T mutation was present in all isolates from both study sites. The pfmdr1 copy numbers in western Cambodia were significantly lower in parasite samples obtained in 2007 than in those obtained in 2005, coinciding with a local change in drug policy replacing artesunate-mefloquine with dihydroartemisinin-piperaquine. Artemisinin resistance in western Cambodia is not linked to candidate genes, as was suggested by earlier studies.Antimalarial drug resistance is the single most important threat to global malaria control. Over the past 40 years, as first-line treatments (chloroquine and sulfadoxine-pyrimethamine) failed, the malaria-attributable mortality rate rose, contributing to a resurgence of malaria in tropical countries (11). In the last decade, artemisinins, deployed as artemisinin combination therapies (ACTs), have become the cornerstone of the treatment of uncomplicated falciparum malaria (20) and, in conjunction with other control measures, have contributed to a remarkable decrease in malaria morbidity and mortality in many African and Asian countries (4). The recent confirmation of the reduced artemisinin sensitivity of Plasmodium falciparum parasites in western Cambodia has therefore alarmed the malaria community (6). A large containment effort has been launched by the World Health Organization, in collaboration with the national malaria control programs of Cambodia and neighboring Thailand. The resistant phenotype has not been well characterized and is not well reflected by the results of conventional in vitro drug susceptibility assays. No molecular marker has been identified, which impedes surveillance studies to monitor the spread of the resistant phenotype. Identification of molecular markers would give insight into the mechanisms underlying artemisinin resistance and the mechanism of antimalarial action of the artemisinins.Mutations in several candidate genes have been postulated to confer artemisinin resistance. (i) P. falciparum mdr1 (pfmdr1) encodes the P-glycoprotein homologue 1 (Pgh1), which belongs to the ATP-binding cassette transporter superfamily, members of which couple ATP hydrolysis to the translocation of a diverse range of drugs and other solutes across the food vacuole and plasma membranes of the parasite (Fig. ​(Fig.1)1) (5). The gene is located on chromosome 7, is 4.2 kb in length, and contains only one exon. Mutations in and, more importantly, amplification of the wild-type gene confer resistance to the 4-methanolquinoline mefloquine, presumably through an increased ability to efflux the drug (15, 16). Mutations and amplification of the gene have also been associated with reduced in vitro susceptibility to the artemisinins (7, 16). In vivo selection of the pfmdr1 86N allele after artemether-lumefantrine treatment has been observed in Africa (17).Open in a separate windowFIG. 1.Predicted structure and representative haplotypes of P. falciparum multidrug resistance transporter. PfMDR1 is predicted to have 12 transmembrane domains, with its N and C termini located on the cytoplasmic side of the digestive vacuole membrane (adapted from reference 19). Mutations identified in pfmdr1 full-length sequences from Pailin and WangPha are indicated by the red circles. aa, amino acid.(ii) P. falciparum ATPase6 (pfATPase6) encodes the calcium-dependent sarcoplasmic/endoplasmic reticulum calcium ATPase, which was shown to be a target for the artemisinin drugs in Xenopus oocytes (8). The gene is 4.3 kb in length and has three exons on chromosome 1. A single amino acid change in pfATPase6, L263E, is associated with resistance to artemisinins in this model (8, 18). Mutation S769N in pfATPase6 in P. falciparum isolates from French Guiana was associated with decreased in vitro sensitivity to artemether (10). However, it is unclear whether mutations in pfATPase6 are associated with artemisinin resistance in vivo (1).(iii) The electron transport chain in the mitochondrial inner membrane is key to the malaria parasite''s capacity to produce ATP. Since activation of the endoperoxide bridge in the artemisinins by an electron donor is central to their antimalarial activity, mitochondrial proteins are potential activation sites for the artemisinins. Mutations in the mitochondrial genome, which is 6 kb long and which contains three genes (cytochrome b, COXI, COXIII), could therefore potentially change susceptibility to the artemisinins.(iv) ubp-1, a 3.3-kb gene located on chromosome 2, encodes a deubiquitinating enzyme. Mutations V739F and V770F in ubp-1 of P. chabaudi were recently identified by linkage group analysis of an elegant genetic-cross experiment to confer resistance to artesunate in this rodent malaria parasite (9).(v) Laboratory-induced artemisinin resistance in the P. chabaudi model has been demonstrated in a chloroquine-resistant strain. This suggests that chloroquine resistance in this model might be a prerequisite for the subsequent development of artemisinin resistance. We therefore also assessed the parasite genome for the presence of the P. falciparum CRT (pfCRT) K76T mutation, which plays a central role in the chloroquine resistance of P. falciparum.We report here the molecular characteristics of these five groups of genes in P. falciparum isolates from western Cambodia, where most infections show reduced sensitivity to artesunate, compared to those of strains obtained from northwestern Thailand, where infections are artemisinin sensitive (6).     

