The Length of Hydrophobic Chain in Amphiphilic Polypeptides Regulates the Efficiency of Gene Delivery

Novel Hydrophilic Oligomer-Crosslinked Gelatin-Based Hydrogels for Biomedical Applications

Gelatin-based hydrogels have shown good injectability and biocompatibility and have been broadly used for drug delivery and tissue regeneration. However, their low mechanical strengths and fast degradation rates must be modified for long-term implantation applications. With an aim to develop mechanically stable hydrogels, reactive anhydride-based oligomers were developed and used to fabricate gelatin-based crosslinked hydrogels in this study. A cascade of hydrophilic oligomers containing reactive anhydride groups was synthesized by free radical polymerization. These oligomers varied in degree of reactivity, comonomer composition, and showed low molecular weights (M_n < 5 kDa). The reactive oligomers were utilized to fabricate hydrogels that differed in their mechanical strengths and degradation profiles. These formulations exhibited good cytocompatibility with human adipose tissue-derived stem cells (hADCs). In conclusion, the reactive MA-containing oligomers were successfully synthesized and utilized for the development of oligomer-crosslinked hydrogels. Such oligomer-crosslinked gelatin-based hydrogels hold promise as drug or cell carriers in various biomedical applications.

Amphiphilic Polypeptides Obtained by Post-Polymerization Modification of Poly-l-Lysine as Systems for Combined Delivery of Paclitaxel and siRNA

The development of effective anti-cancer therapeutics remains one of the current pharmaceutical challenges. The joint delivery of chemotherapeutic agents and biopharmaceuticals is a cutting-edge approach to creating therapeutic agents of enhanced efficacy. In this study, amphiphilic polypeptide delivery systems capable of loading both hydrophobic drug and small interfering RNA (siRNA) were developed. The synthesis of amphiphilic polypeptides included two steps: (i) synthesis of poly-αl-lysine by ring-opening polymerization and (ii) its post-polymerization modification with hydrophobic l-amino acid and l-arginine/l-histidine. The obtained polymers were used for the preparation of single and dual delivery systems of PTX and short double-stranded nucleic acid. The obtained double component systems were quite compact and had a hydrodynamic diameter in the range of 90-200 nm depending on the polypeptide. The release of PTX from the formulations was studied, and the release profiles were approximated using a number of mathematical dissolution models to establish the most probable release mechanism. A determination of the cytotoxicity in normal (HEK 293T) and cancer (HeLa and A549) cells revealed the higher toxicity of the polypeptide particles to cancer cells. The separate evaluation of the biological activity of PTX and anti-GFP siRNA formulations testified the inhibitory efficiency of PTX formulations based on all polypeptides (IC₅₀ 4.5-6.2 ng/mL), while gene silencing was effective only for the Tyr-Arg-containing polypeptide (56-70% GFP knockdown).

Lipopolyplex-Mediated Co-Delivery of Doxorubicin and FAK siRNA to Enhance Therapeutic Efficiency of Treating Colorectal Cancer

Tumor metastasis is a major concern in cancer therapy. In this context, focal adhesion kinase (FAK) gene overexpression, which mediates cancer cell migration and invasion, has been reported in several human tumors and is considered a potential therapeutic target. However, gene-based treatment has certain limitations, including a lack of stability and low transfection ability. In this study, a biocompatible lipopolyplex was synthesized to overcome the aforementioned limitations. First, polyplexes were prepared using poly(2-Hydroxypropyl methacrylamide-co-methylacrylate-hydrazone-pyridoxal) (P(HPMA-co-MA-hyd-VB6)) copolymers, which bore positive charges at low pH value owing to protonation of pyridoxal groups and facilitated electrostatic interactions with negatively charged FAK siRNA. These polyplexes were then encapsulated into methoxy polyethylene glycol (mPEG)-modified liposomes to form lipopolyplexes. Doxorubicin (DOX) was also loaded into lipopolyplexes for combination therapy with siRNA. Experimental results revealed that lipopolyplexes successfully released DOX at low pH to kill cancer cells and induced siRNA out of endosomes to inhibit the translation of FAK proteins. Furthermore, the efficient accumulation of lipopolyplexes in the tumors led to excellent cancer therapeutic efficacy. Overall, the synthesized lipopolyplex is a suitable nanocarrier for the co-delivery of chemotherapeutic agents and genes to treat cancers.

