Abstract
Large-scale use of antibiotics in food animal farms as growth promoters is considered as one of the driving factors behind increasing incidence of microbial resistance. Several alternatives are under investigation to reduce the amount of total antibiotics used in order to avoid any potential transmission of drug resistant microbes to humans through food chain. Copper sulfate and zinc oxide salts are used as feed supplement as they exhibit antimicrobial properties in addition to being micronutrients. However, higher dosage of copper and zinc (often needed for growth promoting effect) to animals is not advisable because of potential environmental toxicity arising from excreta. Innovative strategies are needed to utilize the complete potential of trace minerals as growth promoting feed supplements. To this end, we describe here the development and preliminary characterization of hydrothermally treated chitosan as a delivery vehicle for copper and zinc nanoparticles that could act as a micronutrient-based antimicrobial feed supplement. Material characterization studies showed that hydrothermal treatment makes a chitosan hydrogel that rearranged to capture the copper and zinc metal particles. Systemic antimicrobial assays showed that this chitosan biopolymer matrix embedded with copper (57.6 μg/ml) and zinc (800 μg/ml) reduced the load of model gut bacteria (target organisms of growth promoting antibiotics), such as Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, and Lactobacillus fermentum under in vitro conditions. Particularly, the chitosan/copper/zinc hydrogel exhibited significantly higher antimicrobial effect against L. fermentum, one of the primary targets of antibiotic growth promoters. Additionally, the chitosan matrix ameliorated the cytotoxicity levels of metal supplements when screened against a murine macrophage cell line RAW 264.7 and in TE-71, a murine thymic epithelial cell line. In this proof-of-concept study, we show that by using chitosan as a delivery platform, micronutrient-based metal feed additives could be used to minimize the undesirable levels of microbial population without causing significant cytotoxic effect under in vitro conditions. These findings provide the platform for further studies in target animal models to quantify the required physiological concentrations of copper and zinc when delivered via a chitosan hydrogel platform to elicit a growth promoting effect without causing any toxicity.
Highlights
The World Health Organization recently cautioned that antimicrobial resistance amongst infectious agents has reached alarming levels and that it could turn the twenty-first century into a time where common wound injuries can become lethal infections [1]
We recently demonstrated that hydrothermal (HT) treatment of chitosan results in depolymerization of chitosan into shorter chain polymers with increased functional groups availability for loading high amounts of antimicrobial copper and similar metals [18]
In this proof-of-concept manuscript, we demonstrate the antimicrobial ability of this chitosan–metal composite by screening against model organisms for gut bacteria that are targets of conventional antibiotic growth promoters
Summary
The World Health Organization recently cautioned that antimicrobial resistance amongst infectious agents has reached alarming levels and that it could turn the twenty-first century into a time where common wound injuries can become lethal infections [1]. Developing a strategy that can considerably reduce the frequency of administration of copper and zinc in feed, yet maintaining the growth beneficial effect would be a viable alternative One such strategy would be to increase the gastric retention time of the supplied minerals by embedding the metallic salts in a biocompatible polymer that has affinity for the gastro intestinal tract. By taking advantage of the above-mentioned merits, we developed a chitosan hydrogel matrix that is loaded with both copper and zinc metal nanoparticles that can be used as a potential micronutrient-based antimicrobial feed additive In this proof-of-concept manuscript, we demonstrate the antimicrobial ability of this chitosan–metal composite by screening against model organisms for gut bacteria that are targets of conventional antibiotic growth promoters. We infer that this report will be the foundation for our future studies that will examine this novel material for its growth promoting effects involving target animals
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
