Synthesis and characterization of functionalized poly(γ-benzyl-l-glutamate) derivates and corresponding nanoparticles preparation and characterization

Improving aqueous solubility of paclitaxel with polysarcosine-b-poly(γ-benzyl glutamate) nanoparticles

New stealth amphiphilic copolymers based on polysarcosine (PSar) rather than poly(ethylene glycol) (PEG) have gained more attention for their use as excipients in nanomedicine. In this study, several polysarcosine-b-poly(γ-benzyl glutamate) (PSar-b-PGluOBn) block copolymers were synthesized by ring opening polymerization (ROP) of the respective N-carboxyanhydrides (NCAs) and were characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR) and size-exclusion chromatography (SEC). Copolymers had different PGluOBn block configuration (racemic L/D, pure L or pure D), degrees of polymerization of PSar between 28 and 76 and PGluOBn between 9 and 93, molar masses (M_n) between 5.0 and 24.6 kg.mol^-1 and dispersities (Đ) lower than 1.4. Nanoparticles of PSar-b-PGluOBn loaded with paclitaxel (PTX), a hydrophobic anti-cancer drug, were obtained by nanoprecipitation. Their hydrodynamic diameter (D_h) ranged from 27 to 118 nm with polydispersity indexes (PDI) between 0.01 and 0.20, as determined by dynamic light scattering (DLS). Their morphology was more spherical for copolymers with a racemic L/D PGluOBn block configuration synthesized at 5 °C. PTX loading efficiency was between 63 and 92 % and loading contents between 7 and 15 %. Using PSar-b-PGluOBn copolymers as excipients, PTX apparent water-solubility was significantly improved by a factor up to 6600 to 660 µg.mL^-1.

In Vitro Release Test of Nano-drug Delivery Systems Based on Analytical and Technological Perspectives

Background:

Nanotech products are gaining more attention depending on their advantages for improving drug solubility, maintenance of drug targeting, and attenuation of drug toxicity. In vitro release test is the critical physical parameter to determine the pharmaceutical quality of the product, to monitor formulation design and batch-to-batch variation.

Methods:

Spectrophotometric and chromatographic methods are mostly used in quantification studies from in vitro release test of nano-drug delivery systems. These techniques have advantages and disadvantages with respect to each other considering dynamic range, selectivity, automation, compatibility with in vitro release media and cost per sample.

Results:

It is very important to determine the correct kinetic profile of active pharmaceutical substances. At this point, the analytical method used for in vitro release tests has become a very critical parameter to correctly assess the profiles. In this review, we provided an overview of analytical methods applied to the in vitro release assay of various nanopharmaceuticals.

Conclusion:

This review presents practical direction on analytical method selection for in vitro release test on nanopharmaceuticals. Moreover, precautions on analytical method selection, optimization and validation were discussed.

Chitosan-myristate nanogel as an artificial chaperone protects neuroserpin from misfolding

Background:

Molecular chaperon-like activity for protein refolding was studied using nanogel chitosan-myristic acid (CMA) and the protein neuroserpin (NS), a member of the serine proteinase inhibitor superfamily (serpin).

Materials and Methods:

Recombinant his-tag fusion NS was expressed in Escherichia coli. For confirmation of refolding of the purified NS, structural analysis was performed by circular dichroism and spectrofluorometric along with its inhibitory activity, which was assayed by single-chain tissue plasminogen activator. For evaluating NS aggregation during preparation, the samples were separated on a 7.5% (w/v) nondenaturing polyacrylamide gel electrophoresis. MA and chitosan covalently join together by the formation of amide linkages through the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-mediated reaction. The morphology and size of the prepared CM nanogel were characterized by transmission electron microscopy and scanning electron microscopy.

Results:

Heating at different temperatures (25°C, 37°C, 45°C, 65°C, 80°C) results in a further rise in β-structures accompanied by a fall of helices and no significant change in random coils. Structural changes in NS in the presence of CMA nanogel were less than that in the absence of CMA nanogel. Mater nanogel effectively prevented aggregation of NS during temperature induced protein refolding by the addition of cyclodextrins. The nanogel activity resembled the host-guest chaperon activity.

Conclusion:

These conditions, called conformational disorders, include Alzheimer's, Parkinson's, Huntington's disease, the transmissible spongiform encephalopathies, prion diseases, and dementia. Nanogels can be useful in recovery of the structural normality of proteins in these diseases.

