The spherical nanoparticle-encapsulated chlorhexidine enhances anti-biofilm efficiency through an effective releasing mode and close microbial interactions

published_or_final_versio

The novel spherical/rod-like silica nanoparticles-encapsulated pure chlorhexidine against oral microbes

ePoster: abstract no. 3022OBJECTIVES: Our recent study shows that the pure (freebase, non-salt form) Chlorhexidine (CHX) encapsulated in commercially available mesoporous silica nanoparticles (MSNs) is effective against oral bacterial biofilms (Seneviratne et al, 2014). We further tested the loading efficiency and release profile of CHX encapsulated in our newly synthesized two forms of spherical (S-MSNs) and rod-like MSNs (R-MSNs) (Li et al, 2014). This study investigated the antimicrobial effects of S-MSNs- and R-MSNs-encapsulated pure CHX on selected common oral microbes. METHODS: The minimum inhibitory concentrations (MIC) of S-MSNs- and R-MSNs-encapsulated pure CHX on Streptococcus sobrinus, Streptococcus mutans, Porphyromonas gingivalis and Candida albicans were determined using broth dilution method. Their time-dependent anti-bacterial effects on S. sobrius was evaluated by CFU counting, and their interactions were assessed by field emission scanning electron microscopy (FE-SEM). RESULTS: Overall, both S-MSNs- and R-MSNs-encapsulated pure CHX demonstrated potent antibacterial effects on S. sobrinus, S. mutans, P. gingivalis and C. albicans. The MICs of S-MSNs-encapsulated CHX against these microbes ranged from 3.31 (S. sobrinus) to 93.75 (C. albicans) µg/mL and 3.31 (P. gingivalis) to 125 (S. mutans) µg/mL at 24 h and 48 h, respectively. R-MSNs-encapsulated CHX exhibited higher MICs (27.08-325 µg/mL at 24 h and 27.08-650 µg/mL at 48 h) with reference to the S-MSNs CHX. S-MSNs-encapsulated CHX inhibited continuously on S. sobrius growth at a low saturated concentration through consistent release, during the 72 h experiment period as compared with the R-MSNs CHX (p<0.05). Notably, both forms of MSNs CHX attached on the bacterial surface with potential merge into the cells, while S-MSNs CHX could disperse more homogeneously with reference to R-MSNs CHX. CONCLUSIONS: This pioneering study suggests that the novel S-MSNs-encapsulated pure CHX may exhibit potent and long-lasting antimicrobial effects on these common oral microbes. Further investigation on the underlying mechanisms is highly warranted

Cellular internalization and epithelial penetration of fluorescent-labeled mesoporous silica nanoparticles

Poster Session - Antimicrobial & Host Modulating Approaches to Treat Periodontal Diseases: no. 2022OBJECTIVES: Understanding of cellular internalization and epithelial penetration capacity is crucial to develop the nano-vehicles for drug application in dentistry. This study investigated the cellular uptake, internalization and tissue penetration of our newly synthesized fluorescent spherical mesoporous silica nanoparticles (S-MSNs). METHODS: The fabricated MSNs were surface-modified with amine groups, and subsequently labeled with rhodamine B isothiocyanate (RITC-NP). The RITC-NP fluorescence was detected by fluorescence spectrometer, and the RITC-NP cytotoxicity was evaluated in primary human gingival epithelial cells (HGECs) and differentiated THP-1 cells using CCK-8 kit. Meanwhile, the cellular uptake of RITC-NP was accessed by the confocal scanning laser microscopy after 24h of treatment. Furthermore, the isolated porcine ear skins and reconstituted human gingival epithelia (RHGE) were treated with 200 μg/mL of RITC-NP for 2, 6 and 24 h, and then fixed in 4% paraformaldehyde. The tissue cryosections were stained with DAPI, and subsequently the fluorescence-labeled MSNs were assessed by the fluorescent microscope. The H&E stain was conducted on the cryosections for histological analysis. RESULTS: The RITC-NP (average size of 250 nm) with shifted emission wavelength at 580 nm exhibited a relatively low cytotoxicity on the cells. These labeled-MSNs were mainly distributed around the cellular nuclei after 24 h of treatment. Moreover, the RITC-NP began to penetrate the corneum of porcine ear skin after 2 h of treatment, and notably these particles could be detected in the deep layers of epithelia at 24 h. Interestingly, the RITC-NP accumulated merely in the corneum layer of RHGE during the 24h experiment without causing tissue damage. CONCLUSIONS: This pioneering study demonstrates the penetration and biodistribution of the MSNs in both cells and tissues. It may facilitate further development of nano-based drug delivery for clinical application

Iridium motif linked porphyrins for efficient light-driven hydrogen evolution via triplet state stabilization of porphyrin

202308 bckwAccepted ManuscriptRGCOthersHKBU; NSFC; PolyU; Endowed Professorship in Energy from Ms Clarea AuPublishe

Cocatalyst-free photocatalytic hydrogen evolution with simple heteroleptic iridium(III) complexes

Title in author's file: Co-catalyst-free Photocatalytic Hydrogen Evolution with Simple Heteroleptic Iridium(III) Complexes202308 bckwAccepted ManuscriptRGCOthersState Key Laboratory of Environmental and Biological Analysis; President’s Award for Outstanding Performance in Research Supervision; NSFC; Hong Kong Polytechnic University; Clarea Au for the Endowed Professorship in Energy; Research Institute for Smart Energy (RISE)Publishe