Free energy landscape of siRNA-polycation complexation: Elucidating the effect of molecular geometry, polymer flexibility, and charge neutralization

The success of medical threatments with DNA and silencing interference RNA is strongly related to the design of efficient delivery technologies. Cationic polymers represent an attractive strategy to serve as nucleic-acid carriers with the envisioned advantages of efficient complexation, low cost, ease of production, well-defined size, and low polydispersity index. However, the balance between efficacy and toxicity (safety) of these polymers is a challenge and in need of improvement. With the aim of designing more effective polycationic-based gene carriers, many parameters such as carrier morphology, size, molecular weight, surface chemistry, and flexibility/rigidity ratio need to be taken into consideration. In the present work, the binding mechanism of three cationic polymers (polyarginine, polylysine and polyethyleneimine) to a model siRNA target is computationally investigated at the atomistic level. In order to better understand the polycationic carrier-siRNA interactions, replica exchange molecular dynamic simulations were carried out to provide an exhaustive exploration of all the possible binding sites, taking fully into account the siRNA flexibility together with the presence of explicit solvent and ions. Moreover, well-tempered metadynamics simulations were employed to elucidate how molecular geometry, polycation flexibility, and charge neutralization affect the siRNA-polycations free energy landscape in term of low-energy binding modes and unbinding free energy barriers. Significant differences among polymer binding modes have been detected, revealing the advantageous binding properties of polyarginine and polylysine compared to polyethyleneimine

Medical and environmental application of chitosan

The goal of this research was to develop and characterize new formulations based on chitosan and its derivatives for industrial and medical applications. First, chitosan beads, cross-linked or not, were evaluated for removing heavy metals/azo-dyes from waste waters. Adsorption was characterized as a function of pH, adsorbent dosage, contact time and initial metal ion/azo-dyes concentration. Equilibrium data were fitted to different adsorption models and were best modeled by a pseudo-second order kinetic and a Langmuir isotherm (monolayer distribution). The beads can efficiently remove 99% of heavy metals/azo-dyes from aqueous solutions. Secondly, chitosan was functionalized with adhesion-promoting RGDC peptide to accelerate wound healing. In this view, three different formulations for topical application have been characterized and evaluated. Both derivatized chitosan and formulations showed no toxicity, induced adhesion and proliferation of human dermal fibroblasts. RGDC-functionalized chitosan provides an optimal environment for fibroblast adhesion and proliferation, supporting its potential to accelerate wound healing

An Update on Antimicrobial Peptides (AMPs) and Their Delivery Strategies for Wound Infections

Bacterial infections occur when wound healing fails to reach the final stage of healing, which is usually hindered by the presence of different pathogens. Different topical antimicrobial agents are used to inhibit bacterial growth due to antibiotic failure in reaching the infected site, which is accompanied very often by increased drug resistance and other side effects. In this review, we focus on antimicrobial peptides (AMPs), especially those with a high potential of efficacy against multidrug-resistant and biofilm-forming bacteria and fungi present in wound infections. Currently, different AMPs undergo preclinical and clinical phase to combat infection-related diseases.AMP dendrimers (AMPDs) have been mentioned as potent microbial agents. Various AMP delivery strategies that are used to combat infection and modulate the healing rate—such as polymers,scaffolds, films and wound dressings, and organic and inorganic nanoparticles—have been discussed as well. New technologies such as Clustered Regularly Interspaced Short Palindromic Repeat(CRISPR)-associated protein (CRISPR-Cas) are taken into consideration as potential future tools for AMP delivery in skin therapy

Comparison of triblock copolymeric micelles based on α- and ε-poly(L-lysine): a Cornelian choice

Abstract Due to the lack of safe carriers for the delivery of small interfering RNA (siRNA), clinical applications of nucleotide-based therapeutics have been limited. In this study, biodegradable amphiphilic triblock copolymers with tailored molecular weights for each block composed of methoxy poly(ethylene glycol) (2000 g/mol), poly( L -lysine) (1300 g/mol) and poly( D , L -lactic acid) (1800 g/mol) (mPEG 45 -α-PLL 10 -PLA 25 ) were synthesized and fully characterized. The peptide synthesis was carried out on a solid phase to limit the presence of cationic charges. The arrangement and availability of cationic amino groups within a micellar vector were investigated to determine the colloidal stability as well as the predisposition of these systems to vectorize siRNAs in addition to their already known ability to improve the solubility of hydrophobic compounds. For this purpose, a triblock copolymer containing an epsilon poly( L -lysine) was synthesized similarly. Accordingly, the arrangement of the cationic segment modifies the rigidity involving a complexation constraint due to limited cationic charges available on the surface, which can compromise the efficiency of delivery into cells. In addition, the two vectors were biocompatible in different human cell lines. </p

Comparison of triblock copolymeric micelles based on α- and ε-poly(L-lysine): a Cornelian choice

