Amino Acid-Modified Polyethylenimines with Enhanced Gene Delivery Efficiency and Biocompatibility

Polyethylenimine Inclusion to Develop Aqueous Alginate-Based Core-Shell Capsules for Biomedical Applications

Aqueous core-shell structures can serve as an efficient approach that allows cells to generate 3D spheroids with in vivo-like cell-to-cell contacts. Here, a novel strategy for fabricating liquid-core-shell capsules is proposed by inverse gelation of alginate (ALG) and layer-by-layer (LbL) coating. We hypothesized that the unique properties of polyethylenimine (PEI) could be utilized to overcome the low structural stability and the limited cell recognition motifs of ALG. In the next step, alginate dialdehyde (ADA) enabled the Schiff-base reaction with free amine groups of PEI to reduce its possible toxic effects. Scanning electron microscopy and light microscopy images proved the formation of spherical hollow capsules with outer diameters of 3.0 ± 0.1 mm for ALG, 3.2 ± 0.1 mm for ALG/PEI, and 4.0 ± 0.2 mm for ALG/PEI/ADA capsules. The effective modulus increased by 3-fold and 5-fold when comparing ALG/PEI/ADA and ALG/PEI to ALG capsules, respectively. Moreover, PEI-coated capsules showed potential antibacterial properties against both Staphylococcus aureus and Escherichia coli, with an apparent inhibition zone. The cell viability results showed that all capsules were cytocompatible (above 75.5%). Cells could proliferate and form spheroids when encapsulated within the ALG/PEI/ADA capsules. Monitoring the spheroid thickness over 5 days of incubation indicated an increasing trend from 39.50 μm after 1 day to 66.86 μm after 5 days. The proposed encapsulation protocol represents a new in vitro platform for developing 3D cell cultivation and can be adapted to fulfill the requirements of various biomedical applications.

Tuning the Potency of Farnesol-Modified Polyethylenimine with Polyanionic Trans-Booster to Enhance DNA Delivery

Low molecular weight polyethylenimine (PEI) based lipopolymers become an attractive strategy to construct nonviral therapeutic carriers with promising transfection efficiency and minimal toxicity. Herein, this paper presents the design and synthesis of novel farnesol (Far) conjugated PEI, namely PEI1.2k-SA-Far7. The polymers had quick DNA complexation, effective DNA unpacking (dissociation), and cellular uptake abilities when complexed with plasmid DNA. However, they were unable to provide robust transfection in culture, indicating inability of Far grafting to improve the transfection efficacy significantly. To overcome this limitation, the commercially available polyanionic Trans-Booster additive, which is capable of displaying electrostatic interaction with PEI1.2k-SA-Far7, has been used to enhance the uptake of pDNA polyplexes and transgene expression. pDNA condensation was successfully achieved in the presence of the Trans-Booster with more stable polyplexes, and in vitro transfection efficacy of the polyplexes was improved to be comparable to that obtained with an established reference reagent. The PEI1.2k-SA-Far7/pDNA/Trans-Booster ternary complex exhibited good compatibility with cells and minimal hemolysis activity. This work demonstrates the exemplary potency of using additives in polyplexes and the potential of resultant ternary complexes for effective pDNA delivery.

Conformational Changes of Poly(Maleic Anhydride-alt-styrene) Modified with Amino Acids in an Aqueous Medium and Their Effect on Cytocompatibility and Hemolytic Response

The conformational changes of poly(maleic anhydride-alt-styrene) (PSMA) modified with different amino acids (PSMA-Aa) were studied in an aqueous medium as a function of ionic strength and pH. The specific viscosity of PSMA-Aa decreased with increasing salt concentration due to a more compact conformation. There was a decrease in surface tension with increasing concentrations of the modified polyelectrolyte having a greater effect for the PSMA modified with l-phenylalanine at pH 7.0, demonstrating a greater surface-active character. The conformational changes were also confirmed by molecular dynamics studies, indicating that PSMA-Aa exhibits a compact structure at pH 4.0 and a more extended structure at pH 7.0. On the other hand, the conformational changes of PSMA-Aa were related to its biological response, where the higher surface-active character of the PSMA modified with l-phenylalanine correlates very well with the higher hemolytic activity observed in red blood cells, in which the surface-active capacity supports lytic potency in erythrocytes. The cytocompatibility assays indicated that there were no significant cytotoxic effects of the PSMA-Aa. Additionally, in solvent-accessible surface area studies, it was shown that the carboxylate groups of the PSMA modified with l-phenylalanine are more exposed to the solvent at pH 7.0 and high salt concentrations, which correlates with lower fluorescence intensity, reflecting a loss of mitochondrial membrane potential. It is concluded that the study of the conformational changes in PE modified with amino acids is essential for their use as biomaterials and relevant to understanding the possible effects of PE modified with amino acids in biological systems.