Novel injectable porous poly(γ-benzyl-l-glutamate) microspheres for cartilage tissue engineering: preparation and evaluation

A novel injectable synthetic polypeptide of a poly(γ-benzyl-l-glutamate) macroporous microcarrier was developed for cartilage tissue engineering.

Poly(γ-benzyl-L-glutamate)-PEG-alendronate multivalent nanoparticles for bone targeting

Hydroxyapatite (HAP), a highly specific component of bone tissue, is the main target in order to impart osteotropicity. Bone targeted nanoparticles can increase the strength of the interaction with HAP through multivalency and thus constitute a valuable strategy in the therapeutics of skeletal diseases. PBLG10k-b-PEG6k-alendronate nanoparticles (~ 75 nm) were prepared by a simple nanoprecipitation method. The calcium affinity (KCa(+2)=1.8 × 10(4)M(-1)) of these nanoparticles was evaluated using isothermal titration calorimetry. The multivalent interaction with HAP surfaces (KHAP) was studied by fluorescence and was estimated to be 1.1 × 10(10)M(-1), which is more than 4000 times stronger than the reported monovalent interaction between alendronate and HAP surfaces. Molecular modeling suggests that the number of binding sites available at the HAP surface is in large excess than what is required for the whole surface coverage by alendronate decorated nanoparticles. The lower calcium affinity of these nanoparticles than for HAP allows calcium bound nanoparticles to interact with HAP, which yields a deeper understanding of bone targeted carriers and could potentially improve their bone targeting properties.

Polymeric micelles based on poly(ethylene glycol) block poly(racemic amino acids) hybrid polypeptides: conformation-facilitated drug-loading behavior and potential application as effective anticancer drug carriers

In this work, racemic hybrid polypeptides poly(ethylene glycol) (PEG)-b-poly(racemic-leucine) (PRL) copolymers with different leucine residues have been synthesized and characterized. Using docetaxel as a model molecule, the high drug-loaded spherical micelles based on PEG-PRL were prepared successfully using dialysis, with a tunable particle size from 170 nm to 250 nm obtained by changing the length of the hydrophobic blocks. Facilitated drug-loading behavior (higher drug-loading ability and easier drug-loading process) of PEG-PRL compared with their corresponding levo forms (PEG-b-poly[levo leucine]) was observed and clarified for the first time. With this facilitation, the highest drug-loading content and efficiency of PEG-PRL micelles can achieve 11.2% ± 0.4% and 67.2% ± 2.4%, respectively. All drug-loaded PEG-PRL micelles exhibit a similar release behavior with a sustained release up to 72 hours. The PEG-PRL was shown to be nontoxic against MCF-7 and human umbilical vein endothelial cells up to a concentration of 100 μg/mL, displaying a good biocompatibility. Also, the docetaxel-loaded PEG-PRL micelles were more toxic than the free drug against MCF-7 human breast cancer cells – both dose and time dependent. Therefore, these high docetaxel-loaded micelles based on racemic hybrid polypeptides appear to be a novel promising nanomedicine for anticancer therapy.

Precipitation of nanohydroxyapatite on PLLA/PBLG/Collagen nanofibrous structures for the differentiation of adipose derived stem cells to osteogenic lineage

Tissue engineering and nanotechnology have enabled engineering of nanostructured materials to meet the current challenges in bone treatment owing to rising occurrence of bone diseases, accidental damages and defects. Poly(L-lactic acid)/Poly-benzyl-L-glutamate/Collagen (PLLA/PBLG/Col) scaffolds were fabricated by electrospinning and nanohydroxyapatite (n-HA) was deposited by calcium-phosphate dipping method for bone tissue engineering (BTE). The abundance and accessibility of adipose derived stem cells (ADSC) may prove to be novel cell therapeutics for bone repair and regeneration. ADSCs were cultured on these scaffolds and were induced to undergo osteogenic differentiation in the presence of PBLG/n-HA for BTE. The cell-biomaterial interactions were analyzed using cell proliferation, SEM and CMFDA dye extraction techniques. Osteogenic differentiation of ADSC was confirmed using alkaline phosphatase activity (ALP), mineralization (ARS) and dual immunofluorescent staining using both ADSC marker protein and Osteocalcin, which is a bone specific protein. The utmost significance of this study is the bioactive PBLG/n-HA biomolecule introduced on the polymeric nanofibers to regulate and improve specific biological functions like adhesion, proliferation and differentiation of ADSC into osteogenic lineage. This was evident from the immunostaining and CMFDA images of ADSCs showing cuboidal morphology, characteristic of osteogenic lineage. The observed results proved that the PLLA/PBLG/Col/n-HA scaffolds promoted greater osteogenic differentiation of ADSC as evident from the enzyme activity and mineralization profiles for bone tissue engineering.

