Antimicrobial resistance (AMR) is recognised globally as one of the greatest threats to human and animal health; thus, discovery of alternative antibacterial agents to address AMR is a priority challenge. This study constitutes the first report of a low-melting temperature, polymer- extrusion process for the smart delivery of thermally-sensitive antimicrobial bioactives, including generally-regarded-as-safe (GRAS) bioactives derived from various sources. Bioactives were assessed before and after extrusion by determining their respective minimum inhibitory concentrations (MIC). WHO-priority AMR-bacterial isolates causing zoonotic infections were evaluated along with use of standard ATCC strains. Findings revealed that this copolymer method was capable of delivering thermally-sensitive bioactives with varying degrees of growth inhibition against the AMR-bacterial strains. The extrusion process was found to increase the effect of nisin against MRSA (4-fold increase) and L. monocytogenes (6.4-fold increase), silver nitrate (AgNO₃) against E. coli (3.6-fold increase) and S. epidermidis (1.25-fold increase), and chitosan against S. aureus (1.25-fold). Findings show the potential applicability of this polymer extrusion process for developing future bioactive-loaded polymer compounds; thus, highlighting the potential of converging bio-based industry with novel materials for enabling 'One-Health' solutions.

This study was performed to develop an adjuvant therapy in the form of a self-administered vaginal tablet regimen for the localized delivery of chemotherapeutic drugs. This therapy will help to reduce relapse by eradicating cancerous cells in the margin of cervical tumors. The vaginal tablet is a very common formulation that is easy to manufacture, easy to place in the vagina, and has a low cost of manufacture, making them ideal for use in developing countries. A combination of disulfiram and 5-fluorouracil, which are both off-patent drugs and provide different modes of action, were evaluated. The tablets developed were evaluated for weight variation, thickness, hardness, friability, swelling index, differential scanning calorimetry (DSC), particle morphology, in vitro drug release, and cytotoxicity on Ca-Ski cells. Both layers were designed to release both drugs concurrently for a synergistic effect. The polymer–polymer interaction between the layers was able to reduce the loss of formulation due to chitosan. While the bilayer tablet had satisfactory performance in the physicochemical tests, in vitro cell culture with Ca-Ski also showed a synergistic effect using a combination of drugs at a low dose. However, the formulation only had 24-h dose release before degradation. Further drug combinations should be evaluated in subsequent studies.

Antimicrobial resistance (AMR) has become a topic of great concern in recent years, with much effort being committed to developing alternative treatments for resistant bacterial pathogens. Drug combinational therapies have been a major area of research for several years, with modern iterations using combining well-established antibiotics and other antimicrobials with the aim of discovering complementary mechanisms. Previously, we characterised four GRAS antimicrobials that can withstand thermal polymer extrusion processes for novel medical device-based and therapeutic applications. In the present study, four antimicrobial bioactive—silver nitrate, nisin, chitosan and zinc oxide—were assessed for their potential combined use as an alternative synergistic treatment for AMR bacteria via a broth microdilution assay based on a checkerboard format. The bioactives were tested in arrangements of two-, three- and four-drug combinations, and their interactions were determined and expressed in terms of a synergy score. Results have revealed interesting interactions based on treatments against recognised test bacterial strains that cause human and animal infections, namely E. coli, S. aureus and S. epidermidis. Silver nitrate was seen to greatly enhance the efficacy of its paired treatment. Combinations with nisin, which is a lantibiotic, exhibited the most interesting results, as nisin has no effect against Gram-negative bacteria when used alone; however, it demonstrated antimicrobial effects when combined with silver nitrate or chitosan. This study constitutes the first study to both report on practical three- and four-drug combinational assays and utilise these methods for the assessment of established and emerging antimicrobials. The novel methods and results presented in this study show the potential to explore previously unknown drug combination compatibility measures in an ease-of-use- and high-throughput-based format, which can greatly help future research that aims to identify appropriate alternative treatments for AMR, including the screening of potential new bioactives biorefined from various sources.

Biofilm-mediated antimicrobial resistance remains a significant challenge for healthcare and patient safety. Currently, there are gaps in standardised methods for assessing antimicrobials against biofilm formations such as (1) assessment of initial bacterial attachment inhibition, as well as (2) assessment of antimicrobial compounds against both the external biofilm mass and biofilm-embedded metabolically active bacteria. The aim of this study is to address these gaps by combining several anti-biofilm techniques. In the procedure96-well anti-biofilm assessments were performed using plate well and lid peg growth surfaces so as to determine the effects of bioactive compounds (silver nitrate (AgNO₃), nisin, chitosan and zinc oxide nanopowder (ZnO)) on biofilm growth inhibition, formed biofilm reduction and bacterial attachment inhibition. These studies focused on the initial attachment stage against in vitro biofilms of P. aeruginosa and S. aureus. Effects were measured against biofilm mass using Crystal Violet (CV) staining, while embedded bacteria metabolic activity was measured using Resazurin. AgNO₃ exhibited significant inhibition and reduction against P. aeruginosa at all stages of biofilm development (p < 0.0001). AgNO₃ showed significant results against S. aureus during biofilm development and against the embedded, metabolically active population of established biofilms (p < 0.0001). Nisin showed significant inhibition against S. aureus biofilm populations (p < 0.0001). Chitosan showed significant increases in S. aureus biofilm formations following exposure, during initial attachment (p < 0.02), during biofilm growth (p < 0.0001) and against formed biofilm populations (p < 0.0001). ZnO showed significant increases during initial attachment exposure (p < 0.0001), but also exhibited growth inhibition (p < 0.0001) and biofilm reduction (p < 0.0001). Although variance in anti-biofilm efficacy was evident depending upon treatment used, Gram-staining phenotype and test growth surfaces, this combinational method offers potential for high throughput screening and for evaluating pipeline bioactives isolated from different environments for biofilm prevention, inhibition and removal. Additionally, this approach will help elucidate the relationship between bacteria of interest and biofilm mitigation.