B, P, and S heteroatom doped, bio- and hemo-compatible 2D graphitic-carbon nitride (g-C₃N₄) with antioxidant, light-induced antibacterial, and bioimaging endeavors

Abstract

The synthesis of 2D graphitic g-C3N4 and heteroatom-doped graphitic H@g-C3N4 (H: B, P, or S) particles were successfully done using melamine as source compounds and boric acid, phosphorous red, and sulfur as doping agents. The band gap values of 2D g-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4 structures were determined as 2.90, 3.03, 289, and 2.93 eV, respectively. The fluorescent emission wavelengths of 2D g-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4 structures were observed at 442, 430, 441, and 442 nm, respectively upon excitation at λEx=325 nm. There is also one additional new emission wavelength was found at 345 nm for B50@g-C3N4 structure. The blood compatibility test results of g-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4 structures revealed that all materials are blood compatible with <2% hemolysis and >90%blood clotting indices at 100 µg/mL concentration. The cell toxicity of the prepared 2D graphitic structures were also tested on L929 fibroblast cells, and even the heteroatom doped has g-C3N4 structures induce no cytotoxicity was observed with >91% cell viability even at 250 µg/mL particle concentration with the exception of P50@g-C3N4 which as >75 viability. Moreover, for 2D g-C3N4, B50@g-C3N4, and S50@g-C3N4 constructs, even at 500 µg/mL concentration, >90% cell viabilities was monitored. As a diagnostic material, B50@g-C3N4 was found to have significantly high penetration and distribution abilities into L929 fibroblast cells granting a great potential in fluorescence imaging and bioimaging applications. Furthermore, the elemental doping with B, P, and S of g-C3N4 were found to significantly increase the photodynamic antibacterial activity e.g., more than half of bacterial elimination by heteroatom-doped forms of g-C3N4 under UVA treatment was achieved.

Polydopamine Coating of Graphitic Carbon Nitride, g-C3N4, Improves Biomedical Application

“…Figure 4 a depicts the UV–Vis DRS spectra of the g-C 3 N 4 and PDA@g-C 3 N 4 structures, and Figure S3 shows the reflectivity wavelength diagram used to determine the band gaps of the g-C 3 N 4 -based structures. The band gap of g-C 3 N 4 is determined to be 2.72 eV, which is consistent with previously reported g-C 3 N 4 structures [ 31 , 52 , 53 , 54 ]. The coating of g-C 3 N 4 with PDA, on the other hand, shifts the band gap to lower levels.…”

“…Biocompatibility and hemocompatibility tests were performed according to the literature [ 31 ], and details are given in the Supplementary Material .…”

“…where 'QY' is fluorescence quantum yield, 'I' is the integrated fluorescence intensity, 'OD' is the UV-vis absorbance, and 'η' is the refractive index of the solvents used for the g-C 3 N 4 -based structure suspension solutions, water (η = 1.333) and 0. Biocompatibility and hemocompatibility tests were performed according to the literature [31], and details are given in the Supplementary Material.…”