Chemically Modified Polystyrene Co-loaded with Antimicrobial Agents

A recent study showed that at least 50 % of nosocomial infections are due to medical indwelling devices like surgical guides and prosthetics. This amounts to about 2 million patients affected a year. The reason for such statistics is the growth of microorganisms on the surfaces of the medical devices which is known as pathogenesis. In order to remove microbial lifeforms from the surface, methods like sterilization and disinfection have been utilized. However, these methods are unable to completely eliminate the threat of bacterial growth on these devices. There are many attempts to create antimicrobial materials. However, most materials are unable to hold more than one antimicrobial agent without a secondary process. Hence, the objective of the project was to produce an antimicrobial material that can hold more than one antimicrobial agent without the need for a secondary process. The material is produced by sulfonating high impact polystyrene (HIPS) and attaching copper and silver ions. The optimum time of sulfonation between the 1, 2, 3 and 6 hour samples is determined by the degree of sulfonation and ionic exchange capacity. Then, the samples were co-loaded with copper and silver ions of varying ratios for each sample. The efficacy of the antimicrobial properties of the sulfonated HIPS is then tested using a zone of inhibition assay against the raw HIPS and HIPS loaded with antibiotics. Furthermore, TGA, FTIR and DSC data of this new material is also collected. The resultant material is a sulfonated HIPS powder that is pure white in colour. The longer the sulfonation time, the more granulated the appearance of the powder. The 6 hour sample yielded the highest ionic exchange capacity and degree of sulfonation with a sulfonation degree of 33.7 % and an ionic exchange capacity of 2.57 meq/g. This means that the scope of achieving around 30 % sulfonation was achieved. Hence, it was the only sample considered for the rest of the project. The TGA data showed that there is a 6.44 % increment in degradation temperature after sulfonation and then decrement of about 1.6 % when copper and silver ions were added to the sulfonated HIPS sample. When they a mixture of copper and silver ions were added, the degradation temperature increased by 0.77 % compared to the sulfonated HIPS sample. The DSC showed that an increment of 3.29 % in glass transition temperature was seen when sulfonation was done on the HIPS. Further increment of 3 % compared to the sulfonated HIPS sample was seen for all samples bounded with metal ions. There was a higher rate of copper ion binding compared to silver ions binding when the same amount of samples was used when the residual weight was found in the TGA. The sulfonated HIPS-Cu sample is predicted to be more effective against gram negative bacteria while sulfonated HIPS-Ag sample was predicted to be more effective against gram negative bacteria. Overall, the project produced an antimicrobial material for the usage of medical devices. The objectives of the project were achieved.