Poly(lactide)–vitamin E derivative/montmorillonite nanoparticle formulations for the oral delivery of Docetaxel

Four systems of nanoparticles of biodegradable polymers were developed in this research for oral delivery of anticancer drugs with Docetaxel used as a model drug, which include the poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs), the poly(lactide)–vitamin E TPGS nanoparticles (PLA–TPGS NPs), the poly(lactic-co-glycolic acid)–montmorillonite nanoparticles (PLGA/MMT NPs) and the poly(lactide)–vitamin E TPGS/montmorillonite nanoparticles (PLA–TPGS/MMT NPs). Vitamin E TPGS stands for d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), which is a water-soluble derivative of natural vitamin E formed by esterification of vitamin E succinate with polyethylene glycol (PEG) 1000. The design was made to take advantages of TPGS in nanoparticle technology such as high emulsification effects and high drug encapsulation efficiency, and those in drug formulation such as high cellular adhesion and adsorption. MMT of similar effects is also a detoxifier, which may cure some side effects caused by the formulated drug. The drug-loaded NPs were prepared by a modified solvent extraction/evaporation method and then characterized for their MMT content, size and size distribution, surface charge and morphology, physical status and encapsulation efficiency of the drug in the NPs, and in vitro drug release profile. Cellular uptake of the coumarin 6-loaded NPs was investigated. In vitro cancer cell viability experiment showed that judged by IC₅₀, the PLA–TPGS/MMT NP formulation was found 2.89, 3.98, 2.12-fold more effective and the PLA–TPGS NP formulation could be 1.774, 2.58, 1.58-fold more effective than the Taxotere^® after 24, 48, 72 h treatment, respectively. In vivo PK experiment with SD rats showed that oral administration of the PLA–TPGS/MMT NP formulation and the PLA–TPGS NP formulation could achieve 26.4 and 20.6 times longer half-life respectively than i.v. administration of Taxotere^® at the same 10 mg/kg dose. One dose oral administration of the NP formulations could realize almost 3 week sustained chemotherapy in comparison of 22 h of i.v. administration of Taxotere^®. The oral bioavailability can be enhanced from 3.59% for Taxotere^® to 78% for the PLA–TPGS/MMT NP formulation and 91% for the PLA–TPGS NP formulation respectively. Oral chemotherapy by nanoparticles of biodegradable polymers is feasible.     

Covalent attachment of Mn-porphyrin onto doxorubicin-loaded poly(lactic acid) nanoparticles for potential magnetic resonance imaging and pH-sensitive drug delivery

In this paper, theranostic nanoparticles (MnP-DOX NPs) were fabricated by conjugating Mn-porphyrin onto the surface of doxorubicin (DOX)-loaded poly(lactic acid) (PLA) nanoparticles (DOX NPs) for potential T₁ magnetic resonance imaging and pH-sensitive drug delivery. An in vitro drug release study showed that the release rate of DOX from MnP-DOX NPs was slow at neutral pH but accelerated significantly in acidic conditions. It was found that MnP-DOX NPs could be easily internalized by HeLa cells and effectively suppressed the growth of HeLa cells and HT-29 cells due to the accelerated drug release in acidic lysosomal compartments. Magnetic resonance imaging (MRI) scanning analysis demonstrated that MnP-DOX NPs had much higher longitudinal relaxivity in water (r₁ value of 27.8 mM^?1 s^?1 of Mn³⁺) than Mn-porphyrin (Mn(III)TPPS3NH₂; r₁ value of 6.70 mM^?1 s^?1 of Mn³⁺), behaving as an excellent contrast agent for T₁-weighted MRI both in vitro and in vivo. In summary, such a smart and promising nanoplatform integrates multiple capabilities for effective cancer diagnosis and therapy.     

