Preparation, characterization, cytotoxicity and transfection efficiency of poly(DL-lactide-co-glycolide) and poly(DL-lactic acid) cationic nanoparticles for controlled delivery of plasmid DNA

The objective of this study was to investigate the effect of formulation parameters (i.e. polymer molecular weight and homogenization speed) on various physicochemical and biological properties of cationic nanoparticles. Cationic nanoparticles were prepared using different molecular weights of poly(DL-lactide-co-glycolide) (PLGA) and poly(DL-lactic acid) (PLA) by double emulsion solvent evaporation at two different homogenization speeds, and were characterized in terms of size, surface charge, morphology, loading efficiency, plasmid release, plasmid integrity, cytotoxicity, and transfection efficiency. Cationic surfactant, cetyltrimethylammonium bromide (CTAB), was used to provide positive charge on the surface of nanoparticles. Reporter plasmid gWIZ Beta-gal was loaded on the surface of nanoparticles by incubation. Use of higher homogenization speed and lower molecular weight polymer led to a decrease in mean particle size, increase in zeta potential, increase in plasmid loading efficiency, and a decrease in burst release. The nanoparticles displayed good morphology as evident from scanning electron micrographs. In vitro cytotoxicity study by MTT assay showed a low toxicity. Structural integrity of the pDNA released from nanoparticles was maintained. Transfecting human embryonic kidney (HEK293) cells with nanoparticles prepared from low molecular weight PLGA and PLA resulted in an increased expression of beta-galactosidase as compared to those prepared from high molecular weight polymer. Our results demonstrate that the PLGA and PLA cationic nanoparticles can be used to achieve prolonged release of pDNA, and the plasmid release rate and transfection efficiency are dependent on the formulation variables.     

Preparation and in vitro evaluation of actively targetable nanoparticles for SN-38 delivery against HT-29 cell lines

SN-38 (7-ethyl-10-hydroxycamptothecin) is the active metabolite of irinotecan, which is 100-to 1000-fold more cytotoxic than irinotecan. Nevertheless, extreme hydrophobicity of SN-38 has prevented its clinical use. One way of improving the solubility and stability of SN-38 is to formulate the drug into nanoparticles. Folic acid has been widely used as a targeting moiety for various anticancer drugs. For folate-receptor–targeted anticancer therapy, SN-38 nanoparticles were produced using poly-lactide-co-glycolide–polyethylene glycol–folate (PLGA-PEG-FOL) conjugate by emulsification/solvent evaporation method. The FOL-conjugated di-block copolymer was synthesized by coupling the PLGA-PEG-NH₂ di-block copolymer with an activated folic acid. The conjugates were used for the formation of SN-38 nanoparticles with an average size of 200 nm in diameter. The SN-38 targeted nanoparticles showed a greater cytotoxicity against HT-29 cancer cells than SN-38 nontargeted nanoparticles. These results suggested that folate-targeted nanoparticles could be a potentially useful delivery system for SN-38 as an anticancer agent.From the Clinical EditorSN-38 is the active metabolite of the chemotherapy agent irinotecan, which is 100-1000 fold more cytotoxic than irinotecan, but its extreme hydrophobicity has prevented its clinical use. In this paper, the authors present a nanotechnology-based approach targeting the folate-receptor with SN-38 loaded nanoparticles, demonstrating stronger cytotoxicity against HT-29 cancer cells than with control nanoparticles.     

