ICG supported on carnosine and hydroxyapatite functionalized graphene oxide: a novel photosynthesizer in photodynamic therapy against Streptococcus mutans

A particular attention has been paid to antimicrobial photodynamic therapy (aPDT) as a new method for removing the bacterial contaminants such as Streptococcus mutans (S. mutans) from the tooth surface. Photosensitizer (PS), like indocyanine green (ICG), is a key portion of this technique. The usage of ICG is limited due to its instability. An appropriate nanocarrier with enhanced antibacterial effects could overcome these limitations. The ICG-loaded various nanocarriers including graphene oxide (GO), GO-carnosine (Car) and GO-Car/Hydroxyapatite (HAp) were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Filed Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS) and Ultraviolet-Visible spectrometry (UV–Vis). The UV–Vis spectrometry indicated the successful loading of ICG onto nanocarriers. Due to the porous structure of HAp, the GO-Car/ HAp nanocomposite showed the highest amount of ICG loading (57.52%). UV–Vis spectrometry analysis disclosed a red shift for the characteristic peak of ICG-loaded nanocarriers, which was matched the wavelength of near-infrared (NIR) laser applied for aPDT. The colony forming unit and crystal violet assays were performed to evaluate the antimicrobial and anti-biofilm properties of PSs against S. mutans bacteria.The GO@ICG, GO-Car@ICG and GO-Car/HAp@ICG mediated aPDT, dramatically declined the count of S. mutans strains approximately 91.2%, 95.5% and 93.2%, respectively (P < 0.05). The GO@ICG, GO-Car@ICG, GO-Car/HAp@ICG significantly suppress the S. mutans biofilm formation by 51.4%, 63.8%, and 56.8% (P < 0.05), respectively. Car significantly promoted the antibacterial effect of GO that resulted GO-Car as a novel nanocarreir with a highly inhibitory effects on bacterial survival of S. mutans bacteria. In addition, ICG-loaded into the obtained nanoplatforms proposed an effective nano PS with the application in aPDT to treat the oral infections

Keywords:

Streptococcus mutans , antimicrobial photodynamic therapy , indocyanine green