Stearylamine Liposomal Delivery of Monensin in Combination with Free Artemisinin Eliminates Blood Stages of Plasmodium falciparum in Culture and P. berghei Infection in Murine Malaria

The global emergence of drug resistance in malaria is impeding the therapeutic efficacy of existing antimalarial drugs. Therefore, there is a critical need to develop an efficient drug delivery system to circumvent drug resistance. The anticoccidial drug monensin, a carboxylic ionophore, has been shown to have antimalarial properties. Here, we developed a liposome-based drug delivery of monensin and evaluated its antimalarial activity in lipid formulations of soya phosphatidylcholine (SPC) cholesterol (Chol) containing either stearylamine (SA) or phosphatidic acid (PA) and different densities of distearoyl phosphatidylethanolamine-methoxy-polyethylene glycol 2000 (DSPE-mPEG-2000). These formulations were found to be more effective than a comparable dose of free monensin in Plasmodium falciparum (3D7) cultures and established mice models of Plasmodium berghei strains NK65 and ANKA. Parasite killing was determined by a radiolabeled [³H]hypoxanthine incorporation assay (in vitro) and microscopic counting of Giemsa-stained infected erythrocytes (in vivo). The enhancement of antimalarial activity was dependent on the liposomal lipid composition and preferential uptake by infected red blood cells (RBCs). The antiplasmodial activity of monensin in SA liposome (50% inhibitory concentration [IC₅₀], 0.74 nM) and SPC:Chol-liposome with 5 mol% DSPE-mPEG 2000 (IC₅₀, 0.39 nM) was superior to that of free monensin (IC₅₀, 3.17 nM), without causing hemolysis of erythrocytes. Liposomes exhibited a spherical shape, with sizes ranging from 90 to 120 nm, as measured by dynamic light scattering and high-resolution electron microscopy. Monensin in long-circulating liposomes of stearylamine with 5 mol% DSPE-mPEG 2000 in combination with free artemisinin resulted in enhanced killing of parasites, prevented parasite recrudescence, and improved survival. This is the first report to demonstrate that monensin in PEGylated stearylamine (SA) liposome has therapeutic potential against malaria infections.     

Nucleoside-lipid-based nanocarriers for methylene blue delivery: potential application as anti-malarial drug

Nucleolipid supramolecular assemblies are promising Drug Delivery Systems (DDS), particularly for nucleic acids. Studies based on negatively and positively charged nucleolipids (diC16dT and DOTAU, respectively) demonstrated appropriate stability, safety, and purity profile to be used as DDS. Methylene Blue (MB) remains a good antimalarial drug candidate, and could be considered for the treatment of uncomplicated or severe malaria. However, the development of MB as an antimalarial drug has been hampered by a high dose regimen required to obtain a proper effect, and a short plasmatic half life. We demonstrated that nanoparticles formed by nucleolipid encapsulation of MB using diC16dT and DOTAU (MB-NPs) is an interesting approach to improve drug stability and delivery. MB-NPs displayed sizes, PDI, zeta values, and colloidal stability allowing a possible use in intravenous formulations. Nanoparticles partially protected MB from oxido-reduction reactions, thus preventing early degradation during storage, and allowing prolongated pharmacokinetic in plasma. MB-NPs'' efficacy, tested in vitro on sensitive or multidrug resistant strains of Plasmodium falciparum, was statistically similar to MB alone, with a slightly lower IC₅₀. This nucleolipid-based approach to protect drugs against degradation represents a new alternative tool to be considered for malaria treatment.

Nucleolipids protects methylene blue against reduction (induced by light and chemical reductants) and do not impair antimalarial activity.     

Chloroquine Remains Effective for Treating Plasmodium vivax Malaria in Pursat Province,Western Cambodia

Chloroquine (CQ) is used to treat Plasmodium vivax malaria in areas where CQ resistance has not been reported. The use of artemisinin (ART)-based combination therapies (ACTs) to treat CQ-sensitive P. vivax infections is effective and convenient but may promote the emergence and worsening of ART resistance in sympatric Plasmodium falciparum populations. Here, we show that CQ effectively treats P. vivax malaria in Pursat Province, western Cambodia, where ART-resistant P. falciparum is highly prevalent and spreading. (This study has been registered at ClinicalTrials.gov under registration no. {"type":"clinical-trial","attrs":{"text":"NCT00663546","term_id":"NCT00663546"}}NCT00663546.)     