Targeted delivery of 5-fluorouracil to HT-29 cells using high efficient folic acid-conjugated nanoparticles

Abstract

The incorporation of a high percentage of targeting molecules into drug delivery system is one of the important methods for improving efficacy of targeting therapeutic drugs to cancer cells. PLGA-based drug delivery carriers with folic acid (FA) as targeting molecule have a low targeting efficiency due to a low FA conjugation ratio. In this work, we fabricated a FA-conjugated PLGA system using a crosslinker 1, 3-diaminopropane and have achieved a high conjugation ratio of 46.7% (mol/mol). The as-prepared PLGA-based biomaterial was used to encapsulate therapeutic drug 5-fluorouracil (5-FU) into nanoparticles. In the in vitro experiments, an IC₅₀ of 5.69?µg/mL has been achieved for 5-FU loaded PLGA-1, 3-diaminopropane-folic acid nanoparticles on HT-29 cancer cells and is significantly lower than that of 5-FU and 5-FU loaded PLGA nanoparticles which only have an IC₅₀ of 22.9 and 14.17?µg/mL, respectively. The fluorescent microscopy images showed that nanoparticles with FA are largely taken up by HT-29 cancer cells and the targeting nanoparticles have more affinity to cancer cells than the pure drugs and untreated nanoparticles. Therefore, the 1, 3-diaminopropane can facilitate the conjugation of FA to PLGA to form a novel polymer and 5-FU loaded PLGA-1, 3-diaminopropane-folic acid nanoparticles can be a highly efficient system for specific delivery of drugs to cancer cells.     

Biological characterization of folic acid-conjugated poly(H2NPEGCA-co-HDCA) nanoparticles in cellular models

The folate receptor (FR) is a highly selective tumor marker over expressed in many human cancers and it constitutes a useful target for tumor-specific drug delivery. Thus, the conjugation of folic acid to different drugs or drug carriers may enhance the delivery of the therapeutic agent to FR-positive tumor cells. The aim of this study was to investigate the interactions of folate-conjugated polyalkylcyanoacrylate nanoparticles with tumor cells overexpressing the FR. For this purpose, nanoparticles were prepared by nanoprecipitation of the poly[aminopoly(ethylene glycol) cyanoacrylate-co-hexadecyl cyanoacrylate] [poly(H2NPEGCA-co-HDCA)] copolymer and labeled with the hydrophobic fluorescent dye nile red. Nile red-loaded nanoparticles were then conjugated to folic acid via the PEG terminal amino groups. Four human cancer cell lines were then tested by western blot in order to evaluate the FR expression levels. KB3-1 cell line showed the higher expression level, while MCF-7 cells were taken as a control. After measuring the cytotoxicity of the nanoparticles on these two cell lines, fluorescent folate-nanoparticles were incubated with them and the cellular uptake was evaluated by confocal microscopy and flow cytometry. KB3-1 cells showed a greater nanoparticle internalization, when compared to MCF-7 cells.     

Hydrophobically modified carboxymethyl chitosan nanoparticles targeted delivery of paclitaxel

Specific targeting of tumor cells to achieve higher drug levels in tumor tissue and to overcome the side effects is the major goal in cancer therapy. Nanoparticles encapsulating a hydrophobic core in their nanoreservoir structure were developed as a carrier for a water-insoluble drug, paclitaxel. In the present study, target-oriented nanoparticles based on biodegradable O-carboxymethyl chitosan modified with stearic acid. The surface of the nanoparticles was modified by covalent attachment of folic acid (FA) by simple carbodimide reaction to achieve tumor cell targeting property. Nanoparticles were prepared by the sonication method without involving any surfactants/emulsifiers. The nanoparticles were characterized by various state-of-the-art techniques, including laser light scattering for particles size distribution, field emission scanning electron microscopy and transmission electron microscope for surface morphology. The drug release property and the cytotoxicity of the drug loaded nanoparticles to both cancerous and noncancerous cells were evaluated in cell culture system. To our knowledge, this is the first study demonstrating a FA modified hydrophobically chitosan with paclitaxel-loaded nanoparticles targeting of folate receptor overexpressing cancer cells.     

