Synthesis and Properties of Low-Molecular-Weight PEI-Based Lipopolymers for Delivery of DNA

Tailoring the Degradation Time of Polycationic PEG-Based Hydrogels toward Dynamic Cell Culture Matrices

Poly(ethylene glycol)-based (PEG) hydrogels provide an ideal platform to obtain well-defined and tailor-made cell culture matrices to enhance in vitro cell culture conditions, although cell adhesion is often challenging when the cells are cultivated on the substrate surface. We herein demonstrate two approaches for the synthesis of polycationic PEG-based hydrogels which were modified to enhance cell-matrix interactions, to improve two-dimensional (2D) cell culture, and catalyze hydrolytic degradation. While the utilization of N,N-(bisacryloxyethyl) amine (BAA) as cross-linker for in situ gelation provides degradable scaffolds for dynamic cell culture, the incorporation of short segments of poly(N-(3-(dimethylamino)propyl)acrylamide) (PDMAPAam) provides high local cationic charge density leading to PEG-based hydrogels with high selectivity for fibroblastic cell lines. The adsorption of transforming growth factor (TGF-β) into the hydrogels induced stimulation of fibrosis and thus the formation of collagen as a natural ECM compound. With this, these dynamic hydrogels enhance in vitro cell culture by providing a well-defined, artificial, and degradable matrix that stimulates cells to produce their own natural scaffold within a defined time frame.

Revisiting of Properties and Modified Polyethylenimine-Based Cancer Gene Delivery Systems

A new era of medical technology in cancer treatment is a directly specific modification of gene expression in tumor cells by nucleic acid delivery. Currently, the main challenge to achieving this goal is to find a non-toxic, safe, and effective strategy for gene transfer to cancer cells. Synthetic composites based on cationic polymers have historically been favored in bioengineering due to their ability to mimic bimolecular structures. Among them, polyethylenimines (PEIs) with superior properties such as a wide range of molecular weight and a flexible structure may propel the development of functional combinations in the biomedical and biomaterial fields. Here, in this review, we will focus on the recent progressions in the formulation optimization of PEI-based polyplex in gene delivery to treat cancer. Also, the effect of PEI's intrinsic characteristics such as structure, molecular weight, and positive charges which influence the gene delivery efficiency will be discussed.

Alkylated Sulfonium Modification of Low Molecular Weight Polyethylenimine to Form Lipopolymers as Gene Vectors

Hydrophobic modification of low molecular weight polyethylenimine (PEI) is an efficient method to form ideal gene-transfer carriers. Sulfonium-a combination of three different functional groups, was conjugated onto PEI 1.8k at a conjugation ratio of 1:0.1 to form a series of sulfonium PEI (SPs). These SPs were hydrophobically modified and characterized by Fourier transform infrared and HNMR. DNA-condensing abilities of SPs were tested with gel retardation experiment, and their cytotoxicity was evaluated via the MTT assay. The particle size and zeta potential of SP/DNA nanoparticles were measured and evaluated for cellular uptake and transfection ability on HepG2 cell line. The results showed that the sulfonium moiety was attached to PEI 1.8k with a high yield at a conjugation ratio of 1:0.1. SPs containing longer alkyl chains condensed DNA completely at an SP/DNA weight ratio of 2:1. The formed nanoparticle size was in the range of 168-265 nm, and the zeta potential was +16-45 mV. The IC50 values of SPs were 6.5-43.2 μg/mL. The cytotoxicity of SPs increased as the hydrophobic chain got longer. SP/DNA showed much stronger cellular uptakes than PEI 25k; however, pure SPs presented almost no gene transfection on cells. Heparin release experiment showed that SP's strong binding of DNA resulted in low release of DNA and thus hindered the gene transfection process. By mixing SP with PEI 1.8k, the mixture presented adjustable DNA binding and releasing. The mixture formed by 67% SP and 33% PEI 1.8k showed strong gene transfection. In conclusion, sulfonium is an effective linkage to carry hydrophobic groups to adjust cell compatibilities and gene transfection capabilities of PEI.

