D-to-E and T19V Variants of the pH-Low Insertion Peptide and Their Doxorubicin Conjugates Interact with Membrane at Higher pH Ranges Than WT.

To improve targeted cargo delivery to cancer cells, pH-Low Insertion Peptide (pHLIP) variants were developed to interact with the membrane at pH values higher than those of the WT. The Asp-to-Glu variants aim to increase side chain pKa without disturbing the sequence of protonations that underpin membrane insertion. The Thr19 variants represent efforts to perturb the critical Pro20 residue. To study the effect of cargo on pHLIP insertion, doxorubicin (Dox), a fluorescent antineoplastic drug, was conjugated to selected variants near the inserting C-terminus. Variants and conjugates were characterized on a POPC membrane using Trp and Dox fluorescence methods to define the entire pH range of insertion (pHinitial-pHfinal). Compared to WT with a pHi-pHf range of 6.7-5.6, D25E-D31E-D33E, D14E-D25E-D31E-D33E, and T19V-D25E variants demonstrated higher pHi-pHf ranges of 7.3-6.1, 7.3-6.3, and 8.2-5.4, respectively. The addition of Dox expanded the pHi-pHf range, mainly by shifting pHi to higher pH values (e.g., WT pHLIP-Dox has a pHi-pHf range of 7.7-5.2). Despite the low Hill coefficient observed for the conjugates, D14E-D25E-D31E-D33E pHLIP-Dox completed insertion by a pHf of 5.7. However, the Dox cargo remained in the hydrophobic membrane interior after pHLIP insertion, which may impede drug release. Finally, a logistic function can describe pHLIP insertion as a peripheral-to-TM (start-to-finish) two-state transition; wherever possible, we discuss data deviating from such sigmoidal fitting in support of the idea that pH-specific intermediate states distinct from the initial peripheral state and the final TM state exist at intervening pH values.

Anti-bacterial efficacy of alcoholic hand rubs in the Kenyan market, 2015.

BACKGROUND: Hand hygiene is known to be effective in preventing hospital and community-acquired infections. The increasing number of hand sanitizer brands in Kenyan hospitals and consumer outlets is of concern. Thus the main aim of this study was to evaluate the anti-bacterial efficacy and organoleptic properties of these hand sanitizers in Kenya. METHODS: This was an experimental, laboratory-based study of 14 different brands of hand sanitizers (coded HS1-14) available in various retail outlets and hospitals in Kenya. Efficacy was evaluated using standard non-pathogenic Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) as per the European Standard (EN). The logarithmic reduction factors (RF) were assessed at baseline and after treatment, and log reduction then calculated. Ten and 25 healthy volunteers participated in the efficacy and organoleptic studies respectively. RESULTS: Four (28.6%) hand sanitizers (HS12, HS9, HS13 and HS14) showed a 5.9 reduction factor on all the three bacteria strains. Seven (50%) hand sanitizers had efficacies of <3 against all the three bacteria strains used. Efficacy on E. Coli was higher compared to the other pathogens. Three hand sanitizers were efficacious on one of the pathogens and not the other. In terms of organoleptic properties, gel-based formulations were rated far higher than the liquid based formulations brands. CONCLUSION: Fifty percent (50%) of the selected hand sanitizers in the Kenyan market have efficacy that falls below the World Health Organization (WHO) and DIN EN 1500:2013. Of the 14 hand sanitizers found in the Kenyan market, only four showed efficacies that were comparable to the WHO-formulation. There is a need to evaluate how many of these products with <3 efficacy that have been incorporated into the health system for hand hygiene and the country's policy on regulations on their usage.