AbstractTriblock copolymer

Characterization of pDNA-TMC Nanoparticle Interaction and Stability

Formulation of nanoparticulate DNA vaccines requires the assessment of stability and integrity of the components implicated. Stability of cationic nanoparticles made of N-trimethyl chitosan and chondroitin sulfate (TMC nanoparticles) was investigated in aqueous solution and after freeze-drying by characterization of their size, polydispersity index (PDI), and zeta potential. Furthermore, the structural integrity of plasmid DNA (pDNA) on adsorption to the nanoparticle surface was investigated. Agarose gel electrophoresis showed DNA retention when applied with the nanocarrier, suggesting that pDNA adsorption on nanoparticles took place. In circular dichroism (CD) spectra, ellipticity of pDNA decreased at 280 nm and increased at 245 nm, and the maximum wavelength shifted from 275 nm to 285 nm when nanoparticles were present. Once released from the particles, the secondary structure of the plasmid was retained in its native form. pDNA release from pDNA-TMC nanoparticles was indicated by a rise in zeta potential from initially -32 mV (pDNA adsorbed to particles) to 14 mV during one hour, and to 36 mV after 24 hours. Unloaded TMC nanoparticles remained stable in suspension for 24 hours, maintaining diameters of around 200 nm, and zeta potential values of approximately 38 mV. Freeze-drying with sucrose could ensure storage for 30 days, with minimal increase in size (291 nm) and charge (62 mV). In conclusion, TMC nanoparticles may potentially be freeze-dried in the presence of sucrose to be stored for prolonged periods of time. Furthermore, pDNA was successfully adsorbed to the cationic nanoparticles and remained intact after being released

Cellular Interaction And Tumoral Penetration Properties Of Cyclodextrin Nanoparticles On 3D Breast Tumor Model

Amphiphilic cyclodextrins are biocompatible oligosaccharides that can be used for drug delivery especially for the delivery of drugs with solubility problems thanks to their unique molecular structures. In this paper, Paclitaxel was used as a model anticancer drug to determine the inclusion complex properties of amphiphilic cyclodextrins with different surface charge. Paclitaxel-loaded cyclodextrin nanoparticles were characterized in terms of mean particle diameter, zeta potential, encapsulation efficacy, drug release profile and cell culture studies. It was determined that the nanoparticles prepared from the inclusion complex according to characterization studies have a longer release profile than the conventionally prepared nanoparticles. In order to mimic the tumor microenvironment, breast cancer cells and healthy fibroblast cells were used in 3-dimensional (3D) cell culture studies. It was determined that the activities of nanoparticles prepared by conventional methods behave differently in 2-dimensional (2D) and 3D cell cultures. In addition, it was observed that the nanoparticles prepared from the inclusion complex have a stronger anti-tumoral activity in the 3D multicellular tumor model than the drug solution. Furthermore, polycationic amphiphilic cyclodextrin nanoparticles can diffuse and penetrate through multilayer cells in a 3D tumor model, which is crucial for an eventual antitumor effect.PubMedWoSScopu

Chitosan as a starting material for wound healing applications

Chitosan and its derivatives have attracted great attention due to their properties beneficial for application to wound healing. The main focus of the present review is to summarize studies involving chitosan and its derivatives, especially N,N,N-trimethyl-chitosan (TMC), N,O-carboxymethyl-chitosan (CMC) and O-carboxymethyl-N,N,N-trimethyl-chitosan (CMTMC), used to accelerate wound healing. Moreover, formulation strategies for chitosan and its derivatives, as well as their in vitro, in vivo and clinical applications in wound healing are described

Are Antimicrobial Peptide Dendrimers an Escape from ESKAPE?

Significance: The crisis of antimicrobial resistance (AMR) increases dramatically despite all efforts to use available antibiotics or last resort antimicrobial agents. The spread of the AMR, declared as one of the most important health-related issues, warrants the development of new antimicrobial strategies. Recent Advances: Antimicrobial peptides (AMPs) and AMP dendrimers (AMPDs), as well as polymer dendrimers are relatively new and promising strategies with the potential to overcome drug resistance issues arising in ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) colonizing chronic wounds. Critical Issues: AMPs-AMPDs suffer from limited efficacy, short-lasting bioactivity, and concerns of toxicity. To circumvent these drawbacks, their covalent coupling to biopolymers and/or encapsulation into different drug carrier systems is investigated, with a special focus on topical applications. Future Directions: Scientists and the pharmaceutical industry should focus on this challenging subject to either improve the activity of existing antimicrobial agents or find new drug candidates. The focus should be put on the discovery of new drugs or the combination of existing drugs for a better synergy, taking into account all kinds of wounds and existing pathogens, and more specifically on the development of next-generation antimicrobial peptides, encompassing the delivery carrier toward improved pharmacokinetics and efficacy