Antimicrobial peptide series(DermaGen)

DPK-060 is a synthetic, 17 amino acid peptide, structurally derived from the human protein kininogen. DPK-060 mainly acts by membrane disruption mechanism, thus demonstrating strong broad-spectrum antimicrobial activity against both gram-positive and gram-negative microbes, including methicillin-resistant S. aureus (MRSA) in-vitro and in-vivo. Apart from its antimicrobial effect, DPK-060 also possesses anti-inflammatory activity. In addition, DPK-060 has demonstrated positive results in phase II clinical trials in atopic dermatitis (AD) patients; but was not statistically conclusive due to the instability of DPK-060 as a drug substance in the formulation. Thus, the present investigation was aimed to assess and compare the efficacy of DPK-060 nanostructured lipid (NLC) based gel with conventional formulations (free DPK-060 gel and lotion) in AD mice animal models. DPK-060 loaded NLCs were formulated by meltemulsification technique and loaded into Carbopol 934 P gel and characterized for various physicochemical parameters such as particle size, zeta-potential, shape and surface morphology, rheological parameters, in-vitro drug release, cytotoxicity, cellular uptake, ex-vivo skin permeation/deposition, in-vitro antimicrobial activity, and proteolytic stability studies. NLCs exhibited 85 % encapsulation with 6.7 % loading efficacy, a size, and zeta potential of 128.6 nm and -22.5 mv, respectively. Additionally, DPK-060 NLC gel demonstrated controlled release and a better permeation profile in comparison to free DPK-060 gel and lotion. A substantial reduction in pro-inflammatory cytokines levels and improvement in AD lesions was achieved by DPK-060 NLC gel compared to free DPK-060 gel and lotion-based formulations. The present study confirms that DPK-060 NLC gel-based formulation can be an effective, safe, and novel alternative for the treatment of AD.

In the present study, we investigate degradable anionic dendritic nanogels (DNG) as carriers for antimicrobial peptides (AMPs). In such systems, the dendritic part contains carboxylic acid-based anionic binding sites for cationic AMPs, whereas linear poly(ethylene glycol) (PEG) chains form a shell for promotion of biological stealth. In order to clarify factors influencing membrane interactions of such systems, we here address effects of nanogel charge, cross-linking, and degradation on peptide loading/release, as well as consequences of these factors for lipid membrane interactions and antimicrobial effects. The DNGs were found to bind the AMPs LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES) and DPK-060 (GKHKNKGKKNGKHNGWKWWW). For the smaller DPK-060 peptide, loading was found to increase with increasing nanogel charge density. For the larger LL-37, on the other hand, peptide loading was largely insensitive to nanogel charge density. In line with this, results on the secondary structure, as well as on the absence of stabilization from proteolytic degradation by the nanogels, show that the larger LL-37 is unable to enter into the interior of the nanogels. While 40-60% nanogel degradation occurred over 10 days, promoted at high ionic strength and lower cross-linking density/higher anionic charge content, peptide release at physiological ionic strength was substantially faster, and membrane destabilization not relying on nanogel degradation. Ellipsometry and liposome leakage experiments showed both free peptide and peptide/DNG complexes to cause membrane destabilization, indicated also by antimicrobial activities being comparable for nanogel-bound and free peptide. Finally, the DNGs were demonstrated to display low toxicity towards erythrocytes even at peptide concentrations of 100 µM.