Antifungal effect of poly(methyl methacrylate) containing zinc doped mesoporous silica nanoparticles

Abstract

Denture stomatitis is caused by the accumulation of biofilm on the oral tissues and denture surface, characterized by inflammation and erythema of the oral mucosa beneath dentures, affecting many denture wearers. Zinc oxide nanoparticles (ZnO NPs) are known for their antifungal effects against Candida albicans, a common cause of denture stomatitis. However, incorporating ZnO NPs can negatively impact the mechanical properties of denture base resins. To address this issue, mesoporous silica nanoparticles (MSNs) are introduced due to their ability to enhance mechanical properties by forming a micromechanical interlocking interface between the fillers and the resin matrix. In this study, we incorporated Zn-doped mesoporous silica nanoparticles (Zn-MSNs) into poly(methyl methacrylate) (PMMA) and assessed their impact on surface properties, mechanical strength, and antifungal effects against C. albicans. MSNs and Zn-MSNs were synthesized by a sol–gel method and characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). N2 adsorption/desorption measurements were conducted to obtain the specific surface area and pore size. PMMA specimens were prepared by incorporating ZnO NPs, MSNs, and Zn-MSNs at 1.0 and 5.0 weight percentages (wt.%). The PMMA surface gloss was evaluated using a gloss meter with a 2 mm × 2 mm area and a 60° geometry. Translucency was measured using a spectrophotometer operating in reflectance mode and calibrated using a white tile and a black trap following standard procedures. The flexural strength and flexural modulus were measured by a universal mechanical testing machine according to the International Standard ISO 20795–1. The anti-adhesion assessment was performed by a colony-forming unit (CFU) against C. albicans. TEM images of MSNs and Zn-MSNs were successfully prepared and exhibited spherical morphology with a well-ordered mesoporous structure. ZnO NPs were found to be irregular in shape and had varying sizes and aspect ratios, with some of the particles agglomerating. EDS mapping results of the Zn-MSNs showed the composition and distribution of the Si, O, and Zn elements. Zn was successfully doped with an amount of approximately 7.34 wt.% and homogeneously distributed. According to the IUPAC classification, the N2 adsorption–desorption curves showed typical characteristics of the type IV isotherm of mesoporous materials. BET analysis confirmed the porosity of the Zn-MSNs with a pore size of 3.41 nm, pore volume of 0.77 cm3/g, and surface area of 848 m2/g. The surface gloss observed no significant difference between the control group, the 1% MSN, and the 1% Zn-MSN groups. In contrast, the 1% ZnO group showed a lower gloss value than the 5% MSN and 5% Zn-MSN groups. Moreover, the 5% ZnO group had the lowest surface gloss value among all the groups. Regarding translucency results, no significant difference was observed among all groups with the incorporation of MSNs and Zn-MSNs. However, the 1 wt% ZnO and 5 wt% ZnO groups showed significant differences from the control group. The flexural strength showed no significant difference in the incorporation of 1 wt% of MSN and Zn-MSN groups compared to the control group. However, when the concentration of MSN and Zn-MSN groups was increased to 5 wt%, a significant decrease in flexural strength was observed. Among all groups, the lowest flexural strength value was observed in the 5% ZnO group. Nevertheless, the flexural strength of all groups fulfilled the minimum requirements (60 MPa) specified in ISO 20795-1. As a result of fungal anti-adhesion, the control group showed the highest value, and the denture base resin containing 5 wt% ZnO, 5 wt% MSN, and 5 wt% Zn-MSN showed a significant difference from the control group. Among all values, 5 wt% Zn-MSN showed the lowest value. In this study, denture base resins incorporating ZnO NPs, MSNs, and Zn-MSNs were prepared, and the antifungal effect against C. albicans and clinical applicability were investigated. Incorporating Zn-MSNs into denture base resin exhibited acceptable surface properties, mechanical strength, and effective antifungal activity against C. albicans. Therefore, the denture base resin containing 5 wt% Zn-MSN is expected to be a valuable material for denture. 의치 구내염은 의치 착용자에게 흔하게 발병하는 질환으로, 구강 점막의 염증과 홍반을 특징으로 한다. 산화아연나노입자 (ZnO NPs)는 의치 구내염의 주요 원인 중 하나인 칸디다 알비칸스(Candida albicans)에 대한 항진균 효과를 가지고 있지만, 의치 레진에 직접 첨가할 경우 기계적 특성에 부정적인 영향을 미칠 수 있다. 한편, 메조포러스 실리카 나노입자(MSNs)는 필러와 레진 기질 사이에 미세 기계적 연동 인터페이스를 형성하여 기계적 특성을 향상시키는 능력으로 인해 다양한 분야에서 연구가 활발히 진행되고 있다. 따라서 본 연구에서는 아연이 도핑된 메조포러스 실리카 나노입자(Zn-MSNs)를 폴리메틸 메타크릴레이트(PMMA)에 첨가하여 표면 특성, 기계적 강도, 및 항진균 효과에 미치는 영향을 평가하였다. MSNs과 Zn-MSNs은 졸-겔 방법으로 합성되었으며, 합성된 입자는 메조다공성 구조를 갖는 구형 형태를 나타냈다. PMMA에 준비된 MSNs, ZnO NPs, Zn-MSNs 나노입자를 각각 1 wt%, 5 wt% 첨가하여 실험군을 제작하였고, 아무것도 첨가하지 않은 PMMA를 대조군으로 하였다. 반투명도 결과에서 MSNs과 Zn-MSNs을 첨가한 그룹에서는 대조군과 유의한 차이를 보이지 않았으나 1% ZnO과 5% ZnO은 모두 유의한 차이를 나타냈다(p<0.05). 기계적 특성 실험 결과, 대조군이 가장 높은 값을 보였으며 1% ZnO, 5% MSN, 5% Zn-MSN, 5% ZnO 군과 유의한 차이를 나타냈다(p<0.05). 그 중 5% ZnO은 모든 그룹 중에서 가장 낮은 값을 나타냈다(p<0.05). C. albicans에 대한 항진균 실험 결과 대조군이 가장 높은 균 생존율을 보였으며, 5% ZnO, 5% Zn-MSN과 유의한 차이를 나타냈다(p<0.05). 5 wt% Zn-MSN을 의치상 레진에 첨가하면 5 wt% ZnO를 함유한 의치상 레진에 비해 우수한 표면 특성과 기계적 강도를 나타냈다. 또한 C. albicans에 대한 항진균 실험 결과, 효과적인 항진균 활성을 나타냈다. 결과적으로 Zn-MSN을 5 wt% 함유한 의치상 레진은 의치용 재료로 활용할 수 있는 잠재력이 있음을 시사한다.