Gene therapy holds immense potential as a future therapeutic strategy for the treatment of numerous genetic diseases which are incurable to date. Nevertheless, safe and efficient gene delivery remains the most challenging aspects of gene therapy. To overcome this difficulty a series of hexanoic acid (HA) and monomethoxy poly(ethylene glycol) (mPEG) double grafted chitosan-based (HPC) nanomicelles were developed as nonviral gene carrier. HPC polymers with various HA and mPEG substitution degrees were synthesized, and their chemical structures were confirmed by (1)H NMR spectroscopy. HPC nanomicelles exhibited excellent blood compatibility and cell viability, as demonstrated by in vitro hemolysis and MTT assay, respectively. The cationic HPC nanomicelles retained the plasmid DNA (pDNA) binding capacity of chitosan and formed stable HPC/pDNA polyplexes with diameters below 200 nm. Both hydrophobic and hydrophilic substitution resulted in suppressed nonspecific protein adsorption on HPC/pDNA polyplexes and increased pDNA dissociation. However, resistance against DNase I degradation was enhanced by HA conjugation while being inhibited by mPEG substitution. Amphiphilic modification resulted in 3-4.5-fold higher cellular uptake in human embryonic kidney 293 cells (HEK 293) mainly through clathrin-mediated pathway. The optimal HPC/pDNA polyplexes displayed 50-fold and 1.2-fold higher gene transfection compared to unmodified chitosan and Fugene, respectively, in HEK 293 cells. Moreover, both the cellular uptake and in vitro transfection study suggested a clear dependence of gene expression on the extent of HA and mPEG substitution. These findings demonstrate that amphiphilic HPC nanomicelles with the proper combination of HA and mPEG substitution could be used as a promising gene carrier for efficient gene therapy.

Gene therapy is an emerging therapeutic strategy for the cure or treatment of a spectrum of genetic disorders. Nevertheless, advances in gene therapy are immensely reliant upon design of an efficient gene carrier that can deliver genetic cargoes into the desired cell populations. Among various nonviral gene delivery systems, chitosan-based carriers have gained increasing attention because of their high cationic charge density, excellent biocompatibility, nearly nonexistent cytotoxicity, negligible immune response, and ideal ability to undergo chemical conjugation. However, a major shortcoming of chitosan-based carriers is their poor cellular uptake, leading to inadequate transfection efficiency. The intrinsic feature of cell penetrating peptides (CPPs) for transporting diverse cargoes into multiple cell and tissue types in a safe manner suggests that they can be conjugated to chitosan for improving its transfection efficiency. In this review, we briefly discuss CPPs and their classification, and also the major mechanisms contributing to the cellular uptake of CPPs and cargo conjugates. We also discuss immense improvements for the delivery of nucleic acids using CPP-conjugated chitosan-based carriers with special emphasis on plasmid DNA and small interfering RNA.

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The purpose of this study was to investigate the effects of size and type of incorporated model molecules on the polymer degradation and release profile from thermosensitive triblock copolymer based controlled delivery systems. In vitro release of the incorporated molecules demonstrated slow release for risperidone (molecular weight (M w ) = 410.48 Da; partition coefficient (K o/w ) = 3.49), while bovine serum albumin (BSA) (M w = "66,400 Da; K o/w = 0.007) and insulin (M w = 5808 Da; K o/w = 0.02) showed initial burst release followed by controlled release. The proton NMR, Gel Permeation Chromatography, and Cryo-SEM studies suggest that the size and partition coefficient of incorporated molecules influence the pore size, polymer degradation, and their release. In spite of using a similar polymer delivery system the polymer degradation rate and drug release notably differ for these model molecules. Therefore, size and oil-water partition coefficient are important factors for designing the controlled release formulation of therapeutics from triblock copolymer based delivery systems.Polymers 2015, 7 1511

Osteoporosis is a common metabolic bone disorder associated with fragility and bone fracture. Worldwide, osteoporosis results in more than 8.9 million fractures annually. Additionally, steroid treatments can cause osteoporosis as a side effect. Salmon calcitonin (sCT) is injected daily for those on steroid treatments as a means to prevent and treat osteoporosis side effects. Frequent dosing is inconvenient, uncomfortable, and often leads to compliance issues. Our objective was to develop a monomethoxy poly(ethylene glycol) (mPEG) and poly-lactic-co-glycolic acid (PLGA) thermosensitive triblock copolymer (mPEG–PLGA–mPEG)-based controlled release delivery system at an increased lactide to glycolide ratio (3.5:1, 4.5:1, and 5:1) to deliver sCT in its active conformation in a controlled fashion for a prolonged period following a single subcutaneous injection. Increasing lactide to glycolide ratio increases hydrophobicity of the PLGA block, which slows degradation of copolymer, thereby prolonging release and reducing burst release. Proton nuclear magnetic resonance spectroscopy and gel permeation chromatography confirmed structural composition and polydispersity index, respectively. Critical micelle concentration of the copolymer was 25 μg/mL. The delivery system was biocompatible as determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell viability assay. Moreover, the copolymeric system maintained sCT in a conformationally stable form for the entire duration of storage and release.