Synthesis,supramolecular organization and thermotropic phase behaviour of N-acyltris(hydroxymethyl)aminomethane

Herein, we reported the supramolecular organization of N-acyltris(hydroxymethyl)aminomethane (NATM) in the solid state as well as in aqueous solution. Single crystal X-ray diffraction revealed that NATM adopts a fully interdigitized structure. The thermodynamic parameters associated with thermotropic phase behaviour of NATM was determined by differential scanning calorimetry. The molecular packing and phase state of the NATM analyzed by laurdan and prodan fluorescence supports the formation of an interdigitized phase in aqueous solution. The potential application of the self-assembled NATM vesicles was demonstrated through entrapping model drug, Rhodamine B.

Self assembly of N-acyltris(hydroxymethyl)aminomethane into interdigitized vesicles.     

Co-delivery of paclitaxel and gemcitabine via a self-assembling nanoparticle for targeted treatment of breast cancer

Multi-functional nanoparticles can be used to improve the treatment index and reduce side effects of anti-tumor drugs. Herein, we developed a kind of multi-functional and highly biocompatible nanoparticle (NP) loaded with folic acid (FA), paclitaxel (PTX) and gemcitabine (GEM) via self-assembly to target cancer cells. The transmission electron microscopy (TEM) results showed that multi-functional FA targeting nanoparticles (MF-FA NPs) exhibited spherical morphology and favorable structural stability in aqueous solution. In addition, NPs (MF-FA NPs and MF NPs) exhibited comparable proliferation inhibition to breast cancer cell 4T1 compared with the pure drug. In in vivo antitumor studies, NPs showed an obviously enhanced anti-tumor efficacy compared with the pure drug. Furthermore, MF-FA NPs displayed higher tumor growth inhibition than MF NPs due to the specific targeting of FA to cancer cells. Consequently, the novel MF-FA NPs could be used as a potential chemotherapeutic formulation for breast cancer therapy.

Preparation of MF-FA nanoparticles and the release behavior of drugs in tumor cells.     

Characterization of the global metabolic profile of liquiritin in rat plasma,urine, bile and feces based on UHPLC-FT-ICR MS

Liquiritin is a major flavonoid in Radix Glycyrrhizae and it has been reported to possess various pharmacological activities. In the present work, a strategy based on an ultra high performance liquid chromatography combined with Fourier transform ion cyclotron resonance mass spectrometry (UHPLC-FT-ICR MS) method was proposed to systematically characterize the in vivo metabolites of liquiritin for the first time. After oral administration of liquiritin to rats in a single dose of 120 mg kg⁻¹, the rat plasma, urine, feces and bile samples were collected and used to discover metabolites. As a result, besides the parent drug, a total of 76 metabolites (6 phase I and 70 phase II metabolites) of liquiritin were detected and tentatively identified. It was indicated that the metabolic pathways of liquiritin in rats included oxidation, reduction, deglycosylation, isomerization, methylation, glucuronidation and sulfation. In summary, the results could provide valuable information regarding the metabolism of liquiritin in rats, which could contribute to a better understanding of its action mechanism.

Liquiritin is a major flavonoid in Radix Glycyrrhizae and it has been reported to possess various pharmacological activities.     

Layered double hydroxide-based nanocomposite scaffolds in tissue engineering applications

Layered double hydroxides (LDHs), when incorporated into biomaterials, provide a tunable composition, controllable particle size, anion exchange capacity, pH-sensitive solubility, high-drug loading efficiency, efficient gene and drug delivery, controlled release and effective intracellular uptake, natural biodegradability in an acidic medium, and negligible toxicity. In this review, we study potential applications of LDH-based nanocomposite scaffolds for tissue engineering. We address how LDHs provide new solutions for nanostructure stability and enhance in vivo studies'' success.

In this review, we study potential applications of LDHs for tissue engineering and discuss some recent studies on biocompatibility, antibacterial and osteogenic differentiation behaviors of LDHs.     

Can repurposing drugs play a role in malaria control?

Innovative drug treatments for malaria, optimally with novel targets, are needed to combat the threat of parasite drug resistance. As drug development efforts continue, there may be a role for a host-targeting, repurposed cancer drug administered together with an artemisinin combination therapy that was shown to improve the speed of recovery from a malaria infection.