Random Copolymers of Lysine and Isoleucine for Efficient mRNA Delivery

Messenger RNA (mRNA) is currently of great interest as a new category of therapeutic agent, which could be used for prevention or treatment of various diseases. For this mRNA requires effective delivery systems that will protect it from degradation, as well as allow cellular uptake and mRNA release. Random poly(lysine-co-isoleucine) polypeptides were synthesized and investigated as possible carriers for mRNA delivery. The polypeptides obtained under lysine:isoleucine monomer ratio equal to 80/20 were shown to give polyplexes with smaller size, positive ζ-potential and more than 90% encapsulation efficacy. The phase inversion method was proposed as best way for encapsulation of mRNA into polyplexes, which are based on obtained amphiphilic copolymers. These copolymers showed efficacy in protection of bound mRNA towards ribonuclease and lower toxicity as compared to lysine homopolymer. The poly(lysine-co-isoleucine) polypeptides showed greater than poly(ethyleneimine) efficacy as vectors for transfection of cells with green fluorescent protein and firefly luciferase encoding mRNAs. This allows us to consider obtained copolymers as promising candidates for mRNA delivery applications.

Systematic Investigation of Biocompatible Cationic Polymeric Nucleic Acid Carriers for Immunotherapy of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third-largest cause of cancer death worldwide, while immunotherapy is rapidly being developed to fight HCC with great potential. Nucleic acid drugs are the most important modulators in HCC immunotherapy. To boost the efficacy of therapeutics and amplify the efficiency of genetic materials, biocompatible polymers are commonly used. However, under the strong need of a summary for current developments of biocompatible polymeric nucleic acid carriers for immunotherapy of HCC, there is rare review article specific to this topic to our best knowledge. In this article, we will discuss the current progress of immunotherapy for HCC, biocompatible cationic polymers (BCPs) as nucleic acid carriers used (or potential) to fight HCC, the roles of biocompatible polymeric carriers for nucleic acid delivery, and nucleic acid delivery by biocompatible polymers for immunotherapy. At the end, we will conclude the review and discuss future perspectives. This article discusses biocompatible polymeric nucleic acid carriers for immunotherapy of HCC from multidiscipline perspectives and provides a new insight in this domain. We believe this review will be interesting to polymer chemists, pharmacists, clinic doctors, and PhD students in related disciplines.

Poly(α-l-lysine)-based nanomaterials for versatile biomedical applications: Current advances and perspectives

Poly(α-l-lysine) (PLL) is a class of water-soluble, cationic biopolymer composed of α-l-lysine structural units. The previous decade witnessed tremendous progress in the synthesis and biomedical applications of PLL and its composites. PLL-based polymers and copolymers, till date, have been extensively explored in the contexts such as antibacterial agents, gene/drug/protein delivery systems, bio-sensing, bio-imaging, and tissue engineering. This review aims to summarize the recent advances in PLL-based nanomaterials in these biomedical fields over the last decade. The review first describes the synthesis of PLL and its derivatives, followed by the main text of their recent biomedical applications and translational studies. Finally, the challenges and perspectives of PLL-based nanomaterials in biomedical fields are addressed.

Controlled Block Polypeptide Composed of d-Type Amino Acids: A Therapeutics Delivery Platform to Inhibit Biofilm Formation of Drug-Resistant Bacteria

Antibiotic resistance of bacteria has been widely developed due to biofilm protection and separating the bacteria from antibiotics. The phenomenon of biofilm inhibition or disassembly by d-amino acids (DAAs) has been reported recently, while it was also challenged by some other scientists. Presuming DAAs work for biofilms on the surface of bacteria, delivery of the DAAs to disease sites is important while small DAAs are easily removed by kidney. To resolve the above issues, it is urgent to develop a biofilm inhibitor. To achieve this goal, we synthesized d-type polypeptides via NCA ring-opening polymerization with the initiator of HMDS to generate poly(CBZ-l-lysine)₃₃-block-poly(d-phenylalanine)₁₄. After deprotection, the resultant polypeptides were converted into amphiphilic poly(l-lysine)₃₃-block-poly(d-phenylalanine)₁₄, which can be self-assembled into well-defined homogeneous nanoparticles capable of capsulizing penicillin G. For the molecular weight of polypeptides resulting in various bioeffects, we prepared similar-sized polypeptides of an l-type equivalent polypeptide as control. The data from microbial experiments indicated that poly(l-lysine)₃₃-block-poly(d-phenylalanine)₁₄ can inhibit biofilm formation of Bacillus subtilis at a low final concentration (24 μg/mL), much stronger than poly(l-lysine)₄₀-block-poly(l-phenylalanine)₁₉ at the same concentration. This is the first report in that synthetic d-type polypeptides can inhibit biofilms of bacteria. Poly(l-lysine)₃₃-block-poly(d-phenylalanine)₁₄ can be assembled into well-defined, biostable homogeneous nanoparticles. This research provides a potential solution to overcome bacteria antibiotic resistance from small molecules to material sciences and gives a unique angle to understand the current dispute if DAAs can disassemble the biofilms. Additionally, these nanoparticles have great potential in the development of nanomedicines with a longer circulation time in blood and this discovery has implications in developing antimicrobial nanodevices for therapy and basic scientific interest.

