Substrates for Simultaneous Antimicrobial Drug Delivery and Protein Cleaning

Objectives: Our objective for this research is to design and prepare tools that can effectively target and prevent the formation and growth of biofilm in response to the metabolic activities of cariogenic bacteria.
Methods: We embarked on a two-step functionalization process of metal and metal oxide substrates. First, the substrates underwent thiolation/silanization, followed by the Menshutkin reaction, which sequentially introduced quaternary pyridinium salts (QPS) onto the surfaces. Subsequently, we integrated chlorhexidine (CHX), an oral antimicrobial agent, onto the modified substrates through an acid-base interaction. The characterization of substrate modification and drug loading was carried out using X-ray photoelectron spectroscopy monitoring changes in the atomic concentration of surface elements. Additionally, we explored the interaction between QPS and CHX using nuclear magnetic resonance (NMR) spectroscopy. To assess the pH-responsive protein adsorption, we employed a quartz crystal microbalance with dissipation monitoring (QCM-D) technique to monitor the dynamic adsorption and release of a model protein, bovine serum albumin (BSA), between pH 4-8.
Results: Thiolation was validated through the detection of increased bromine and sulfur elements, rising from zero to 6.0% and 4.6%, respectively. After the Menshutkin reaction, bromine was no longer detected. Consequently, the presence of nitrogen and oxygen elements increased from zero to 5.1% and 4.1%, respectively, aligning closely with the anticipated values based on the chemical structure of QPS. NMR further affirmed the interaction between QPS and CHX, demonstrating broadened aromatic peaks when CHX was introduced to QPS. Additionally, at pH 8, bovine serum albumin (BSA) was adsorbed onto the CHX-loaded substrates, and at pH 4, it was simultaneously released in conjunction with CHX.
Conclusions: We have successfully developed a pH-responsive substrate capable of releasing antimicrobial agents and facilitating protein cleaning simultaneously. This technology exhibits substantial potential for integration into dental implants and orthodontic devices for a healthy local oral microbiome.