Polymeric nanoparticles for pulmonary protein and DNA delivery

Polymeric nanoparticles (NPs) are promising carriers of biological agents to the lung due to advantages including biocompatibility, ease of surface modification, localized action and reduced systemic toxicity. However, there have been no studies extensively characterizing and comparing the behavior of polymeric NPs for pulmonary protein/DNA delivery both in vitro and in vitro. We screened six polymeric NPs: gelatin, chitosan, alginate, poly(lactic-co-glycolic) acid (PLGA), PLGA–chitosan and PLGA–poly(ethylene glycol) (PEG), for inhalational protein/DNA delivery. All NPs except PLGA–PEG and alginate were <300 nm in size with a bi-phasic core compound release profile. Gelatin, PLGA NPs and PLGA–PEG NPs remained stable in deionized water, serum, saline and simulated lung fluid (Gamble’s solution) over 5 days. PLGA-based NPs and natural polymer NPs exhibited the highest cytocompatibility and dose-dependent in vitro uptake, respectively, by human alveolar type-1 epithelial cells. Based on these profiles, gelatin and PLGA NPs were used to encapsulate plasmid DNA encoding yellow fluorescent protein (YFP) or rhodamine-conjugated erythropoietin (EPO) for inhalational delivery to rats. Following a single inhalation, widespread pulmonary EPO distribution persisted for up to 10 days while increasing YFP expression was observed for at least 7 days for both NPs. The overall results support both PLGA and gelatin NPs as promising carriers for pulmonary protein/DNA delivery.     

PLA2G2A polymorphisms are associated with metabolic syndrome and type 2 diabetes mellitus. Results from the genetics of atherosclerotic disease Mexican study

The secretory phospholipase A₂ II A (sPLA₂-IIA) encoded by PLA2G2A gene hydrolyzes phospholipids liberating free fatty acids (FFAs) and lysophospholipids. If lipolysis exceeds lipogenesis, the free fatty acids undergo a continuous release into circulation. A sustained excessive increase in this release contributes to metabolic disease. The aim of the present study was to evaluate the role of PLA2G2A gene polymorphisms as susceptibility markers for metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) in Mexican population. Three PLA2G2A gene polymorphisms (rs876018, rs3753827 and rs11573156) were genotyped by 5′ exonuclease TaqMan assays in a group of 338 patients with T2DM, 460 individuals with MetS and 366 healthy controls. Under codominant 1 (codom1), dominant (dom) and additive (add) models adjusted by age, gender, body mass index (BMI), smoking habit, and hypertension, the rs876018 T allele was associated with increased risk of MetS [Odds Ratio (OR) = 1.66, P_codom1 = 0.005; OR = 1.67, P_dom = 0.003; OR = 1.49, P_add = 0.005] as compared to controls. On the other hand, under several models adjusted by the same variables, the rs3753827 A (OR = 1.52, P_codom1 = 0.039 and OR = 1.49, P_dom = 0.039) and rs11573156C alleles (OR = 6.46, P_codom1 = 0.013; OR = 6.70, P_codom2 = 0.009; OR = 6.65, P_dom = 0.009) were associated with increased risk of T2DM when compared with controls. In addition, the rs876018 T allele was associated with hypercholesterolemia (P_dom = 0.017, P_add = 0.009) and risk of subclinical atherosclerosis (SA) (P_dom = 0.041) in MetS when compared with controls. Also, this allele was associated with SA in T2DM patients (P_dom = 0.007). The TAG haplotype was significantly associated with increased risk of MetS (OR = 1.54, P = 0.006). Results suggest that PLA2G2A polymorphisms are involved in the risk of developing MetS and T2D and are associated with SA in this group of patients.     