Combination Chemotherapy of Lung Cancer - Co-Delivery of Docetaxel Prodrug and Cisplatin Using Aptamer-Decorated Lipid-Polymer Hybrid Nanoparticles

Purpose

Lung cancer is the leading cause of cancer mortality worldwide. Drug resistance is the major barrier for the treatment of non-small cell lung cancer (NSCLC). The aim of this research is to develop an aptamer-decorated hybrid nanoparticle for the co-delivery of docetaxel prodrug (DTXp) and cisplatin (DDP) and to treat lung cancer.

Materials and Methods

Aptamer-conjugated lipid–polymer ligands and redox-sensitive docetaxel prodrug were synthesized. DTXp and DDP were loaded into the lipid–polymer hybrid nanoparticles (LPHNs). The targeted efficiency of aptamer-decorated, DTXp and DDP co-encapsulated LPHNs (APT-DTXp/DDP-LPHNs) was determined by performing a cell uptake assay by flow cytometry-based analysis. In vivo biodistribution and anticancer efficiency of APT-DTXp/DDP-LPHNs were evaluated on NSCLC-bearing mice xenograft.

Results

APT-DTXp/DDP-LPHNs had a particle size of 213.5 ± 5.3 nm, with a zeta potential of 15.9 ± 1.9 mV. APT-DTXp/DDP-LPHNs exhibited a significantly enhanced cytotoxicity (drug concentration causing 50% inhibition was 0.71 ± 0.09 μg/mL), synergy antitumor effect (combination index was 0.62), and profound tumor inhibition ability (tumor inhibition ratio of 81.4%) compared with the non-aptamer-decorated LPHNs and single drug-loaded LPHNs.

Conclusion

Since the synergistic effect of the drugs was found in this system, it would have great potential to inhibit lung tumor cells and in vivo tumor growth.

Polyplexes of Functional PAMAM Dendrimer/Apoptin Gene Induce Apoptosis of Human Primary Glioma Cells In Vitro

Highly efficient and safe gene delivery has become an important aspect of neuronal gene therapy. We evaluated the ability of polyamidoamine (PAMAM) dendrimer grafted with phenylalanine, histidine, and arginine (PAMAM-FHR), a nonviral gene delivery vector, to deliver a therapeutic, tumor cell-specific killer gene, apoptin, into the human primary glioma cell line GBL-14 and human dermal fibroblasts. We performed a transfection assay using plasmids of luciferase and enhanced green fluorescent protein (EGFP) and assessed cell viability. Both cell lines were treated with complexes of PAMAM-FHR and apoptin after which their intracellular uptake and localization were examined by fluorescence-activated cell sorting (FACS)analysis and confocal laser scanning microscopy. Confocal microscopy showed that the PAMAM-FHR escaped from the endo-lysosome into the cytosol. Cell cycle phase distribution analysis, annexin V staining, and a tetramethylrhodamine ethyl ester (TMRE) assay established that apoptin triggered apoptosis in the GBL-14 cell line but not in normal fibroblasts. These results indicated that the PAMAM-FHR/apoptin complex is an effective gene vehicle for cancer therapy in vitro.

Novel Hydrophobic Associating Polymer with Good Salt Tolerance

A hydrophobic associating polymer named DiPHAM (acrylamide/sodium acrylamide-2-methylpropanesulfonic/sodium acrylate/N,N-di-n-dodecylacrylamide) with good salt tolerance was synthesized via photo-initiation polymerization. The critical association concentration (CAC) of DiPHAM was determined by viscosity changes to be 490 mg/L with different DiPHAM concentrations and particle sizes varied under such dynamic conditions. The influences of aqueous metal ions with different charges on its aqueous solution were investigated by measuring apparent viscosity, viscoelasticity, thixotropy, rheology, and particle size, and by SEM observation. The apparent viscosity of the DiPHAM solution was affected by metal ions to some extent, but the viscosity of the polymer can be still maintained at 55 mPa·s under 20 × 10⁴ mg/L NaCl. Divalent metal ions show greater impact on DiPHAM aqueous solutions, but the polymer solutions showed resistance to the changes caused in viscosity, structure, and viscoelasticity by Ca2+ and Mg2+ ions. The salt tolerance of DiPHAM is due to the combination of hydrophobic association, the electrostatic shield, and double layer compression of the hydration shell. Increasing the ion concentration enhances the dehydration and further compresses the hydration shell, making the non-structural viscosity decrease, even "salting out". Measurements of rheological properties showed that DiPHAM solutions could maintain a relatively high viscosity (0.6%-71 mPa·s/0.3%-50 mPa·s) after 120 min of continuous shearing (170 s-1) at 140 °C. Under high-salinity (5000 mg/L Ca2+/3000 mg/L Mg2+) conditions, the solution with 0.6 wt% DiPHAM still maintained a high viscosity (50 mPa·s/70 mPa·s) after continuously shearing for 120 min at 120 °C and 170 s-1. The good salt tolerance of DiPHAM can lead to a variety of applications, including in fracturing fluids for enhanced oil recovery (EOR) and in sewage treatment.