Enhanced antimicrobial efficacy of chlorhexidine‑encapsulated halloysite nanotubes incorporated in presurgical orthopedic appliances: an in vitro, controlled study

Abstract
Aims and objective Presurgical infant’s orthopedic appliances (PSIOs) play an increasingly crucial role in the interdisciplinary
management of neonatal CLP, aiming to improve and maintain adequate nasolabial aesthetics, followed by primary
lip/nasal surgery in both unilateral and bilateral CLP cases. The use of PSIOs in cleft lip and palate patients can lead to
contamination with oral microflora, acting as a potential reservoir for infectious microorganisms. Acrylic surfaces might
provide retention niches for microorganisms to adhere, and inhabit, which is difficult to control in immunocompromised
patients, thus predisposing them to increased infection risks. The objective of this multi-assay in vitro study was to investigate
the effects of incorporating chlorhexidine-loaded halloysite nanotubes (CHX-HNTs) fillers on the morphological,
cytotoxic, release, and antimicrobial characteristics of self-cured acrylic polymethyl methacrylate (PMMA) material used
in pre-surgical orthopedic appliances.
Methods Disk-shaped PMMA specimens were prepared with varying proportions of CHX-HNTs. A control group without
any addition served as a reference, and four experimental samples contained a range of different concentrations of CHXHNTs
(1.0, 1.5, 3, and 4.5 wt%). The antimicrobial efficacy was assessed using an agar diffusion test against common
reference microorganisms: Candida albicans, Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus
agalactiae. Cytotoxicity was examined using the L929 cell line (mouse fibroblasts) through a (3-[4,5-dimethylthiazol-
2-yl]-2,5-diphenyl tetrazolium bromide, MTT) cell viability assay. The release kinetics of CHX were monitored using
UV-spectral measurements. The statistical analysis used a one-way ANOVA followed by Tukey’s post hoc test.
Results The integration of CHX-HNTs in PMMA exhibited a substantial dose-dependent antifungal and antibacterial
effect against microorganisms at tested mass fractions (1.0 to 4.5 wt%). CHX release was sustained for up to 60 days, supporting
prolonged antimicrobial activity. Furthermore, no significant cytotoxicity was determined in the L929 fibroblast
cell line (control), indicating the biocompatibility of the CHX-HNTs-enhanced PMMA.
Conclusion Incorporating CHX-HNTs in PMMA successfully enhanced its antimicrobial properties, providing sustained
CHX release and superior antimicrobial efficacy. These findings demonstrate the potential of antimicrobial nanoparticles
in dental therapies to improve therapeutic outcomes. However, rigorous further clinical trials and observational studies
are warranted to validate the practical application, safety, and efficacy.
Clinical relevance This study has the potential to make a major impact on the health of infants born with cleft lip and
palate by helping to reduce the prevalence of infectious illnesses. The incorporation of CHX-HNTs into PMMA-based
appliances is a novel promising preventive approach to reduce microbial infections.
Keywords Polymethyl methacrylate resin, halloysite nanotubes · Chlorhexidine gluconate · Antimicrobial activity ·
https://doi.org/10.1007/s00784-023-05464-7

Nadia Bassim Al-Ansari

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