Retinoids are a class of compounds derived from vitamin A or having structural and/or functional similarities with vitamin A. They are classified into three generations based on their molecular structures. Inside the body, retinoids bind to several classes of proteins including retinoid-binding proteins and retinoid nuclear receptors. This eventually leads to the activation of specific regulatory regions of DNA - called the retinoic acid response elements - involved in regulating cell growth, differentiation and apoptosis. Several clinical trials have studied the role of topical and systemic retinoids in disease, and research is still ongoing. Currently, retinoids are used in several fields of medicine. This paper aims to review the structure, mechanisms of action, and adverse effects of retinoids, as well as some of their current uses in Dermatology.

Liposomes have been used as delivery vehicles for stabilizing drugs, overcoming barriers to cellular and tissue uptake, and for directing their contents toward specific sites in vivo. Chitosan is a biological macromolecule derived from crustacean shells and has several emerging applications in drug development, obesity control, and tissue engineering. In the present work, the interaction between chitosan and dipalmitoyl phosphatidylcholine (DPPC) liposomes was studied by transmission electron microscopy (TEM), zeta potential, solubilization using the nonionic detergent octylglucoside (OG), as well as Fourier transform infrared (FTIR) spectroscopy and viscosity measurements. The coating of DPPC liposomes by a chitosan layer was confirmed by electron microscope images and the zeta potential of liposomes. Coating of liposome by chitosan resulted in an increase in liposomal size by addition of a layer of 92 +/- 27.1 nm. The liposomal zeta potential became increasingly positive as chitosan concentration increased from 0.1 to 0.3% w/v, then it held at a relatively constant value. The amount of detergent needed to completely solubilize the liposomal membrane was increased after coating of liposomes with chitosan, indicating an increased membrane resistance to the detergent and hence a change in the natural membrane permeation properties. In the analysis of FTIR spectra of DPPC, the symmetric and antisymmetric CH(2) (at 2,800-3,000 cm(-1)) bands and the C=O (at 1,740 cm(-1)) stretching band were investigated in the absence and presence of the chitosan. It was concluded that appropriate combining of the liposomal and chitosan characteristics might be utilized for the improvement of the therapeutic efficacy of liposomes as a drug delivery system.

Scabies is an infestation of the skin by the mite Sarcoptes scabiei. It manifests with pruritic erythematous papules and excoriations, in addition to the pathognomonic burrows. Multiple drugs can be used for treatment, but resistance to conventional therapy is increasing throughout the years. This paper will review the mechanisms of resistance proposed in the literature and some of the potential solutions to this problem.

No abstract

Polyvinylpyrrolidone (PVP) is employed in several potential applications, relying of its special chemical and physical properties in addition to its low toxicity and biocompatibility. The aim of this work is to prepare polyvinylpyrrolidone-silver (PVP-Ag) nanocomposite with high inhibiting effect on the microbial growth and low cytotoxicity. In situ prepared small stable spherical silver nanoparticles, with narrow range particle size distribution, were obtained by easy, economical and rapid chemical reduction method. Silver ions were reduced to silver nanoparticles using low amount of sodium borohydride (NaBH4) as a strong reducing agent. PVP-Ag nanocomposite was prepared using PVP as a stabilizing and capping agent. Formation of the spherical silver nanoparticles with mean particle size 5 nm was confirmed by ultraviolet-visible spectroscopy, high resolution transmission electron microscopy, and dynamic light scattering. The inhibiting growth effect of the nanocomposite toward Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa), and yeast fungus (Candida albicans) were studied. The cytotoxicity of the nanocomposite against BJ1 normal skin fibroblast cell line was tested. Results of this work presented perfect antimicrobial activity of the PVP-Ag nanocomposite towards bacteria and fungi with low cytotoxicity, which may lead to promising applications in skin wound healing.