In vivo evaluation of safety and efficacy of self-assembled nanoparticles for oral insulin delivery

A variety of approaches have been studied in the past to overcome the problems encountered with the oral delivery of insulin, but with little success. In this study, self-assembled nanoparticles (NPs) with a pH-sensitive characteristic were prepared by mixing the anionic poly-γ-glutamic acid solution with the cationic chitosan solution in the presence of MgSO₄ and sodium tripolyphosphate. The in vitro results found that the transport of insulin across Caco-2 cell monolayers by NPs appeared to be pH-dependent; with increasing pH, the amount of insulin transported decreased significantly. An in vivo toxicity study was performed to establish the safety of the prepared NPs after oral administration. Additionally, the impact of orally administered NPs on the pharmacodynamics (PD) and pharmacokinetics (PK) of insulin was evaluated in a diabetic rat model. The in vivo results indicated that the prepared NPs could effectively adhere on the mucosal surface and their constituted components were able to infiltrate into the mucosal cell membrane. The toxicity study indicated that the NPs were well tolerated even at a dose 18 times higher than that used in the PD/PK study. Oral administration of insulin-loaded NPs demonstrated a significant hypoglycemic action for at least 10 h in diabetic rats and the corresponding relative bioavailability of insulin was found to be 15.1 ± 0.9%. These findings suggest that the NPs prepared in the study are a promising vehicle for oral delivery of insulin.     

An animal model of PDH deficiency using AAV8-siRNA vector-mediated knockdown of pyruvate dehydrogenase E1α

We evaluated the feasibility of self-complementary adeno-associated virus (scAAV) vector-mediated knockdown of the pyruvate dehydrogenase complex using small interfering RNAs directed against the E1α subunit gene (PDHA1). AAV serotype 8 was used to stereotaxically deliver scAAV8-si3-PDHA1-Enhanced Green Fluorescent Protein (knockdown) or scAAV8-EGFP (control) vectors into the right striatum and substantia nigra of rats. Rotational asymmetry was employed to quantify abnormal rotation following neurodegeneration in the nigrostriatal system. By 20 weeks after surgery, the siRNA-injected rats exhibited higher contralateral rotation during the first 10 min following amphetamine administration and lower 90-min total rotations (p ≤ 0.05). Expression of PDC E1α, E1β and E2 subunits in striatum was decreased (p ≤ 0.05) in the siRNA-injected striatum after 14 weeks. By week 25, both PDC activity and expression of E1α were lower (p ≤ 0.05) in siRNA-injected striata compared to controls. E1α expression was associated with PDC activity (R² = 0.48; p = 0.006) and modestly associated with counterclockwise rotation (R² = 0.51;p = 0.07). The use of tyrosine-mutant scAAV8 vectors resulted in ~ 17-fold increase in transduction efficiency of rat striatal neurons in vivo. We conclude that scAAV8-siRNA vector-mediated knockdown of PDC E1α in brain regions typically affected in humans with PDC deficiency results in a reproducible biochemical and clinical phenotype in rats that may be further enhanced with the use of tyrosine-mutant vectors.     

Evaluation of polyethylene glycol precipitation as screening test for macroprolactinemia using Architect immunoanalyser

We performed the polyethylene glycol (PEG) precipitation test to determine the prevalence of macroprolactinemia in 172 hyperprolactinemic subjects with prolactin (PRL) levels > 700 mIU/l. PRL was measured by Architect i2000 (Abbott Diagnostics) both in serum and in supernatant obtained after PEG. We used the PRL recovery percentage (R%) as interpretative criterion of PEG test and we estimated a prevalence of macroprolactinemia of 21.5% (R% ≤ 40%), whereas 74.4% of subjects showed a true hyperprolactinemia (R% ≥ 60%). In true hyperprolactinemic subjects PRL levels obtained before and after PEG showed a good correlation (Pearson coefficient, R = 0.995); in macroprolactinemic individuals no correlation was found. The PEG test was also performed in 50 normoprolactinemic subjects and a new PRL reference interval was obtained: 64–453 mIU/l. In this case the macroprolactinemic subjects (hyperprolactinemic presenting a normal PRL value after PEG) were 20.3% whereas 79.7% showed still elevated PRL levels. In 35 females we were also able to evaluate the symptoms and the pituitary imaging findings: no significant differences between macroprolactinemic (N = 11) and true hyperprolactinemic (N = 24) subjects were found. In conclusion, the PEG test appears to be simple, reproducible and absolutely necessary for diagnostics of hyperprolactinemia.     