Reduction in the global burden of malaria has stalled over the past several years. In 2019, there were ∼229 million cases in 87 malaria-endemic countries, resulting in an estimated 386,000 fatalities (WHO, 2020). The impact of the ongoing COVID-19 pandemic on malaria control has yet to be determined; however, there is great concern that the diversion of funds, interventions, and supplies will only lead to increased malaria morbidity and mortality (Weiss et al., 2021). Emerging and widespread parasite drug resistance has already complicated malaria control. Resistance to the components of artemisinin combination therapies (ACTs), the worldwide standard treatment for Plasmodium falciparum malaria, is a serious concern in Southeast Asia, and the inevitable loss of efficacy of these treatments in Africa must be delayed for as long as possible.A persistently high burden of disease demands a rethinking of malaria control, including the development of new drug combinations to treat malaria. A potential novel approach to treatment was recently described by Chien et al. (2021). They demonstrated that targeting a host protein with a repurposed cancer drug may serve as an adjunctive treatment to the standard of care, in this case dihydroartemisinin/piperaquine for uncomplicated P. falciparum malaria infection. In a small study performed in Vietnam, they found that the addition of the tyrosine kinase inhibitor (TKI) imatinib to the standard of care led to faster resolution of fevers and parasitemia with no additional adverse events. These results are especially intriguing given the nature of artemisinin resistance, in which, following treatment, parasites remain in the infected host for an extended period of time (WHO, 2020).Artemisinin and its derivatives are highly potent antimalarial drugs notable for their fast killing of multiple parasite stages. In general, the use of artemisinin is associated with rapid resolution of clinical symptoms and clearance of parasitemia in uncomplicated malaria and decreased mortality in severe disease. For this reason, reports of treatment failures with ACTs in western Cambodia starting over a decade ago alarmed the global health community. Decreased efficacy of artemisinin, likely from earlier extensive use as monotherapy, led to the emergence of resistance to partner drugs. In many areas of the Greater Mekong Subregion (GMS), piperaquine failures are now common, such that guidelines have changed and lumefantrine has increasingly become the partner drug of choice (Hamilton et al., 2019). Resistance to the artemisinin component of ACTs is defined clinically as a delayed parasite clearance time, meaning parasites are still observable after 72 h in peripheral blood by microscopy (WHO, 2020). Currently, >80% of infections in the GMS are noted to have a prolonged parasite clearance half-life and are strongly association with polymorphisms in the parasite protein P. falciparum Kelch 13 (Pfkelch13; WHO, 2020; Rosenthal, 2021). The dominant GMS Pfkelch13 polymorphism, C580Y, has also emerged independently in Guyana and Papua New Guinea, though with unclear clinical relevance (Mathieu et al., 2020; Miotto et al., 2020). Recent studies from Africa, in particular Rwanda and Uganda, are of great concern, as emergence and expansion of PfKelch13 mutations associated with both in vitro and in vivo resistance was recently reported (Balikagala et al., 2021; Miotto et al., 2020; Rosenthal, 2021). Emergence of clinically relevant artemisinin resistance in Africa and the subsequent inevitable partner drug failure in areas with the heaviest burden of disease would be catastrophic for malaria control (Rosenthal, 2021).The optimal response to growing ACT failure is hotly debated. To date, there are a limited number of antimalarial agents available with an even fewer number of molecular targets, which makes the idea of a host target so intriguing (Fig. 1). Novel antimalarials, some with new targets, are in the development pipeline but are unlikely to be available within the next 5 yr and are often susceptible to rapidly arising drug resistance. Increasing the duration of ACT usage from 3 to 5 d appears to be effective, but anticipated poor compliance to the extended therapy may exacerbate resistance. Recent studies assessed the potency and safety of triple ACTs (TACT), combining an ACT with a second partner drug, typically mefloquine or amodiaquine, both of which target the food vacuole but have their own well-documented resistance liabilities (van der Pluijm et al., 2020). Thus, there is great potential benefit for a repurposed, affordable antimalarial with a mechanism independent of the other ACT components as part of a TACT regimen, especially if such a novel agent could forestall the further development and spread of artemisinin resistance.Open in a separate windowFigure 1.Current antimalarial drugs and putative targets. Many antimalarials such as quinolines have well-defined targets, including the food vacuole where they interfere with hemoglobin digestion or the cyclins that target the parasite apicoplast. The artemisinins cause widespread cellular damage once activated inside the parasite. Imatinib targets a human tyrosine kinase in the host cell that phosphorylates the RBC membrane protein Band 3 as the cell ages and during parasite maturation. When phosphorylation of Band 3 is inhibited by imatinib, Band 3 fails to cluster and the RBC membrane remains resistant to parasite rupture, entrapping the daughter merozoites that would normally infect new RBCs.Repurposing existing drugs has been proposed as an approach to hasten the identification and study of novel therapeutics. However, the reality of the impact of repurposed drugs has been limited to date, and there are potentially many pitfalls while proposing new uses for old drugs (Pessanha de Carvalho et al., 2021; Begley et al., 2021). Antibiotics that target the specialized parasite organelle of