Preparation,characterization, and <Emphasis Type="Italic">in vivo</Emphasis> evaluation of mitoxantrone-loaded,folate-conjugated albumin nanoparticles

Folic acid was covalently conjugated to bovine serum albumin nanoparticles (BSANP) to target the nanoparticles to SKOV3 cells expressing folate receptors. Mitoxantrone was incorporated into the folate-conjugated albumin nanoparticles, and the final nanoparticle size was 68 nm, as measured by a laser light scattering particle analyzer. The cytotoxic activity of mitoxantrone- loaded, folate-conjugated albumin nanoparticles (MTO-BSANP-folate), which was quantitated by ³H-thymidine incorporation, was higher than mitoxantrone-loaded BSANP (MTO-BSANP) and MTO solution, and could be inhibited by free folic acid. MTO-BSANPfolate may be endocytosed via the folate receptor on the surface of SKOV3 cells. MTO-BSANPfolate also inhibited tumor growth better than the MTO-BSANP and MTO solution in vivo. These results indicate that folate-conjugated BSANP may have therapeutic potential as a vector for anticancer drugs in cancer chemotherapy.     

Optimization of self-assembling properties of fatty acids grafted to methoxy poly(ethylene glycol) as nanocarriers for etoposide

The objective of this work was to study the effect of fatty acid chain length grafted to methoxy poly(ethylene glycol) (mPEG) on self assembling properties of micelles for etoposide delivery. Three amphiphilic copolymers were synthesized using mPEG, myristic acid, stearic acid and behenic acid through an esteric linkage. The particle size and zeta potential of the micelles were determined by the dynamic light scattering method. Etoposide was loaded into micelles by film casting using various drug/polymer ratios. Drug release was studied by the dialysis method. The structure of copolymers was confirmed by (1)H NMR and FTIR. Central micellar concentration (CMC) measurements showed that the longer hydrophobic chains formed more thermodynamically stable micelles. Among the prepared copolymers, etoposide showed the highest solubility in the mPEG-behenic copolymer. Drug loading efficiency depended on the hydrophobic chain length and drug/polymer ratio. The highest drug loading efficiency was found in mPEG-myristic micelles with 1:20 drug/polymer ratio. Micelles released 80 % of loaded drug within about 5 h.     

Biological characterization of folic acid-conjugated poly(H2NPEGCA-co-HDCA) nanoparticles in cellular models

The folate receptor (FR) is a highly selective tumor marker over expressed in many human cancers and it constitutes a useful target for tumor-specific drug delivery. Thus, the conjugation of folic acid to different drugs or drug carriers may enhance the delivery of the therapeutic agent to FR-positive tumor cells. The aim of this study was to investigate the interactions of folate-conjugated polyalkylcyanoacrylate nanoparticles with tumor cells overexpressing the FR. For this purpose, nanoparticles were prepared by nanoprecipitation of the poly[aminopoly(ethylene glycol) cyanoacrylate-co-hexadecyl cyanoacrylate] [poly(H₂NPEGCA-co-HDCA)] copolymer and labeled with the hydrophobic fluorescent dye nile red. Nile red-loaded nanoparticles were then conjugated to folic acid via the PEG terminal amino groups. Four human cancer cell lines were then tested by western blot in order to evaluate the FR expression levels. KB3-1 cell line showed the higher expression level, while MCF-7 cells were taken as a control. After measuring the cytotoxicity of the nanoparticles on these two cell lines, fluorescent folate-nanoparticles were incubated with them and the cellular uptake was evaluated by confocal microscopy and flow cytometry. KB3-1 cells showed a greater nanoparticle internalization, when compared to MCF-7 cells.     

Folic acid conjugated mPEG-PEI600 as an efficient non-viral vector for targeted nucleic acid delivery