Complexes leucoplaquettaires en tant que marqueur d’activation dans les concentrés plaquettaires standards

ObjectivesSeveral in vitro laboratory tests to assess the quality control of platelet concentrates (PC) are available. Some of them have a good correlation with the platelet recovery index. To assess the quality control of standard PC prepared in our blood bank, we measured the blood gas and the degree of platelet activation.Materials and methodsSPC were prepared by the PRP method. Fifty-five SPC (45 SPC at day one of storage and 20 SPC at day five of storage) were analysed. Blood gas (pH, PO₂, PCO₂ and bicarbonate concentration) in the SPC were measured by blood gas automate. Platelet activation profile were determined by measuring the percentage of platelet expressing the CD62p (% CD62) and the percentage of platelet-leukocyte aggregate (% PLA).ResultsThe pH values of all studied SPC were comprised between 7.0 and 7.6. SPC at day 1 of storage have a significantly higher pH than those at day 5 of storage (7.5 ± 0.05 versus 7.3 ± 0.14; p < 0.001). The % CD62p were higher in SPC at day five compared to the SCP at day one without reaching a statistical significance (28.4 ± 15% versus 24.3 ± 9.7%, p = 0.052). The percentage of PLA were higher in SPC at day one compared to SCP at day five although this difference is not statistically significant (22.2 ± 7.5% versus 17.9 ± 8.0%; p = 0.23).ConclusionPreparation and storage procedure adopted in our centre did not significantly affect the quality SPC. Our study is the first to assess the PLA in PC. Studies assessing the PLA are warranted to appreciate the clinical impact of this parameter.     

PEGylated PEI-based biodegradable polymers as non-viral gene vectors

Novel functional biodegradable gene vectors, poly(l-succinimide)-g-polyethylenimines-g-poly(ethylene glycol) (PSI-g-PEI-g-PEGs) were synthesized by conjugating methoxy poly(ethylene glycol) (mPEG, M_w = 750 Da) to PEI segments (M_w = 800 Da) of PSI-g-PEI. The physicochemical properties of PSI-g-PEI-g-PEGs, including buffering capability, pDNA binding ability, cytotoxicity, zeta potential and the particle size of polymer/pDNA complexes, were explored. The influence of PEGylation was discussed based on a comparative study of PSI-g-PEI-g-PEGs, PSI-g-PEI and PEI25k (M_w = 25 kDa). SEM images revealed that PSI-g-PEI-g-PEG/pDNA particles have a regular shape with the diameter ranging from 70 to 170 nm. PEGylation could suppress the aggregation occurrence between complexes, resulting in a reduction of the polymer/pDNA complex size. PSI-g-PEI-g-PEGs exhibited remarkably lower cytotoxicity compared to PSI-g-PEI and PEI25k. In 293T and HeLa cells, the obtained PSI-g-PEI-g-PEGs showed very high transfection efficiency compared to PEI25k. Fluorescent confocal microscopy demonstrated that PSI-g-PEI-g-PEGs could effectively transport pGL-3 plasmids into the nuclei of HeLa cells. Taking into account the continued high transfection efficacy and decreased toxicity after PEG modification, PSI-g-PEI-g-PEGs show great potential as the non-viral vectors for gene transfection.     

Simultaneous release of multiple molecules from poly(lactide-co-glycolide) nanoparticles assembled onto medical devices

Cell and tissue responses to implanted biomaterials often limit their effectiveness and lifetime. This is particularly true for materials implanted into the brain. We present here a new approach for the modification of materials to enable release of multiple agents, which might be useful in modulating tissue responses, without changing the properties of the underlying material, in this case, a silicon probe. Poly(lactide-co-glycolide) nanoparticles (NPs) were assembled onto silicon probe surfaces by electrostatic interactions. Charged NPs were fabricated by altering the properties of the surfactant. NPs formed with poly(ethylene-alt-maleic anhydride) (PEMA) were strongly negatively charged; these NPs assembled onto probes best when suspended at nearly physiological conditions (surface density ～ 83,600 ± 3000 particles/mm²). The percentage of surface area coverage by the NPs was estimated to be ～13% and was maintained over two weeks during constant exposure to PBS. Multiple fluorescent NP populations were attached to the same probe to allow visualization of simultaneous delivery of multiple agents by fluorescence microscopy. Release from NP coatings was reproducible and controllable. The distinct release profiles of each agent from the coatings were preserved upon attachment to the surfaces. The unique feature of this new system is that NPs encapsulating various molecules (i.e. drugs, proteins, or DNA) can be fabricated separately, in advance, and simply mixed prior to attachment. The versatility of this delivery system, therefore, makes it suitable for many applications.     