prokaryotic origin, the apicoplast, have been repurposed to be part of second-line malaria treatment options (Biddau and Sheiner, 2019; Pessanha de Carvalho et al., 2021) and chemoprevention but continue to play an important role in malaria control (Fig. 1). The greatest success in drug repurposing for an infectious disease is not pathogen targeting, but host immune response directed. Thalidomide is used to treat a particular complication of leprosy marked by an overactive immune response, termed erythema nodosum leprosum (Begley et al., 2021).Targeting a host protein would be a unique mechanism of action for an antimalarial drug. Work to define the mechanism of action of host TKI against P. falciparum was extensively explored in the laboratory before testing efficacy in the field. The first TKI approved by the Food and Drug Administration for management of chronic myelogenous leukemia (CML), imatinib, was shown to have activity against P. falciparum in vitro (Kesely et al., 2020). TKIs remain the first-line therapy for chronic phase CML with the exception of pregnant women (Hochhaus et al., 2017). Thus, there is widespread experience with these agents, and in general, patients tolerate TKIs for long-term treatment with well-described side effect profiles. Side effects during short-term treatment for falciparum malaria are likely to be minimal but remain to be studied outside an exclusively adult male population (Chien et al., 2021).Laboratory-based studies revealed that malaria parasites are unable to egress from their host RBC when cultures are treated with TKIs (Pantaleo et al., 2017). Treatment with imatinib and other TKIs block changes to the host RBC membrane that occur during parasite development, in particular changes to a protein called Band 3, an abundant integral RBC membrane protein that has multiple functions including membrane stabilization. As the RBC ages, Band 3 forms clusters that destabilize the membrane; this process is accelerated under conditions of oxidative damage and during malaria parasite development (Pantaleo et al., 2017; Shimo et al., 2015). Band 3 phosphorylation is required for clustering but is blocked when a host tyrosine kinase (SYK; spleen tyrosine kinase) is inhibited by imatinib (Fig. 1). Previous work has shown that by preventing the phosphorylation of Band 3, the membrane destabilization needed for the mature parasite to egress from the RBC and continue the erythrocytic cycle of infection is blocked. The parasites remain viable but stuck within in the host cell, theoretically prolonging parasite exposure to their own toxic metabolites (Kesely et al., 2020; Pantaleo et al., 2017). When tested in combination, imatinib was shown to be synergistic with artemisinin in vitro (Tsamesidis et al., 2020). In the clinical trial reported by Chien et al. (2021), the faster reduction in parasitemia observed in the dihydroartemisinin/piperaquine plus imatinib arm is potentially meaningful in an area where prolonged clearance time is a harbinger of ACT failure. Though they found only one patient infected with a parasite bearing a PfKelch13 mutation, other parasite factors can lead to prolonged parasite clearance and predate the full emergence of PfKelch13-mediated treatment failure. Parasite resistance to TKIs, on the other hand, are at least theoretically unlikely to emerge, as P. falciparum lack their own tyrosine kinases that could serve as an imatinib target.While this novel therapeutic approach coupled more rapid parasite clearance and faster reduction of fever, many questions must be addressed before imatinib should be considered for more widespread use in combination with ACTs. Of particular importance is whether the faster parasite clearance or reduction in fever would persist with different ACT dosing and currently recommended regimens using lumefantrine, amodiaquine, or pyronaridine as the partner drug, for example. Safety data from use in CML are well established, yet additional safety data for malaria treatment are needed from larger trials, especially in women and children, the two groups most heavily affected by malaria. Women who have clinical immunity to malaria are known to be at risk of more severe disease during pregnancy-associated malaria. For this reason, intermittent preventative treatment with various antimalarials during pregnancy is known to improve outcomes for both mother and child (Kakuru et al., 2020). Imatinib is associated with increased fetal abnormalities and miscarriage and is not recommended for pregnant or nursing women. Inability to use this agent in women of childbearing age is an important limitation to consider. Similarly, safety in children needs to be considered, as the majority of malaria deaths occur in children under 5 yr of age. Finally, in Africa, where the malaria burden is the highest, host immunity often plays a critical role in parasite clearance, and ACTs generally remain highly effective in the region (Djimdé et al., 2003). The benefit of imatinib toward parasite clearance in these populations with varying degrees of immunity needs to be studied.Malaria is currently a treatable disease, and we must be creative and diligent to assure the availability of new, efficacious therapies. Novel approaches are needed as the threat of drug resistance grows. Imatinib has the advantage of being a novel affordable agent that has a unique mechanism of action. Importantly, as its target is host derived, it should be less likely to fail due to the development of parasite resistance. Malaria researchers will need to study and consider how to use agents such as imatinib that are not treatments on their own but may enhance the action of current therapy to forestall the emergence and potential spread of additional drug resistant malaria, in a safe and cost-effective manner. The encouraging findings from the field warrant further studies on imatinib and other host-targeting approaches for malaria.     