In this study we describe a novel polymer, mPPS-FA, synthesized as a potential gene transfer vector. To complete mPPS-FA, folic acid was conjugated to a backbone (named mPPS) consisting of a copolymer of methyl PEG-2000, PEI-600, and sebacoyl chloride. (1)H NMR, FT-IR, and UV spectroscopy were used to characterize the structure of mPPS-FA. It was revealed that mPPS-FA holds the ability to bind plasmid DNA yielding positively charged particles (polyplexes). Dynamic light scattering (DLS) and TEM techniques were used to study the size and morphology of the formed mPPS-FA/DNA nanocomplexes. The mPPS-FA/DNA nanoparticles exhibited low cytotoxicity as transfection of B16-F0, U87MG, CHO-1, and Ho-8910 cells produced >80% viability indicating low cytotoxicity of the polymer. The ability of mPPS-FA to deliver EGFP plasmid to melanoma B16-F0, U87, CHO-1, Ho-8910, and A549 cells was investigated in vitro as compared to the lipid-based transfection agent Lipofectamine2000 and Linear PEI 22 kDa (L-PEI 22 kDa). We found that mPPS-FA/DNA complexes yielded the highest GFP transfection efficiency in B16-F0, U87, CHO-1, and Ho-8910 cells, which all highly express folate receptors (FR), at an mPPS-FA/DNA ratio (w/w) of 15. Furthermore, the transfection of mPPS-FA/DNA complexes in CHO-1 cells could be competitively blocked by free folic acid molecules. In contrast, in low FR expressing A549 cells, mPPS-FA showed similar low transfection efficiency as mPPS. Taken together, mPPS-FA showed the highest efficiency in vitro and the potential to be developed as a nonviral gene carrier.     

Surfactant-free poly(lactide-co-glycolide) nanoparticles for improving in vitro anticancer efficacy of tetrandrine

The objective of this study was to improve the efficacy of a natural compound tetrandrine against cancer by designing surfactant-free poly(lactic-co-glycolic acid) (PLGA) nanoparticles as drug carriers for tetrandrine. Nanoparticles were prepared from PLGA via the nano-precipitation method with or without the presence of surfactant poly(vinyl alcohol) (PVA) to encapsulate tetrandrine. Tetrandrine-loaded surfactant-free PLGA nanoparticles had an average particle size of 169.3?nm and morphology similar to the PLGA nanoparticles prepared using PVA as the surfactant. Tetrandrine-loaded surfactant-free PLGA nanoparticles could retard drug release in phosphate buffered saline (PBS) at pH 7.4 and the cumulative release of tetrandrine reached up to 68.33% over a period of 120?h. A549 cell line was used as the model cancer cells to investigate anticancer capability of tetrandrine-loaded surfactant-free PLGA nanoparticles via apoptosis assay, cytotoxicity and lysosome injury studies. The results showed that tetrandrine-loaded surfactant-free PLGA nanoparticles could effectively reduce cell viability and synergistically enhance tetrandrine-induced cell apoptosis.     

Development,optimization and in vitro evaluation of oxaliplatin loaded nanoparticles in non-small cell lung cancer

BackgroundPlatinum-based chemotherapy in non-small cell lung cancer (NSCLC) has been demonstrated as a promising approach by many researchers. However, due to low bioavailability and several side effects, drug targeting to lungs by intravenous administration is not a common route of administration.ObjectiveIn this study, oxaliplatin loaded polycaprolactone (PCL) nanoparticles were prepared to overcome the limitations of the drug. 3³ factorial design was used to evaluate the combined effect of the selected variables on the nanoparticle characteristics and to optimize oxaliplatin loaded PCL nanoparticles.MethodsThe factorial design was used to study the influence of three different independent variables on the response of nanoparticle particle size, polydispersity index (PDI), zeta potential, and encapsulation efficiency. The cellular uptakes of oxaliplatin loaded nanoparticles with different molecular weights of PCL were evaluated. Moreover, optimized nanoparticles were evaluated for their efficacy in non-small lung cancer using the SK-MES-1 cell line.ResultsIn factorial design, it is found that the homogenization speed and surfactant ratio represented the main factors influencing particle size and PDI and did not seem to depend on the PCL ratio. While the cytotoxicity of free oxaliplatin and oxaliplatin loaded nanoparticles were similar in low drug doses (2.5 and 25 μg/mL), the cytotoxicity of oxaliplatin loaded nanoparticles on SK-MES-1 cell was found higher in higher doses (p < 0.05). Moreover, oxaliplatin nanoparticles formulated with different molecular weights of PCL did not show significant differences in cellular uptake in 1 h and 2 h. However, the uptake of PCL₈₀₀₀₀ NPs was found significantly greater than free oxaliplatin at 4 h (p < 0.05).ConclusionHence, the development of oxaliplatin loaded PCL nanoparticles can be a useful approach for effective NSCLC therapy.Graphical abstract Open in a separate windowDevelopment, optimization and in vitro evaluation of oxaliplatin loaded nanoparticles in non-small cell lung cancer     

