Date of Completion

2025

Document Type

Thesis

Degree Name

Bachelor of Science in Pharmacy

Keywords

Antimicrobial photodynamic therapy (aPDT), aloe-emodin (AE), chitosan (CS), hydrogel, methicillin-resistant Staphylococcus aureus (MRSA), polyvinyl alcohol (PVA), solid lipid nanoparticles (SLNs), and reactive oxygen species (ROS)

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of resistant skin and soft tissue infections, posing a critical threat in both hospital and community settings. Antimicrobial photodynamic therapy (aPDT) offers a promising alternative treatment by using light-activated photosensitizers to generate reactive oxygen species (ROS) that disrupt bacterial viability. This study aimed to determine the antimicrobial photodynamic activity of a polyvinyl alcohol/chitosan (PVA/CS) hydrogel loaded with aloe-emodin solid lipid nanoparticles (AE-SLNs) and sodium thiocyanate (NaSCN) (AE-SLN/SCN-HPC) against MRSA. AE was encapsulated using glyceryl monostearate and Tween 80 via high-speed stirring and bath ultrasonication. AE-SLNs with NaSCN were then incorporated into PVA/CS (18:2) crosslinked with 2% sodium tripolyphosphate (STPP). The formulations were characterized for particle size (optical microscopy, FE-SEM, and DLS), morphology and structure, drug encapsulation efficiency (DEE%) and drug loading capacity (DL%), swelling, and thermal stability. Antimicrobial activity against MRSA (ATCC 43300) was evaluated using turbidimetric and colony counting methods after irradiation with blue light (488 nm). A cell-free H2DCFDA fluorescence assay was used to assess dose-dependent ROS generation. AE-SLNs exhibited mean particle sizes of 79.57-158.30 nm with a polydispersity index of 0.22, high drug encapsulation efficiency (90.56%), and high drug loading capacity (90.26%). The optimized PVA/CS hydrogel (18:2, 2% STPP) exhibited >99% drug encapsulation efficiency, high swelling, and uniform morphology. Upon irradiation, AE-SLN/SCN-HPC achieved 85.74% inhibition in OD600 turbidimetry and a log reduction equivalent to that of 0.1% benzalkonium chloride (BZK) at 12 mg in the colony counting assay. ROS fluorescence increased 13-fold for AE-SLN/SCN HPC, while 6-fold for AE-SLN-HPC after 10 minutes of irradiation, with ROS levels comparable to 0.3% hydrogen peroxide (H2O2). AE-SLN/SCN-HPC presents a novel and promising delivery system for targeted, light-triggered treatment of resistant bacterial infections, with broad implications for the future of aPDT in managing superficial MRSA infections.

First Advisor

Sigfredo B. Mata, RPh

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