High Molecular Weight Poly(ethylenimine)-Based Water-Soluble Lipopolymer for Transfection of Cancer Cells

Over the past decade, search for novel materials for nucleic acid delivery has prompted a special interest in polymeric nanoparticles (NPs). In this study, the biological applicability of a water-soluble cationic lipopolymer (WSLP) obtained by the modification of high molecular weight branched poly(ethylenimine) (PEI) with cholesteryl chloroformate is characterized and assessed for better cellular membrane permeability. To test the delivery efficiency of the produced lipopolymer, plasmid DNA (pDNA) encoding the enhanced green fluorescent protein and WSLP are mixed at different charge ratios. WSLP and WSLP/pDNA complexes are characterized by dynamic and static light scattering, particle charge detection, scanning electron microscopy, and transmission electron microscopy. The pDNA loading of WSLP is also verified by agarose gel electrophoresis. Cytotoxicity of PEI, WSLP, and of WSLP/pDNA is evaluated on human A549 and HeLa cells. A remarkable dependence of the toxicity on the dose, cholesterylation, and charge ratio is detected. Transfection is monitored by flow cytometry and by fluorescence microscopy. Importantly, cholesterylation decreases the toxicity of the polymer, while promoting high transfection efficiency in both cell lines. This work indicates a possible optimization mode of the high molecular weight PEI-based WSLP rendering it a promising candidate for gene delivery.

Glutathione modified low molecular weight PEI for highly improved gene transfection ability and biocompatibility

A versatile oligopeptide, glutathione, was introduced to construct novel cationic gene vectors with further excellent transfection efficiency and serum tolerance.

Finding the ideal polyethylenimine-plasmid DNA system for co-delivery of payloads in cancer therapy

Researchers still hold for the development of a safety and advanced delivery system able of efficient therapeutic action. The co-delivery of different payloads is part of this strategy and has already demonstrated to be a valuable tool against the most severe diseases. In the pursuit of an "ideal" drug/gene co-delivery vector for cancer therapy, we present a complete comparison study of different morphology and molecular weight polyethylenimine (PEI)/p53 encoding plasmid DNA (pDNA) polyplexes. Besides pDNA, also methotrexate (MTX) has been loaded into PEI/pDNA nanoparticles. The polyplexes have been characterized in terms of morphology, size, surface charges, loading/encapsulation efficiencies and toxicity. Although the nature of PEI can influence these properties, they deeply vary with the polymer nitrogen to pDNA phosphate (N/P) ratio. The transfection of HeLa cells mediated by PEI/pDNA/MTX vectors leads to both the release of MTX and the p53 protein expression. Modelling of MTX release kinetics brings valuable information concerning drug delivery mechanism. Moreover, the success of transfection is dependent on the nature of PEI and, mainly, on the N/P ratio used in the formulation of polyplexes. This work represents a great contribution for the design and development of innovative PEI based carriers for the most challenging biomedical applications.

Current and future technological advances in transdermal gene delivery

Transdermal gene delivery holds significant advantages as it is able to minimize the problems of systemic administration such as enzymatic degradation, systemic toxicity, and poor delivery to target tissues. This technology has the potential to transform the treatment and prevention of a range of diseases. However, the skin poses a great barrier for gene delivery because of the "bricks-and-mortar" structure of the stratum corneum and the tight junctions between keratinocytes in the epidermis. This review systematically summarizes the typical physical and chemical approaches to overcome these barriers and facilitate gene delivery via skin for applications in vaccination, wound healing, skin cancers and skin diseases. Next, the advantages and disadvantages of different approaches are discussed and the insights for future development are provided.

Aromatic Modification of Low Molecular Weight PEI for Enhanced Gene Delivery

Low molecular weight polyethylenimine (1800 Da, also referred to as oligoethylenimines, OEI) was modified with amino acids, including two aromatic amino acids (tryptophan, phenylalanine) and an aliphatic amino acid (leucine). The substitution degree of amino acids could be controlled by adjusting the feeding mole ratio of the reactants. Fluorescence spectroscopy and circular dichroism experiments demonstrated that the indole ring of tryptophan may intercalate into the DNA base pairs and contribute to efficient DNA condensation. In vitro gene expression results revealed that the modified OEIs (OEI-AAs) may provide higher transfection efficiency even than high molecular weight polyethylenimine (25 kDa, PEI), especially the aromatic tryptophan substituted OEI. Moreover, OEI-AAs exhibited excellent serum tolerance, and up to 137 times higher transfection efficiency than PEI 25 kDa that was obtained in the presence of serum. The cytotoxicity of OEI-AAs is much lower than PEI 25 kDa. This study may afford a new method for the development of low molecular weight oligomeric non-viral gene vectors with both high efficiency and biocompatibility.

Engineered Hydrogels for Local and Sustained Delivery of RNA-Interference Therapies

It has been nearly two decades since RNA-interference (RNAi) was first reported. While there are no approved clinical uses, several phase II and III clinical trials suggest the great promise of RNAi therapeutics. One challenge for RNAi therapies is the controlled localization and sustained presentation to target tissues, to both overcome systemic toxicity concerns and to enhance in vivo efficacy. One approach that is emerging to address these limitations is the entrapment of RNAi molecules within hydrogels for local and sustained release. In these systems, nucleic acids are either delivered as siRNA conjugates or within nanoparticles. A plethora of hydrogels has been implemented using these approaches, including both traditional hydrogels that have already been developed for other applications and new hydrogels developed specifically for RNAi delivery. These hydrogels have been applied to various applications in vivo, including cancer, bone regeneration, inflammation and cardiac repair. This review will examine the design and implementation of such hydrogel RNAi systems and will cover the most recent applications of these systems.

Peptides, polypeptides and peptide–polymer hybrids as nucleic acid carriers

Peptide, polypeptide and polymer–peptide hybrid based nucleic acid therapeutics (NAT).