Bupivacaine-loaded biodegradable poly(lactic-co-glycolic) acid microspheres I. Optimization of the drug incorporation into the polymer matrix and modelling of drug release

Bupivacaine has been encapsulated by solvent evaporation method based on O/W emulsion, using poly(DL-lactic-co-glycolic) acid (PLGA) 50:50. The particle size can be controlled by changing stirring rate and polymer concentration. The encapsulation efficiency was affected by polymer concentration and burst effect of bupivacaine released from particles was affected by drug/polymer mass ratio. Orthogonal design was used to optimize the formulation according to drug content, encapsulation efficiency and burst effect. The dissolution profile and release model were evaluated with two different bupivacaine microspheres (bupi-MS) groups including low drug loading (6.41%) and high drug loading (28.92%). It was observed that drug release was affected by drug loading especially the amount of drug crystal attached on surface of bupi-MS. The drug release profile of low drug loaded bupi-MS agreed with Higuchi equation and that of high drug loaded bupi-MS agreed with first order equation.     

A novel truncated basic fibroblast growth factor fragment-conjugated poly (ethylene glycol)-cholesterol amphiphilic polymeric drug delivery system for targeting to the FGFR-overexpressing tumor cells

Targeted uptake of therapeutic nanoparticles in tumor cells-specific manner represents a potentially powerful technology in cancer therapy. In present study, we proposed a drug delivery system formulated with biocompatible and biodegradable cholesterol-block-poly (ethylene glycol) (Chol-PEG(2000)-COOH) polymer. And the surface of the polymer was chemically linked with truncated bFGF fragments (tbFGF). The tbFGF could recognize fibroblast growth factor receptors (FGFR) that are highly expressed by a variety of human cancer cells. The micelles had a size distribution of about 10-50 nm and significantly enhanced the cytotoxicity of paclitaxel to LL/2 cells as demonstrated by MTT test (IC??=0.21 μg/mL for tbFGF conjugated Chol-PEG(2000)-COOH micelles (tbFGF-M-PTX) versus 26.43 μg/mL for free paclitaxel, respectively). Flow cytometry revealed the cellular uptake of rhodamine B encapsulated in the tbFGF-conjugated micelles was increased by 6.6-fold for HepG2, 6.2-fold for A549, 2.9-fold for C26 and 2.7-fold for LL/2 tumor cells, respectively, compared with micelles without tbFGF. The fluorescence spectroscopy images further demonstrated that the tbFGF conjugated micelles could specifically bind to the tumor cells that over-expressed FGFRs and then release rhodamine B into the cytoplasm. Our results suggest the tbFGF conjugated Chol-PEG(2000)-COOH micelles have great potential application for tumor targeting therapy.     

Preparation of folate-modified pullulan acetate nanoparticles for tumor-targeted drug delivery

The purpose of this work was to develop a novel nano-carrier with targeting property to tumor. In this study, pullulan acetate (PA) was synthesized by the acetylation of pullulan to simplify the preparation technique of nanoparticles. Folic acid (FA) was conjugated to PA in order to improve the cancer-targeting activity. The products were characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy. Epirubicin-loaded nanoparticles were prepared by a solvent diffusion method. The loading efficiencies and EPI content increased with the amount of triethylamine (TEA) increasing in some degree. FPA nanoparticles could incorporate more epirubicin than PA nanoparticles. The folate-modified PA nanoparticles (FPA/EPI NPs) exhibited faster drug release than PA nanoparticles (PA/EPI NPs) in vitro. Confocal image analysis and flow cytometry test revealed that FPA/EPI NPs exhibited a greater extent of cellular uptake than PA/EPI NPs against KB cells over-expressing folate receptors on the surface. FPA/EPI NPs also showed higher cytotoxicity than PA/EPI NPs. The cytotoxic effect of FPA/EPI NPs to KB cells was inhibited by an excess amount of folic acid, suggesting that the binding and/or uptake were mediated by the folate receptor.     