Synthesis and characterization of surface-modified PBLG nanoparticles for bone targeting: in vitro and in vivo evaluations

In this study, poly(γ-benzyl-l-glutamate) (PBLG) polypeptide derivatives were synthesized by ring-opening polymerization of amino acid N-carboxyanhydride using selected amine-terminated initiators. Alendronate, a targeting moiety that has a strong affinity for bone, was conjugated to PBLG. Monomethoxy polyethylene glycol (PEG) was used for a hydrophilic layer on the surface of the nanoparticles (NPs) to avoid reticuloendothelial system uptake. NPs were prepared by nanoprecipitation technique not only for PBLG or PBLG-PEG but also for composite polymers with different ratios. Fluorescein isothiocyanate would be attached to the NPs as a labeling agent. The size and morphology of NPs were evaluated by dynamic laser light scattering and transmission electron microscopy, and were found to be in a useful range (less than 80 nm) for bone-targeted drug delivery. In addition, the PEGylation of NPs was supported by isothermal titration calorimetry analysis. The bone-targeting potential of NPs was evaluated in vitro by calcium binding and hydroxyapatite affinity assays, and in vivo by fluorescent imaging experiments on rats. The targeted NPs showed bright fluorescent labeling in femur tissue. These results demonstrated the possibility of optimized NPs prepared with new PBLG derivatives to accumulate in bone successfully.

Glycyrrhetinic acid-functionalized degradable micelles as liver-targeted drug carrier

Recently, many efforts have been devoted to investigating the application of functionalized micelles as targeted drug delivery carriers. In this study, glycyrrhetinic acid (GA, a liver targeting ligand) modified poly(ethylene glycol)-b-poly(γ-benzyl L-glutamate) micelles were prepared and evaluated as a potential liver-targeted drug carrier. The aggregation behavior, stability, size and morphology of the micelles were investigated. Anticancer drug doxorubicin (DOX) was encapsulated in the micelles. The drug release profile, in vivo distribution and the cytotoxicity against hepatic carcinoma QGY-7703 cells of DOX-loaded micelles were studied. The results indicated that the release profile was pH-dependent with Fickian diffusion kinetics. The micelles were remarkably targeted to the liver, inducing a 4.9-fold higher DOX concentration than that for free DOX · HCl. The DOX-loaded micelles exhibited almost twofold more potent cytotoxicity compared with DOX · HCl, and the cytotoxicity was time- and dosage-dependent. These results suggest that GA-functionalized micelles represent a promising carrier for drug delivery to the liver.

Pegylation of poly(γ-benzyl-L-glutamate) nanoparticles is efficient for avoiding mononuclear phagocyte system capture in rats

Poly(γ-benzyl-L-glutamate) (PBLG) derivatives are synthetic polypeptides for preparing nanoparticles with well controlled surface properties. The aim of this paper was to investigate the biodistribution of pegylated PBLG in rats. For this purpose, nanoparticles were prepared by a nanoprecipitation method using mixtures of different PBLG derivates, including a pegylated derivate to avoid mononuclear phagocyte system uptake. The morphology, size distribution, and surface charge of the nanoparticles were investigated as a function of the amount of polymer employed for the preparation. Moderately polydispersed nanoparticles (polydispersity index less than 0.2) were obtained. Their size increased with polymer concentration. The zeta potential values were negative whatever the formulations. The availability of polyethylene glycol chains on the nanoparticles’ surface was confirmed by measuring the decrease in bovine serum albumin adsorption. For in vivo distribution studies, pegylated and nonpegylated nanoparticles were prepared with polymer mixtures containing PBLG-fluorescein isothiocyanate and imaged by fluorescence microscopy to measure their accumulation in liver and spleen tissues of rats after intravenous administration. Injection of stealth formulations resulted in negligible fluorescence in liver and spleen compared with nonpegylated formulations, which suggests that these nanoparticles are promising candidates as a stealth-type long-circulating drug carrier system and could be useful for active targeting of drugs while reducing systemic side effects.