Polymeric-Micelle-Based Delivery Systems for Nucleic Acids

Nucleic acids can modulate gene expression specifically. They are increasingly being utilized and show huge potential for the prevention or treatment of various diseases. However, the clinical translation of nucleic acids faces many challenges due to their rapid clearance after administration, low stability in physiological fluids and limited cellular uptake, which is associated with an inability to reach the intracellular target site and poor efficacy. For many years, tremendous efforts have been made to design appropriate delivery systems that enable the safe and effective delivery of nucleic acids at the target site to achieve high therapeutic outcomes. Among the different delivery platforms investigated, polymeric micelles have emerged as suitable delivery vehicles due to the versatility of their structures and the possibility to tailor their composition for overcoming extracellular and intracellular barriers, thus enhancing therapeutic efficacy. Many strategies, such as the addition of stimuli-sensitive groups or specific ligands, can be used to facilitate the delivery of various nucleic acids and improve targeting and accumulation at the site of action while protecting nucleic acids from degradation and promoting their cellular uptake. Furthermore, polymeric micelles can be used to deliver both chemotherapeutic drugs and nucleic acid therapeutics simultaneously to achieve synergistic combination treatment. This review focuses on the design approaches and current developments in polymeric micelles for the delivery of nucleic acids. The different preparation methods and characteristic features of polymeric micelles are covered. The current state of the art of polymeric micelles as carriers for nucleic acids is discussed while highlighting the delivery challenges of nucleic acids and how to overcome them and how to improve the safety and efficacy of nucleic acids after local or systemic administration.

Smart co-delivery of miR-34a and cytotoxic peptides (LTX-315 and melittin) by chitosan based polyelectrolyte nanocarriers for specific cancer cell death induction

A novel polyelectrolyte nanocarrier was synthesized via layer-by-layer self-assembly of polycationic and polyanionic chains. The nanocarrier is composed of polyglutamate grafted chitosan core, dextran sulfate as a complexing agent, and polyethyleneimine shell decorated with folic acid. This polyelectrolyte complex has unique physicochemical properties so that the core is considered as an efficient carrier for LTX-315 and melittin peptides, and the shell is suitable for delivery of miR-34a. The spherical nanocarriers with an average size of 123 ± 5 nm and a zeta potential of -36 ± 1 mV demonstrated controlled-release of gene and peptides ensured a synergistic effect in establishing multiple cell death pathways on chemoresistance human breast adenocarcinoma cell line, MDA-MB-231. In vitro cell viability assays also revealed no cytotoxicity for the nanocarriers, and an IC50 of 15 μg/mL and 150 μg/mL for melittin and LTX-315, respectively, after 48 h, whereas co-delivery of melittin with miR-34a increased smart death induction by 54%.

Synthesis and Characterization of Mannosylated Formulations to Deliver a Minicircle DNA Vaccine

DNA vaccines still represent an emergent area of research, giving rise to continuous progress towards several biomedicine demands. The formulation of delivery systems to specifically target mannose receptors, which are overexpressed on antigen presenting cells (APCs), is considered a suitable strategy to improve the DNA vaccine immunogenicity. The present study developed binary and ternary carriers, based on polyethylenimine (PEI), octa-arginine peptide (R8), and mannose ligands, to specifically deliver a minicircle DNA (mcDNA) vaccine to APCs. Systems were prepared at various nitrogen to phosphate group (N/P) ratios and characterized in terms of their morphology, size, surface charge, and complexation capacity. In vitro studies were conducted to assess the biocompatibility, cell internalization ability, and gene expression of formulated carriers. The high charge density and condensing capacity of both PEI and R8 enhance the interaction with the mcDNA, leading to the formation of smaller particles. The addition of PEI polymer to the R8-mannose/mcDNA binary system reduces the size and increases the zeta potential and system stability. Confocal microscopy studies confirmed intracellular localization of targeting systems, resulting in sustained mcDNA uptake. Furthermore, the efficiency of in vitro transfection can be influenced by the presence of R8-mannose, with great implications for gene expression. R8-mannose/PEI/mcDNA ternary systems can be considered valuable tools to instigate further research, aiming for advances in the DNA vaccine field.