Interaction of folate-conjugated human serum albumin (HSA) nanoparticles with tumour cells

Folic acid has been previously demonstrated to mediate intracellular nanoparticle uptake. Here, we investigated cellular uptake of folic acid-conjugated human serum albumin nanoparticles (HSA NPs). HSA NPs were prepared by desolvation and stabilised by chemical cross-linking with glutaraldehyde. Folic acid was covalently coupled to amino groups on the surface of HSA NPs by carbodiimide reaction. Preparation resulted in spherical HSA NPs with diameters of 239 ± 26 nm. As shown by size exclusion chromatography, 7.40 ± 0.90 μg folate was bound per mg HSA NPs. Cellular NP binding and uptake were studied in primary normal human foreskin fibroblasts (HFFs), the human neuroblastoma cell line UKF-NB-3, and the rat glioblastoma cell line 101/8 by fluorescence spectrophotometry, flow cytometry, and confocal laser scanning microscopy. Covalent conjugation of folic acid to HSA NPs increased NP uptake into cancer cells but not into HFFs. Free folic acid interfered with cancer cell uptake of folic acid-conjugated HSA NPs but not with uptake of folic acid-conjugated HSA NPs into HFFs. These data suggest that covalent linkage of folic acid can specifically increase cancer cell HSA NP uptake.     

Preparation of folate-modified pullulan acetate nanoparticles for tumor-targeted drug delivery

The purpose of this work was to develop a novel nano-carrier with targeting property to tumor. In this study, pullulan acetate (PA) was synthesized by the acetylation of pullulan to simplify the preparation technique of nanoparticles. Folic acid (FA) was conjugated to PA in order to improve the cancer-targeting activity. The products were characterized by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Epirubicin-loaded nanoparticles were prepared by a solvent diffusion method. The loading efficiencies and EPI content increased with the amount of triethylamine (TEA) increasing in some degree. FPA nanoparticles could incorporate more epirubicin than PA nanoparticles. The folate-modified PA nanoparticles (FPA/EPI NPs) exhibited faster drug release than PA nanoparticles (PA/EPI NPs) in vitro. Confocal image analysis and flow cytometry test revealed that FPA/EPI NPs exhibited a greater extent of cellular uptake than PA/EPI NPs against KB cells over-expressing folate receptors on the surface. FPA/EPI NPs also showed higher cytotoxicity than PA/EPI NPs. The cytotoxic effect of FPA/EPI NPs to KB cells was inhibited by an excess amount of folic acid, suggesting that the binding and/or uptake were mediated by the folate receptor.     

Poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles prepared by high pressure homogenization for paclitaxel chemotherapy

High pressure homogenization was employed in the current work to prepare poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) for controlled release of paclitaxel. The prepared drug-loaded PLGA NPs were found of spherical shape with a size of 200-300 nm. The drug encapsulation efficiency ranged from 34.8+/-1.6 to 62.6+/-7.9% depending on the homogenization pressure and cycles. Paclitaxel was released from the nanoparticles in a biphasic profile with a fast release rate in the first 3 days followed by a slow first-order release. A higher or comparable cytotoxicity against glioma C6 cells was found for the drug formulated in the PLGA NPs in comparison with the free drug Taxol. Confocal laser scanning microscopy (CLSM) evidenced internalization of the fluorescent coumarin 6-loaded PLGA NPs by the C6 cells. The freeze-dried nanoparticles were found to possess excellent water redispersability. The high pressure homogenization could be applied for large industrial scale production of nanoparticles for drug delivery.     