Static autoregulation in humans: a review and reanalysis

IntroductionCerebral autoregulation (CA) is a theoretical construct characterized by the relationship between mean arterial pressure (MAP) and cerebral blood flow (CBF). We performed a comprehensive literature search to provide an up-to-date review on the static relationship between MAP and CBF.MethodsThe results are based on 40 studies (49 individual experimental protocols) in healthy subjects between 18 and 65 years. Exclusion criteria were: a ΔMAP <5%, hypoxia/hyperoxia or hypo/hypercapnia, and unstable levels (<2 min stages). The partial pressure of arterial CO₂ (PaCO₂) was measured in a subset of the included studies (n = 28); therefore, CBF was also adjusted to account for small changes in PaCO₂.ResultsThe linear regression coefficient between MAP and CBF (or velocity) of 0.82 ± 0.77%ΔCBF/%ΔMAP during decreases in MAP (n = 23 experiments) was significantly different than the relationship of 0.21 ± 0.47%ΔCBF/%ΔMAP during increases (n = 26 experiments; p < 0.001). After correction for increases/decreases in PaCO₂, the slopes were not significantly different: 0.64 ± 1.16%ΔCBF/%ΔMAP (n = 16) and 0.39 ± 0.30%ΔCBF/%ΔMAP (n = 12) for increased vs. decreased MAP changes, respectively (p = 0.60).ConclusionThe autoregulatory ability of the cerebral circulation appears to be more active in buffering increases in MAP as compared to reductions in MAP. However, the statistical finding of hysteresis is lost following an attempt to correct for PaCO₂.     

Novel ultrasound contrast agent based on microbubbles generated from surfactant mixtures of Span 60 and polyoxyethylene 40 stearate

In this study, novel perfluorocarbon-filled microbubbles as ultrasound contrast agent were fabricated using ultrasonication of a surfactant mixture of sorbitan monostearate (Span 60) and polyoxyethylene 40 stearate (PEG40S) in aqueous media. The microbubbles generated from a 1:9 mixture of PEG40S/Span 60 exhibited an average diameter of 2.08 ± 1.27 μm. More than 99% of the microbubbles had a mean particle diameter less than 8 μm, indicating that they were appropriately sized for intravenous administration as ultrasound contrast agent. The stabilization mechanism of the microbubbles was investigated by the Langmuir–Blodgett technique including the measurements of surface pressure–area (π–A) isotherms and compression–decompression cycles with a two-dimensional monolayer of Span 60 and PEG40S. The dependence on molar fraction of PEG40S in π–A isotherms of mixed monolayers provided a strong evidence of interactions between the two microbubble-forming materials. It is suggested that the monolayer shell imparts good stability to the microbubbles by three means: (1) a low surface tension monolayer hinders dissolution through the reduction of surface tension, which introduces a mechanical surface pressure that counters the Laplace pressure; (2) the presence of a monolayer shell imparts a significant barrier to gas escaping from the core into the aqueous medium; and (3) encapsulation elasticity stabilizes microbubbles against diffusion-driven dissolution and explains the long shelf-life of microbubble contrast agent. The preliminary in vivo ultrasound imaging study showed that such stabilized microbubbles demonstrated excellent enhancement under grey-scale pulse inversion harmonic imaging and power Doppler imaging.     