Nanoparticle-Based Rifampicin Delivery System Development

The alkaline milieu of chronic wounds severely impairs the therapeutic effect of antibiotics, such as rifampicin; as such, the development of new drugs, or the smart delivery of existing drugs, is required. Herein, two innovative polyelectrolyte nanoparticles (PENs), composed of an amphiphilic chitosan core and a polycationic shell, were synthesized at alkaline pH, and in vitro performances were assessed by ¹H NMR, elemental analysis, FT-IR, XRD, DSC, DLS, SEM, TEM, UV/Vis spectrophotometry, and HPLC. According to the results, the nanostructures exhibited different morphologies but similar physicochemical properties and release profiles. It was also hypothesized that the simultaneous use of the nanosystem and an antioxidant could be therapeutically beneficial. Therefore, the simultaneous effects of ascorbic acid and PENs were evaluated on the release profile and degradation of rifampicin, in which the results confirmed their synergistic protective effect at pH 8.5, as opposed to pH 7.4. Overall, this study highlighted the benefits of nanoparticulate development in the presence of antioxidants, at alkaline pH, as an efficient approach for decreasing rifampicin degradation.

Silencing of Gasdermin D by siRNA-Loaded PEI-Chol Lipopolymers Potently Relieves Acute Gouty Arthritis through Inhibiting Pyroptosis

Gasdermin D (GSDMD) plays a causal role in NOD-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis eruption, which has been regarded as a potential therapeutic target for pyroptosis-related diseases including acute gouty arthritis. In the present study, the synthesized PEI-Chol (cholesterol grafted polyethylenimine) was assembled with GSDMD small interfering RNA (siRNA) to form PEI-Chol/siGSDMD polyplexes, which provided high transfection efficiency for siRNA-mediated GSDMD knockdown. Then we evaluated the effect of GSDMD siRNA-loaded PEI-Chol on inflammatory cascades in bone-marrow-derived macrophages (BMDMs) and acute gouty arthritis animal models under MSU exposure. When accompanied by pyroptosis blockade and decreased release of interleukin-1 beta (IL-1β), NLRP3 inflammasome activation was also suppressed by GSDMD knockdown in vivo and in vitro. Moreover, in MSU-induced acute gouty arthritis mice, blocking GSDMD with siRNA significantly improved ankle swelling and inflammatory infiltration observed in histopathological analysis. Furthermore, investigation using a mouse air pouch model verified the effect of siGSDMD-loaded PEI-Chol on pyroptosis of recruited macrophages and related signaling pathways in response to MSU. These novel findings exhibited that GSDMD knockdown relieved acute gouty arthritis through inhibiting pyroptosis, providing a possible therapeutic approach for MSU-induced acute gouty arthritis molecular therapy using PEI-Chol as a nucleic acid delivery carrier.

Polyplexes System to Enhance the LL-37 Antimicrobial Peptide Expression in Human Skin Cells

Inefficient autologous tissue recovery in diverse skin injuries increases the susceptibility of patients to infections caused by multiresistant microorganisms, resulting in a high mortality rate. Nonviral transfection is an attractive alternative for these patients, where genetically modified cells incorporated into skin substitutes could release additional antimicrobial agents into the native skin. In this work, we have modulated the conditions of using a nonviral system for transfection of primary human keratinocytes and fibroblasts, consisting of a polymer/plasmid DNA (pDNA) complex called polyplex and its effects on the expression of LL-37 antimicrobial peptide. Linear and branched polyethylenimine (PEI) polymers in different weight concentrations were varied for evaluating the formation and colloidal characteristics of the polyplexes. The PEI/pDNA polyplexes with 19 nitrogen/phosphate ratio are nanometric particles (400 and 250 nm with linear and branched PEI, respectively) exhibiting positive surface (+30 ± 2 mV). Both kinds of polyplexes allowed the expression of a reporter gene and increased the human cathelicidin antimicrobial peptide gene expression in transfected keratinocytes and fibroblasts; however, greater cytotoxicity was observed when polyplexes formed with branched PEI were used. Moreover, cell culture supernatants from transfected cells with linear PEI/pDNA polyplexes showed enhanced antimicrobial activity (decrease of bacterial growth in 95.8%) against a Staphylococcus aureus strain in vitro. The study of the PEI/pDNA polyplexes formation allowed us to develop an improved transfection strategy of skin cells, promoting the production of LL-37 antimicrobial peptide. In the future, this strategy could be used for the construction of skin substitutes to prevent, reduce, or eliminate bacterial infections. Impact statement The results of this study contribute to the understanding of the polyplexes system in the genetic modification of skin cells and its effects on the expression of the LL-37 antimicrobial peptide. In the future, three-dimensional skin substitutes built with these cells could be an efficient way to decrease bacterial growth and prevent the infections in skin wounds.