Piperaquine Pharmacodynamics and Parasite Viability in a Murine Malaria Model

Piperaquine (PQ) is an important partner drug in antimalarial combination treatments, but the long half-life of PQ raises concerns about drug resistance. Our aim was to investigate the extended antimalarial effect of PQ in a study of drug efficacy, reinoculation outcomes, and parasite viability after the administration of a single dose of PQ in the murine malaria model. Initially, male Swiss mice were inoculated with Plasmodium berghei and at 64 h after parasite inoculation were given PQ phosphate at 90 mg/kg of body weight intraperitoneally. Parasite viability, drug efficacy, reinoculation responses, and parasite resistance were determined at 25, 40, 60, 90, and 130 days after drug administration. At each time point, six mice were reinoculated with 10⁷ P. berghei parasites and blood was harvested from another four mice for viability passage into naïve mice (n = 5 for each blood sample) and from another two mice for determination of the plasma PQ concentration. The efficacy study demonstrated that the residual PQ concentrations did not suppress the infection after 25 days. Viable parasites were present up to 90 days after PQ dosing, although only 50% and 25% of the passaged parasites remained viable at 60 and 90 days postdosing, respectively. Viable parasites passaged into the naïve hosts were generally resistant to PQ when they were exposed to the drug for a second time. PQ was found to have a substantial antimalarial effect in this model, and the effect appears to be sufficient for a host immunological response to be established, resulting in the long-term survival of P. berghei-infected mice.Piperaquine (PQ) is a bisquinoline antimalarial drug used in contemporary artemisinin combination treatment (ACT) strategies as a partner to dihydroartemisinin (1, 4). In order to prevent drug resistance and early parasite recrudescence associated with the short-acting artemisinin drugs, ACT partner drugs should be long-acting schizonticides with half-lives (t_1/2s) exceeding 4 days, or two asexual parasite life cycles (10, 21). Recent pharmacokinetic studies have demonstrated that PQ has biphasic elimination and a long terminal t_1/2 of 12 to 28 days in humans (10, 15, 31, 32).Several clinical trials of the PQ-dihydroartemisinin combination have shown that it has a high degree of efficacy and good tolerability for the treatment of Plasmodium falciparum infections (1, 2, 5, 7, 11, 12, 17). While this combination is now considered the first-line antimalarial treatment in some Southeast Asian countries, the long t_1/2 of PQ raises concerns about adverse effects and drug resistance (6, 10, 20, 22). Detailed preclinical pharmacodynamic data for PQ, alone or in combination with artemisinin drugs, would complement clinical studies, especially when there is interest in the therapeutic impact of persistent, low PQ concentrations.We have recently demonstrated that PQ has a biphasic elimination profile in mice and has a terminal elimination t_1/2 in malaria parasite-infected and healthy mice of 18 days and 16 days, respectively (18). The pharmacodynamic component of our study revealed that after the administration of a single dose of PQ phosphate (10 to 90 mg/kg of body weight) there was a rapid reduction in the level of parasitemia to a subdetectable parasite density in the groups receiving high doses and recrudescence approximately 7 days later. In the group receiving the highest dose (90 mg/kg of body weight), a subclinical infection persisted for at least 60 days, at which time the plasma PQ concentration was estimated to be 20- to 100-fold lower than earlier therapeutic levels. However, reinoculation with P. berghei parasites did not cause the standard lethal infection that was found in control mice, suggesting that the mice treated with PQ had developed a degree of immunity to the parasites (18, 19). The present study was therefore conducted to investigate drug efficacy, reinoculation outcomes, and parasite viability after the administration of a single dose of PQ in the murine malaria model.     

Simple weak-acid derivatives of paclitaxel for remote loading into liposomes and improved therapeutic effects

Liposomes are among the most successful nanocarriers; several products have been marketed, all of which were prepared by active loading methods. However, poorly water-soluble drugs without ionizable groups are usually incorporated into the lipid bi-layer of liposomes by passive loading methods, with serious drug leakage during blood circulation. Furthermore, there have been few improvements in their anti-cancer activity and safety. Herein, we designed and synthesized three weak-acid modified paclitaxel (PTX) derivatives with a one-step reaction for the remote loading of liposomal formulations. By comparison, PTX-succinic acid liposomes (PTX-SA LPs) exhibited the highest encapsulation efficiency (97.2 ± 1.8%) and drug loading (8.84 ± 0.16%); meanwhile, there was almost no change in their particle size or zeta potential within one month. Furthermore, compared with Taxol®, the PTX-SA LPs showed a 4.35-fold prolonged half-time, enhanced tumor accumulation, and an increased maximum tolerated dose (MTD) of more than 30 mg kg⁻¹. As a result, the PTX-SA LPs displayed significantly improved in vivo anti-cancer efficacy in comparison with Taxol®. Therefore, weak-acid modification is proved to be a simple and effective method to achieve remote loading and high encapsulation efficiency of poorly soluble drugs, showing great potential for clinical application.

A remote loading liposomal formulation of weak-acid paclitaxel derivative with high encapsulation efficiency and high drug loading, improved therapeutic efficiency and negligible toxicity.     