Short-chain PEG molecules strongly bound to magnetic nanoparticle for MRI long circulating agents

This study developed an approach for the synthesis of magnetic nanoparticles coated with three different polyethylene glycol (PEG)-derived molecules. The influence of the coating on different properties of the nanoparticles was studied. Magnetite nanoparticles (7 and 12 nm in diameter) were obtained via thermal decomposition of a coordination complex as an iron precursor to ensure nanoparticle homogeneity in size and shape. Particles were first coated with meso-2,3-dimercaptosuccinic acid by a ligand exchange process to remove oleic acid, followed by modification with three distinct short-chain PEG polymers, which were covalently bound to the nanoparticle surface via 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride activation of the carboxylic acids. In all cases, colloidal suspensions had hydrodynamic sizes <100 nm and low surface charge, demonstrating the effect of PEG coating on the aggregation properties and steric stabilization of the magnetic nanoparticles. The internalization and biocompatibility of these materials in the HeLa human cervical carcinoma cell line were tested. Cells preincubated with PEG-coated iron nanoparticles were visualized outside the cells, and their biocompatibility at high Fe concentrations was demonstrated using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Finally, relaxivity parameters (r₁ and r₂) were used to evaluate the efficiency of suspensions as magnetic resonance imaging contrast agents; the r₂ value was similar to that for Resovist and up to four times higher than that for Sinerem, probably due to the larger nanoparticle size. The time of residence in blood of the nanoparticles measured from the relaxivity values, and the Fe content in blood was doubled for rats and rabbits due to the PEG on the nanoparticle surface. The results suggest that this PEGylation strategy for large magnetic nanoparticles (>10 nm) holds promise for biomedical applications.     

The influence of poly(ethylene oxide) grafting via siloxane tethers on protein adsorption

Amphiphilic PEO–silanes (a–c) having siloxane tethers of varying lengths with the general formula α-(EtO)₃Si–(CH₂)₂–oligodimethylsiloxane_n-block-poly(ethylene oxide)₈–OCH₃ [n = 0 (a), n = 4 (b), and n = 13 (c)] were grafted onto silicon wafers and resistance to adsorption of plasma proteins was measured. Distancing the PEO segment from the hydrolyzable triethoxysilane [(EtO)₃Si] grafting group by a oligodimethylsiloxane tether represents a new method of grafting PEO chains to surfaces. Properties of surfaces grafted with a–c were compared to surfaces grafted with a traditional PEO–silane containing a propyl spacer [(EtO)₃Si–(CH₂)₃–poly(ethylene oxide)₈–OCH₃, PEO control]. As the siloxane tether length increased, chain density of PEO–silanes grafted onto oxidized silicon wafers decreased and hydrophobicity of the PEO–silane increased which led to a decrease in surface hydrophilicity. Despite decreased surface hydrophilicity, resistance to the adsorption of bovine serum albumin (BSA) increased in the order: PEO control < a < b ≈ c and to human fibrinogen (HF) increased in the order: PEO control < a < b < c.     

Characterizing the inhibitory action of zinc oxide nanoparticles on allergic-type mast cell activation

The development of nanoparticles (NPs) for commercial products is undergoing a dramatic expansion. Many sunscreens and cosmetics now use zinc oxide (ZnO) or titania (TiO₂) NPs, which are effective ultraviolet (UV) filters. Zinc oxide topical creams are also used in mild anti-inflammatory treatments. In this study we evaluated the effect of size and dispersion state of ZnO and TiO₂ NPs, compared to “bulk” ZnO, on mast cell degranulation and viability.ZnO and TiO₂ NPs were characterized using dynamic light scattering and disc centrifugation. Rat basophilic leukaemia (RBL-2H3) cells and primary mouse bone marrow-derived mast cells (BMMCs) were exposed to ZnO and TiO₂ NPs of different sizes (25–200 nm) and surface coatings at concentrations from 1 to 200 μg/mL. The effect of NPs on immunoglobulin E (IgE)-dependent mast cell degranulation was assessed by measuring release of both β-hexosaminidase and histamine via colorimetric and ELISA assays. The intracellular level of Zn²⁺ and Ca²⁺ ions were measured using zinquin ethyl ester and Fluo-4 AM fluorescence probes, respectively. Cellular viability was determined using the soluble tetrazolium-based MTS colorimetric assay.Exposure of RBL-2H3 and primary mouse BMMC to ZnO NPs markedly inhibited both histamine and β-hexosaminidase release. This effect was both particle size and dispersion dependent. In contrast, TiO₂ NPs did not inhibit the allergic response. These effects were independent of cytotoxicity, which was observed only at high concentrations of ZnO NPs, and was not observed for TiO₂ NPs.The inhibitory effects of ZnO NPs on mast cells were inversely proportional to particle size and dispersion status, and thus these NPs may have greater potential than “bulk” zinc in the inhibition of allergic responses.     