Haloperidol-loaded PLGA nanoparticles: systematic study of particle size and drug content

We have produced haloperidol-loaded PLGA/PLA nanoparticles by using two emulsification-solvent evaporation methods: homogenization and sonication. We have established how five independent processing parameters and two materials characteristics control the particle size and drug content. The interdependencies between processing and materials parameters and the subsequent nanoparticle characteristics are discussed in terms of underlying scientific principles that are broadly applicable to the production of drug-loaded polymer nanoparticles. This level of understanding should quicken the pace of designing protocols for making new drug-PLGA nanoparticles. It was determined that the particle size of haloperidol-loaded PLGA/PLA nanoparticles is effectively controlled by the amount of shear stress transferred from the energy source to the organic phase, which is strongly correlated to the following parameters: type of applied energy, aqueous phase volume, and polymer concentration in the organic solvent. The drug content of these nanoparticles is controlled by reducing the diffusion of the drug from the organic to the aqueous phase during the solvent evaporation stage of the preparation and by increasing the drug-polymer interactions. The following significantly inhibit drug diffusion: large particle size, higher polymer concentration and polymer molecular weight, and reducing the drug solubility in the aqueous phase by adjusting the pH. Specific drug-polymer interactions are engineered by optimizing the lactide to glycolide ratio (L:G ratio) and including specific polymer end groups. When optimized, the drug-loaded PLGA/PLA nanoparticles contain as much as 2.5% haloperidol.     

白藜芦醇PLGA长效注射微球的制备及工艺考察

目的采用乳化溶剂挥发法制备白藜芦醇聚乳酸羟基乙酸[poly(lactic-co-glycolic acid),PL-GA]长效微球,评价各因素对微球性质的影响。方法以微球的包封率、载药量、突释和粒径作为微球的质量评价指标,研究分散相与连续相的体积比、PLGA浓度、聚乙烯醇(polyvinyl alcohol,PVA)浓度、搅拌速度对微球性质的影响,并优化白藜芦醇PLGA微球的制备工艺。结果分散相与连续相的体积比为1∶50时,包封率高,但4 h突释量达到76%,当分散相与连续相体积比由1∶50提升到1∶150时,突释降低了22%;随着聚合物浓度的增加粒径明显增大,突释显著降低;理论载药量对粒径影响不大,在高载药量时突释显著减少;搅拌速度的增加使粒径减小,突释增加;PVA浓度的增加对粒径没有明显的影响,但当PVA的质量浓度从1 g.L-1增加到5 g.L-1时,包封率从93.57%降低到80.31%。结论分散相与连续相的体积比、PLGA浓度、PVA浓度、搅拌速度对微球性质有很大的影响。优化条件下制备的微球形态完整,载药量为(27.86±1.00)%,包封率为(93.57±2.87)%,平均粒径约为21.12μm。白藜芦醇PLGA微球体外释放25 d的累积释药率达(94.04±4.94)%,有望研制成1个月给药1次的给药系统。     

Selective targeting and degradation of doxorubicin-loaded folate-functionalized DNA nanocages

Selective targeting is a crucial property of nanocarriers used for drug delivery in cancer therapy. We generated biotinylated octahedral DNA nanocages functionalized with folic acid through bio-orthogonal conjugation chemistry. Molecular modelling indicated that a distance of about 2.5 nm between folic acid and DNA nanocage avoids steric hindrance with the folate receptor. HeLa cells, a folate receptor positive tumour cell line, internalize folate-DNA nanocages with efficiency greater than 40 times compared to cells not expressing the folate receptors. Functionalized DNA nanocages are highly stable, not cytotoxic and can be efficiently loaded with the chemotherapeutic agent doxorubicin. After entry into cells, doxorubicin-loaded nanoparticles are confined in vesicular structures, indicating that DNA nanocages traffic through the endocytic pathway. Doxorubicin release from loaded DNA cages, facilitated by low pH of endocytic vesicles, induces toxic pathways that, besides selectively killing folate receptor-positive cancer cells, leads to cage degradation avoiding nanoparticles accumulation inside cells.