A study of polymethyl methacrylate as a substrate for biosensors and dental materials

Abstract

For the first part of the research, an in-vitro study was carried out to determine the calculus removal efficacy of vinegar and its effect on denture base polymer and orthodontic stainless steel wire following repeated immersions. Sectioned orthodontic retainers with calculus deposits following immersion in 100-12.5% vinegar solution, tap water, and effervescent tablets, and mechanical debridement were digitally analyzed for their efficiency. A minimum immersion of 2 hr in 25% vinegar solution attained efficiency of 74.13±22%. Whereas, tap water and effervescent tablets had 15% and 49% efficiency, respectively. AES results showed that diffusion of Ca ions from calculus as a plausible mechanism. One-way ANNOVA and Tukey's test (p≤0.05) showed undiluted vinegar solution affected the flexural strength of PMMA. There was no significant difference in hardness and FTIR spectrum between the groups. Concentrated vinegar had the potential to cause corrosion of the SS wires. Vinegar can be useful in the removal of calculus from dental appliances but should be used in diluted forms to minimize side effects. For the second part of the research, photoactive hydrogel polymer was used for the solid-phase immobilization of commercially available ABO antibodies (Abs) on a Surface Plasmon Resonance (SPR) sensor chip to detect ABO antigens present on the membrane of human red blood cells (RBCs). PMMA was spin-coated onto a SPR chip to provide an anchoring surface for hydrogel polymer, which was spin-coated and partially cross-linked with UV-energy dosage of 0.6 J/cm2 at 254 nm. Microarray printing platform was utilized to deposit murine monoclonal IgM ABO Abs at 1-10% (v/v) onto the sensor surface and further irradiated for crosslinking. RBCs at 1-5% (v/v) was flowed to the sensor surface for analyzing the antigen-antibody interactions using SPR sensorgram and imaging. The regenerative capacities of the sensor surface were studied using 5mM HCl, 5mM NaOH, and deionized water (DI) along with the effects of refrigeration. The immobilized Ab on the SPR chip showed specificity to the corresponding antigens. At Week 1, the response with 1% RBC B was 897.11±196.67 μRIU, 3118.73±308.63 μRIU, and 3048.34±28.97 μRIU at 1%, 5%, and 10% Anti-B, respectively, and with 5% RBC B the response was 565.03±271.87 μRIU at 1% Anti-B, 6237.87±318.46 μRIU at 5% Anti-B, and 7283.44±57.71 μRIU at 10% Anti-B. On the other hand, the response at 10% Anti-A was 309.82±34.57 and 293.66±39.45 μRIU with 1% and 5% RBC B, respectively. Despite some non-specific interactions, the signal-to-noise ratio remained acceptable at 22-25:1 with 5% RBC. The sensor surface could be successfully regenerated using DI water, but there was a drop in response of approx. 100 μRIU/cycle. The sensor chips could be stored at 4°C up to 3 weeks with some degenerative effects. A quick and simplified solid phase immobilization of protein on a SPR sensor chip was attained using the photoactive hydrogel polymer and microarray printing platform.