Effects of molecular weight of grafted hyaluronic acid on wear initiation

Hyaluronic acid (HA) of different molecular weights (M_w) was grafted onto mica surfaces to study the effects of M_w on the conformation and wear protection properties of a grafted HA (gHA) layer in lubricin (LUB) and bovine synovial fluid (BSF) using a surface forces apparatus. The M_w of gHA had significant effects on the wear pressure (P_w), at which point the wear initiates. Increasing the gHA M_w from 51 to 2590 kDa increased P_w from 4 to 8 MPa in LUB and from 15 to 31 MPa in BSF. The 2590 kDa gHA in BSF had the best wear protection (P_w ∼ 31 MPa), even though it exhibited the highest friction coefficient (μ ∼ 0.35), indicating that a low μ does not necessarily result in good wear protection, as is often assumed. The normal force profile indicated that BSF confines the gHA structure, making it polymer brush-like, commonly considered as an excellent structure for boundary lubrication.     

Biofilm formation on bone grafts and bone graft substitutes: Comparison of different materials by a standard in vitro test and microcalorimetry

We analyzed the initial adhesion and biofilm formation of Staphylococcus aureus (ATCC 29213) and S. epidermidis RP62A (ATCC 35984) on various bone grafts and bone graft substitutes under standardized in vitro conditions. In parallel, microcalorimetry was evaluated as a real-time microbiological assay in the investigation of biofilm formation and material science research. The materials β-tricalcium phosphate (β-TCP), processed human spongiosa (Tutoplast?) and poly(methyl methacrylate) (PMMA) were investigated and compared with polyethylene (PE). Bacterial counts (log₁₀ cfu per sample) were highest on β-TCP (S. aureus 7.67 ± 0.17; S. epidermidis 8.14 ± 0.05) while bacterial density (log₁₀ cfu per surface) was highest on PMMA (S. aureus 6.12 ± 0.2, S. epidermidis 7.65 ± 0.13). Detection time for S. aureus biofilms was shorter for the porous materials (β-TCP and processed human spongiosa, p < 0.001) compared to the smooth materials (PMMA and PE), with no differences between β-TCP and processed human spongiosa (p > 0.05) or PMMA and PE (p > 0.05). In contrast, for S. epidermidis biofilms the detection time was different (p < 0.001) between all materials except between processed human spongiosa and PE (p > 0.05). The quantitative analysis by quantitative culture after washing and sonication of the material demonstrated the importance of monitoring factors like specific surface or porosity of the test materials. Isothermal microcalorimetry proved to be a suitable tool for an accurate, non-invasive and real-time microbiological assay, allowing the detection of bacterial biomass without removing the biofilm from the surface.     