Synthesis of non-ionic bolaamphiphiles and study of their self-assembly and transport behaviour for drug delivery applications

A series of four bolaamphiphiles with different hydrophilic units has been synthesised. All the amphiphiles were well characterised from their physiochemical data. The aggregation tendency of newly synthesised amphiphiles was studied using fluorescence spectroscopy, dynamic light scattering (DLS), and cryogenic electron microscopy (cryo-TEM). Furthermore, their application as nanocarriers for hydrophobic guests was demonstrated by using two established standards, i.e. the dye Nile red and the drug nimodipine. A cytotoxicity and cellular uptake study has been carried out using A549 cells. Due to the presence of an ester linkage in PEG based bolaamphiphiles, a drug release study was performed in the presence of an immobilized enzyme Novozym-435 (a lipase).

Non-ionic bolaamphiphiles as nanocarrier for biomedical applications.     

Ex Vivo Drug Susceptibility Testing and Molecular Profiling of Clinical Plasmodium falciparum Isolates from Cambodia from 2008 to 2013 Suggest Emerging Piperaquine Resistance

Cambodia''s first-line artemisinin combination therapy, dihydroartemisinin-piperaquine (DHA-PPQ), is no longer sufficiently curative against multidrug-resistant Plasmodium falciparum malaria at some Thai-Cambodian border regions. We report recent (2008 to 2013) drug resistance trends in 753 isolates from northern, western, and southern Cambodia by surveying for ex vivo drug susceptibility and molecular drug resistance markers to guide the selection of an effective alternative to DHA-PPQ. Over the last 3 study years, PPQ susceptibility declined dramatically (geomean 50% inhibitory concentration [IC₅₀] increased from 12.8 to 29.6 nM), while mefloquine (MQ) sensitivity doubled (67.1 to 26 nM) in northern Cambodia. These changes in drug susceptibility were significantly associated with a decreased prevalence of P. falciparum multidrug resistance 1 gene (Pfmdr1) multiple copy isolates and coincided with the timing of replacing artesunate-mefloquine (AS-MQ) with DHA-PPQ as the first-line therapy. Widespread chloroquine resistance was suggested by all isolates being of the P. falciparum chloroquine resistance transporter gene CVIET haplotype. Nearly all isolates collected from the most recent years had P. falciparum kelch13 mutations, indicative of artemisinin resistance. Ex vivo bioassay measurements of antimalarial activity in plasma indicated 20% of patients recently took antimalarials, and their plasma had activity (median of 49.8 nM DHA equivalents) suggestive of substantial in vivo drug pressure. Overall, our findings suggest DHA-PPQ failures are associated with emerging PPQ resistance in a background of artemisinin resistance. The observed connection between drug policy changes and significant reduction in PPQ susceptibility with mitigation of MQ resistance supports reintroduction of AS-MQ, in conjunction with monitoring of the P. falciparum mdr1 copy number, as a stop-gap measure in areas of DHA-PPQ failure.     

An iRGD peptide conjugated heparin nanocarrier for gastric cancer therapy

The cis-diamminedichloroplatinum(ii) (DDP, cisplatin) is an important antitumor drug for the therapy of gastric cancer in clinics, but it is limited by its nonspecific tissue distribution and severe side effects. Here, an integrin targeted drug delivery system iRGD-heparin nanocarrier (iHP) was successfully synthesized. The iHP has several unique properties. First, this nanocarrier has excellent biodegradation due to its heparin biopolymer frame. Second, it is biocompatible because succinic anhydride-modified heparin has no anticoagulant activity and cell toxicity. We proved that from anticoagulant function evaluation and a cytotoxicity test. Third, iRGD was conjugated to the nanoparticles as an integrin-targeting ligand. Our results showed that iHP has precise targeting to integrin-overexpressed human gastric cancer cells MKN-45P in vitro and tumor tissues in vivo. Hence, we synthesized targeted nanoparticles iHP-DDP (iHDDP) and untargeted nanoparticles HP-DDP (HDDP). In our result, iHDDP showed higher antitumor efficacy than HDDP in vitro and in vivo. And in comparison with free DDP, the iHDDP nanoparticle delivery system showed satisfactory antitumor activity of DDP without weight loss or liver and kidney damage in nude mice bearing MKN-45P tumors.

A nontoxic, low immunogenic and high specific drug delivery system for gastric cancer.     

