Development and evaluation of RADA-PDGF2 self-assembling peptide hydrogel for enhanced skin wound healing.

Background: Wound healing complications affect numerous patients each year, creating significant economic and medical challenges. Currently, available methods are not fully effective in the treatment of chronic or complicated wounds; thus, new methods are constantly sought. Our previous studies showed that a peptide designated as PDGF2 derived from PDGF-BB could be a promising drug candidate for wound treatment and that RADA16-I can serve as a release system for bioactive peptides in wound healing. Based on that, in this work, we designed a new self-assembling hydrogel RADA-PDGF2, connecting both peptides by a sequence specific for neutrophil elastase, and evaluated its activity in wound healing. Methods: The physicochemical properties of the designed scaffold were analyzed using transmission electron microscopy, atomic force microscopy, cryoSEM microscopies, and circular dichroism spectroscopy. The enzymatic cleavage was performed using human neutrophil elastase and monitored using high-performance liquid chromatography and MS spectroscopic techniques. The aforementioned techniques (HPLC and MS) were also used to assess the stability of the peptide in water and human plasma. The biological activity was analyzed on human skin cells using a colorimetric XTT test, collagen synthesis evaluation, and a migration assay. The biocompatibility was analyzed with LDH cytotoxicity assay and flow cytometric analysis of activation of immune cells. Finally, RADA-PDGF2 activity in wound healing was checked in a mouse dorsal skin injury model. Results: The analysis showed that RADA-PDGF2 can self-assemble, form a hydrogel, and release a bioactive sequence when incubated with human elastase. It shows pro-proliferative and pro-migratory properties and accelerates wound closure in the mouse model compared to RADA16-I. In addition, it is not cytotoxic to human cells and does not show immunogenicity. RADA-PDGF2 seems to be a promising drug candidate for wound management.

Immunomodulatory properties of new conjugates of muramyl dipeptide and nor-muramyl dipeptide with retro-tuftsin (Arg-Pro-Lys-Thr-OMe).

Six new conjugates of muramyl dipeptide and nor-muramyl dipeptide with retro-tuftsin were synthesised at Gdansk University of Technology. All compounds were investigated at Medical University of Gdansk. Their immunomodulatory properties were assessed using in vitro cultures of human subpopulations of white blood cells (peripheral blood mononuclear cells, peripheral blood lymphocytes, monocytes). We examined the viability of blood cells incubated with examined conjugates, as well as their ability to stimulate secretion of cytokines (TNFalpha--tumour necrosis factor alpha, IL6--interleukin 6) and cytotoxic activity of NK (Natural Killer) cells. Complementation in biological activity of muramyl dipeptide (MDP) and tuftsin in conjugates proved to be beneficial in the field of immunoadjuvanticity. Our investigations proved that new conjugates acquired features that native immunomodulators did not reveal separately. In examined compound, the part responsible for inducing cytotoxic activity of NK cells was the tuftsin part of the conjugates. MDP in conjugates was responsible for compound-induced synthesis of TNFalpha. The results of our study imply usefulness of the examine compounds (mainly A and B), as potential therapeutic agents.

Recent developments in the synthesis and biological activity of muramylpeptides.

Derivatives of muramyl dipeptide (MDP) are considered as immunostimulants and adjuvants in the immunotherapy of cancer and infections. The interest in these compounds is mainly related to a high variety of their structure and biological properties. Here, we describe the synthesis and biological activity of several recently developed classes of MDP analogues. We also report potential of these analogues in the treatment of cancer and infectious diseases in experimental systems and cancer patients.