Glycyrrhetinic acid-modified poly(ethylene glycol)–b-poly(γ-benzyl l-glutamate) micelles for liver targeting therapy

Liver targeted micelles were successfully constructed via self-assembly of glycyrrhetinic acid (GA)-modified poly(ethylene glycol)–b-poly(γ-benzyl l-glutamate) (GA–PEG–PBLG) block co-polymers, which were fabricated via ring opening polymerization of γ-benzyl l-glutamate N-carboxyanhydride monomer initiated by GA-modified PEG. The in vivo biodistribution and the in vitro cellular uptake of these micelles were investigated. The results showed that the relative uptake of doxorubicin (DOX)-loaded micelles (DOX/GA–PEG–PBLG) in liver was much higher than in other tissues, and the resulting DOX concentration in liver was about 2.2-fold higher than that from the micelles without modification by GA. Moreover, the cellular uptake study demonstrated that the introduction of GA to the micelles could significantly increase the affinity for human hepatic carcinoma 7703 cells, which induced a 3.7-fold higher endocytosis than unmodified ones. The cytotoxicity of DOX/GA–PEG–PBLG micelles (IC₅₀ 47 ng ml^?1) was much higher than that of free DOX (IC₅₀ 90 ng ml^?1). These results indicate that GA-modified micelles have great potential in liver targeting therapy.     

Antifungal activity of silver nanoparticles against Candida spp.

The antifungal activity of the silver nanoparticles (NPs) prepared by the modified Tollens process was evaluated for pathogenic Candida spp. by means of the determination of the minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and the time-dependency of yeasts growth inhibition. Simultaneously the cytotoxicity of the silver NPs to human fibroblasts was determined. The silver NPs exhibited inhibitory effect against the tested yeasts at the concentration as low as 0.21 mg/L of Ag. The inhibitory effect of silver NPs was enhanced through their stabilization and the lowest MIC equal to 0.05 mg/L was determined for silver NPs stabilized by sodium dodecyl sulfate against Candida albicans II. The obtained MICs of the silver NPs and especially of the stabilized silver NPs were comparable and in some cases even better than MICs of the conventional antifungal agents determined by E-test. The silver NPs effectively inhibited the growth of the tested yeasts at the concentrations below their cytotoxic limit against the tested human fibroblasts determined at a concentration equal to 30 mg/L of Ag. In contrast, ionic silver inhibited the growth of the tested yeasts at the concentrations comparable to the cytotoxic level (approx. 1 mg/L) of ionic silver against the tested human fibroblasts.     

Material properties of components in human carotid atherosclerotic plaques: A uniaxial extension study

Computational modelling to calculate the mechanical loading within atherosclerotic plaques has been shown to be complementary to defining anatomical plaque features in determining plaque vulnerability. However, its application has been partially impeded by the lack of comprehensive knowledge about the mechanical properties of various tissues within the plaque. Twenty-one human carotid plaques were collected from endarterectomy. The plaque was cut into rings, and different type of atherosclerotic tissues, including media, fibrous cap (FC), lipid and intraplaque haemorrhage/thrombus (IPH/T) was dissected for uniaxial extension testing. In total, 65 media strips from 17 samples, 59 FC strips from 14 samples, 38 lipid strips from 11 samples, and 21 IPH/T strips from 11 samples were tested successfully. A modified Mooney–Rivlin strain energy density function was used to characterize the stretch–stress relationship. The stiffnesses of media and FC are comparable, as are lipid and IPH/T. However, both media and FC are stiffer than either lipid or IPH/T. The median values of incremental Young’s modulus of media, FC, lipid and IPH/T at λ = 1 are 290.1, 244.5, 104.4, 52.9, respectively; they increase to 1019.5, 817.4, 220.7 and 176.9 at λ = 1.1; and 4302.7, 3335.0, 533.4 and 268.8 at λ = 1.15 (unit, kPa; λ, stretch ratio). The material constants of each tissue type are suggested to be: media, c₁ = 0.138 kPa, D₁ = 3.833 kPa and D₂ = 18.803; FC, c₁ = 0.186 kPa, D₁ = 5.769 kPa and D₂ = 18.219; lipid, c₁ = 0.046 kPa, D₁ = 4.885 kPa and D₂ = 5.426; and IPH/T, c₁ = 0.212 kPa, D₁ = 4.260 kPa and D₂ = 5.312. It is concluded that all soft atherosclerotic tissues are non-linear, and both media and FC are stiffer than either lipid or IPH/T.