Filamentous condensation of DNA induced by pegylated poly-L-lysine and transfection efficiency

Emerging non-viral vectors for gene delivery

Gene therapy holds great promise for treating a multitude of inherited and acquired diseases by delivering functional genes, comprising DNA or RNA, into targeted cells or tissues to elicit manipulation of gene expression. However, the clinical implementation of gene therapy remains substantially impeded by the lack of safe and efficient gene delivery vehicles. This review comprehensively outlines the novel fastest-growing and efficient non-viral gene delivery vectors, which include liposomes and lipid nanoparticles (LNPs), highly branched poly(β-amino ester) (HPAE), single-chain cyclic polymer (SCKP), poly(amidoamine) (PAMAM) dendrimers, and polyethyleneimine (PEI). Particularly, we discuss the research progress, potential development directions, and remaining challenges. Additionally, we provide a comprehensive overview of the currently approved non-viral gene therapeutics, as well as ongoing clinical trials. With advances in biomedicine, molecular biology, materials science, non-viral gene vectors play an ever-expanding and noteworthy role in clinical gene therapy.

Biomaterial-based gene therapy

Gene therapy, a medical approach that involves the correction or replacement of defective and abnormal genes, plays an essential role in the treatment of complex and refractory diseases, such as hereditary diseases, cancer, and rheumatic immune diseases. Nucleic acids alone do not easily enter the target cells due to their easy degradation in vivo and the structure of the target cell membranes. The introduction of genes into biological cells is often dependent on gene delivery vectors, such as adenoviral vectors, which are commonly used in gene therapy. However, traditional viral vectors have strong immunogenicity while also presenting a potential infection risk. Recently, biomaterials have attracted attention for use as efficient gene delivery vehicles, because they can avoid the drawbacks associated with viral vectors. Biomaterials can improve the biological stability of nucleic acids and the efficiency of intracellular gene delivery. This review is focused on biomaterial-based delivery systems in gene therapy and disease treatment. Herein, we review the recent developments and modalities of gene therapy. Additionally, we discuss nucleic acid delivery strategies, with a focus on biomaterial-based gene delivery systems. Furthermore, the current applications of biomaterial-based gene therapy are summarized.

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.

Secondary structure of end group functionalized oligomeric-l-lysines: investigations of solvent and structure dependent helicity

Fibrillation of supramolecular building blocks represents an important model system for complex proteins and peptides, such as amyloidogenic proteins, displaying aggregation and subsequent collapse of their biological functions. In this work, we synthesized narrow-dispersed, end group-telechelic, oligomeric-(l-lysine(carboxybenzyl (Z)/trifluoroacetyl (TFA))) n s (n = 3-33) as a model system for studying assembly and secondary structure formation, prepared via ring opening polymerization (ROP) of N-carboxyanhydrides (NCA). Our primary goal was to understand the influence of amino acid chain length and end group-modification on the secondary structure and fibrillation of the oligo-Z/TFA-protected lysines. Synthesis was accomplished by initiation of ROP with 11-amino-undecene, followed by complete chain end functionalization reactions of the N-terminus by 10-undecenoyl-chloride. The so obtained oligomeric-(l-lysine(Z/TFA)) n s were fractionated according to their number of repeating units (n) with preparative GPC using DMF as the eluent. As proven by MALDI-ToF MS, 1H-NMR-spectroscopy and analytical GPC, they were separated into fractions with low polydispersity (Đ) values, ranging from 1.02-1.08. Secondary structural investigations of these narrowly-dispersed oligomeric-(l-lysine(Z/TFA)) n s (n = 33 ± 6, n = 18 ± 6, n = 12 ± 4, n = 5 ± 2) were accomplished by CD spectroscopy in TFE and HFIP, indicating that TFE was able to induce/stabilize the formation of α-helicity. Fibril formation of oligomeric-(l-lysine(Z/TFA)) n s with shorter chain lengths (n = 7 and n = 3) were chosen to investigate the effect of the number of repeating units' role on the self-assembly of the oligomers in TFE. TEM images of these selected fractions, f19 with n = 7 and f28 with n = 3, showed that fibrillization occured and the formation of a dense fibrillar mesh was observed when the amino acid chain length is equal to 7. Therefore, the influences of the number of repeating units (n), end-group functionalities (mono- or bis-functional) and the choice of solvents (TFE or HFIP) on the propensity to form helical structure allowed us to calibrate their secondary structure.

New insight into formation of DNA-containing microparticles during PCR: the scaffolding role of magnesium pyrophosphate crystals

This work aims to study molecular mechanisms involved in the formation of DNA-containing microparticles and nanoparticles during PCR. Both pyrophosphate and Mg(2+) ions proved to play an important role in the generation of DNA microparticles (MPs) with a unique and sophisticated structure in PCR with Taq polymerase. Thus, the addition of Tli thermostable pyrophosphatase to a PCR mixture inhibited this process and caused the destruction of synthesized DNA MPs. Thermal cycling of Na-pyrophosphate (Na-PPi)- and Mg(2+)-containing mixtures (without DNA polymerase and dNTPs) under the standard PCR regime yielded crystalline oval or lenticular microdisks and 3D MPs composed from magnesium pyrophosphate (Mg-PPi). As shown by scanning electron microscopy (SEM), the produced Mg-PPi microparticles consisted of intersecting disks or their segments. They were morphologically similar but simpler than DNA-containing MPs generated in PCR. The incorporation of dNTPs, primers, or dsDNA into Mg-pyrophosphate particles resulted in the structural diversification of 3D microparticles. Thus, the unusual and complex structure of DNA MPs generated in PCR is governed by the unique feature of Mg-pyrophosphate to form supramolecular particles during thermal cycling. We hypothesize the Mg-pyrophosphate particles that are produced during thermal cycling serve as scaffolds for amplicon DNA condensation.

Addition of poly (propylene glycol) to multiblock copolymer to optimize siRNA delivery

Previous studies have examined different strategies for siRNA delivery with varying degrees of success. These include use of viral vectors, cationic liposomes, and polymers. Several copolymers were designed and synthesized based on blocks of poly(ethylene glycol) PEG, poly(propylene glycol) PPG, and poly(l-lysine). These were designated as P1, P2, and P3. We studied the copolymer self-assembly, siRNA binding, particle size, surface potential, architecture of the complexes, and siRNA delivery. Silencing of GFP using copolymer P3 to deliver GFP-specific siRNA to Neuro-2a cells expressing GFP was almost as effective as using Lipofectamine 2000, with minimal cytotoxicity. Thus, we have provided a new copolymer platform for siRNA delivery that we can continue to modify for improved delivery of siRNA in vitro and eventually in vivo.

Role of DNA in condensation and combinative self-assembly

We reveal the vital role of DNA topology and conformation in directing the combinative self-assembly and condensation pathway and morphology.

Isothermal microcalorimetry to investigate non specific interactions in biophysical chemistry

Isothermal titration microcalorimetry (ITC) is mostly used to investigate the thermodynamics of “specific” host-guest interactions in biology as well as in supramolecular chemistry. The aim of this review is to demonstrate that ITC can also provide useful information about non-specific interactions, like electrostatic or hydrophobic interactions. More attention will be given in the use of ITC to investigate polyelectrolyte-polyelectrolyte (in particular DNA-polycation), polyelectrolyte-protein as well as protein-lipid interactions. We will emphasize that in most cases these “non specific” interactions, as their definition will indicate, are favoured or even driven by an increase in the entropy of the system. The origin of this entropy increase will be discussed for some particular systems. We will also show that in many cases entropy-enthalpy compensation phenomena occur.