One of the major impediments to drug development is low aqueous solubility and thus poor bioavailability, which leads to insufficient clinical utility. Around 70–80% of drugs in the discovery pipeline are suffering from poor aqueous solubility and poor bioavailability, which is a major challenge when one has to develop an ocular drug delivery system. The outer lipid layer, pre-corneal, dynamic, and static ocular barriers limit drug availability to the targeted ocular tissues. Biopharmaceutical Classification System (BCS) class II drugs with adequate permeability and limited or no aqueous solubility have been extensively studied for various polymer-based solubility enhancement approaches. The hydrophilic nature of cellulosic polymers and their tunable properties make them the polymers of choice in various solubility-enhancement techniques. This review focuses on various cellulose derivatives, specifically, their role, current status and novel modified cellulosic polymers for enhancing the bioavailability of BCS class II drugs in ocular drug delivery systems.

Cellulosic Polymers for Enhancing Drug Bioavailability in Ocular Drug Delivery Systems.

This study focuses on the kinetics of a pure strain of bacterium Rhodococcus sp. SKC, isolated from phenol-contaminated soil, for the biodegradation of phenol as its sole carbon and energy source in aqueous medium. The kinetics of phenol biodegradation including the lag phase, the maximum phenol degradation rate, maximum growth rate (Rm) and maximum yield coefficient (Y) for each Si (initial phenol concentration, mg/L) were fitted using the Gompertz and Haldane models of substrate inhibition (R2 > 0.9904, RMSE < 0.00925). The values of these parameters at optimum conditions were μmax = 0.30 h-1, Ks = 36.40 mg/L, and Ki = 418.79 mg/L, and that means the inhibition concentration of phenol was 418.79 mg/L. By comparing with other strains of bacteria, Rhodococcus sp. SKC exhibited a high yield factor and tolerance towards phenol. This study demonstrates the potential application of Rhodococcus sp. SKC for the bioremediation of phenol contaminate.

https://www.mdpi.com/1420-3049/25/16/3665/pdf

Biodegradation of Phenol by Rhodococcus sp. Strain SKC: Characterization and Kinetics Study

Heteronuclear multiple-quantum coherence (HMQC) pulse sequences for establishing heteronuclear correlation in solid-state nuclear magnetic resonance (NMR) between 35 Cl and 1 H nuclei in chloride salts under fast (60 kHz) magic-angle spinning (MAS) and at high magnetic field (a 1 H Larmor frequency of 850 MHz) are investigated. Specifically, recoupling of the 35 Cl-1 H dipolar interaction using rotary resonance recoupling with phase inversion every rotor period or the symmetry-based SR421 pulse sequences are compared. In our implementation of the population transfer (PT) dipolar (D) HMQC experiment, the satellite transitions of the 35 Cl nuclei are saturated with an off-resonance WURST sweep, at a low nutation frequency, over the second spinning sideband, whereby the WURST pulse must be of the same duration as the recoupling time. Numerical simulations of the 35 Cl-1 H MAS D-HMQC experiment performed separately for each crystallite orientation in a powder provide insight into the orientation dependence of changes in the second-order quadrupolar-broadened 35 Cl MAS NMR lineshape under the application of dipolar recoupling. Two-dimensional 35 Cl-1 H PT-D-HMQC MAS NMR spectra are presented for the amino acids glycine·HCl and l-tyrosine·HCl and the pharmaceuticals cimetidine·HCl, amitriptyline·HCl and lidocaine·HCl·H2 O. Experimentally observed 35 Cl lineshapes are compared with those simulated for 35 Cl chemical shift and quadrupolar parameters as calculated using the gauge-including projector-augmented wave (GIPAW) method: the calculated quadrupolar product (PQ ) values exceed those measured experimentally by a factor of between 1.3 and 1.9.

35 Cl-1 H Heteronuclear correlation magic-angle spinning nuclear magnetic resonance experiments for probing pharmaceutical salts.

The feasibility of using ultrahigh-performance liquid chromatography (UHPLC) in combination with high-resolution time-of-flight mass spectrometry (TOFMS) for simultaneous identification and determination of quaternary ammonium compounds and other active ingredients (gramicidin C, tyrothricin, benzocaine, oxybuprocaine, fenoterol) in various dosage forms was assessed. Analytes were identified using retention times, exact ion masses, and coincidence of isotope distribution patterns (mSigma). The detection limit and limit of quantitation were 0.01 – 0.05 and 0.05 – 0.1 ng/mL (ng/g), respectively, for all studied compounds. The ranges of determined concentrations were 0.01(0.05) – 100 ng/mL (ng/g). The method was verified using actual drugs. The relative standard deviation of the analytical results was ≤ 0.1.

Simultaneous Identification and Determination by LC-MS of Quaternary Ammonium Compounds with Other Active Ingredients in Drugs

Development of sunlight-driven photodynamic inactivation film to extend the shelf life of chilled mutton

Modern antimicrobial preservatives authorized for use in dosage form technology are reviewed. The nomenclature and various classifications of preservatives according to chemical nature, mechanism and spectrum of antimicrobial action, optimum effective concentrations for antimicrobial activity, and separate factors affecting the activity of antimicrobial preservatives in various dosage forms, e.g., optimum solution pH values and specific adsorbents reducing preservative activity, are presented. Antimicrobial preservatives used widely in pharmaceutical technology, i.e., parabens, sorbic acid and its salts, benzoic acid and its salts, and benzalkonium chloride, are discussed in detail. Ascience-based approach to selecting antimicrobial preservatives is shown to produce the most stable and safest medicines.

E. S. Panteleeva

Papers

Modern Preservatives of Microbiological Stability (Review)