Photosensitizer-loaded biomimetic platform for multimodal imaging-guided synergistic phototherapy

Photodynamic therapy (PDT) has attracted much attention as a strategy for tumor therapy. However, the insolubility and poor tumor-targeting ability of most photosensitizers (PSs) hinder PDT from further development. Therefore, it is necessary to explore new carriers with good water solubility and biocompatibility to deliver PSs to tumors. Melanin nanoparticles are novel biomimetic nanocarriers with excellent biocompatibility, loading capacity, photothermal therapy (PTT) and magnetic resonance (MR)/photoacoustic (PA) imaging properties. Here we designed polydopamine melanin nanoparticles (PDMNs) as a delivery platform for the photosensitizer Chlorin e6 (PDMN–Ce6) and realized its application as a theranostic agent for tumor therapy. The PDMN–Ce6 exhibited excellent biocompatibility, good water solubility and high loading capability (35.2 wt%) for Ce6. Compared with the free Ce6, PDMN–Ce6 showed higher cellular internalization and superior synergistic phototherapy effects in an in vitro study. An in vivo study indicated that the accumulation of PDMN–Ce6 at tumor sites was 2.8-fold higher than that of free Ce6 at 24 h post-injection, which was beneficial for MR/PA imaging. Moreover, the synergetic therapy significantly inhibited tumor growth, causing tumor necrosis and tumor angiogenesis suppression. These results suggest that our biomimetic and biocompatible platform could improve the delivery of Ce6 to tumors and realize multimodal imaging-guided tumor synergetic phototherapy.

Photodynamic therapy (PDT) has attracted much attention as a strategy for tumor therapy.     

Formulation,characterization and evaluation of morusin loaded niosomes for potentiation of anticancer therapy

Morusin, a water-insoluble prenylated flavonoid is known for its numerous medicinal properties. It manifests its anticancer potential by suppression of genes involved in tumor progression. However, poor solubility of the drug results in low bioavailability and rapid degradation thus hindering its clinical utilization. In order to overcome this, we have synthesized a niosome system composed of non-ionic surfactant span 60 and cholesterol using a thin-layer evaporation technique to improve the aqueous-phase solubility of the drug. Highly cytocompatible niosomes of 479 nm average size with smooth and uniform spherical morphology were synthesized in a facile manner. Unlike free morusin, nanomorusin was found to be freely dispersible in aqueous media. Having an extremely high drug entrapment efficiency (97%), controlled and sustained release of morusin resulting in enhanced therapeutic efficacy was observed in cancer cell lines of 4 different lineages. The results demonstrate that the morusin-niosome system is a promising strategy for enhanced anti-cancer activity against multiple cancer types and could be an indispensable tool for future targeted chemotherapeutic strategies.

Highly cytocompatible morusin-loaded niosomes were synthesized showing high drug loading and encapsulation efficiencies with sustained release of the drug. Enhanced therapeutic efficacy was observed against 4 different cancer cell lines.     

pH-responsive polymeric nanoparticles with tunable sizes for targeted drug delivery

Biodegradable nanoparticles (NPs) have shown great promise as intracellular imaging probes, nanocarriers and drug delivery vehicles. In this study, we designed and prepared amphiphilic cellulose derivatives via Schiff base reactions between 2,3-dialdehyde cellulose (DAC) and amino compounds. Polymeric NPs were facilely fabricated via the self-assembly of the as-synthesized amphiphilic macromolecules. The size distribution of the obtained NPs can be tuned by changing the amount and length of the grafted hydrophobic side-chains. Anticancer drugs (DOX) were encapsulated in the NPs and the drug-loaded NPs based on cellulose derivatives were stable in neutral and alkaline environments for at least a month. They rapidly decomposed with the efficient release of the drug in acidic tumor microenvironments. These drug-loaded NPs have the potential for application in cancer treatment.

Novel nanoparticles for efficient drug delivery were designed and constructed using polymeric 2,3-dialdehyde cellulose (DAC). The drug DOX was encapsulated into nanoparticles and underwent thoroughly controlled release in acidic tumor microenvironments.     

Efficient artificial light-harvesting system constructed from supramolecular polymers with AIE property

Supramolecular luminescent materials in water have attracted much interest due to their excellent tunability, multi-color emission, and environment-friendly behavior. However, hydrophobic chromophores are often affected by poor solubility and aggregation-caused quenching effects in aqueous media. Herein, we report a water-phase artificial light-harvesting system based on an AIE-type supramolecular polymer. Specifically, dispersed nanoparticles in water were prepared from an AIE chromophore-bridged ditopic ureidopyrimidinone (M) based supramolecular polymer with the assistance of surfactants. By co-assembling the hydrophobic chromophores NDI as energy acceptor into the nanocarriers, artificial light-harvesting systems (M–NDI) could be successfully constructed, exhibiting efficient energy transfer and high antenna effects. Furthermore, the spectral emission of the system could be continuously tuned with a relatively small number of acceptors. This work develops an efficient supramolecular light-harvesting system in water, which has potential applications in dynamic luminescent materials.

An artificial light-harvesting system based on supramolecular polymers has been successfully constructed in aqueous media, which displays tunable emission with efficient energy transfer and high antenna effect.