Diamond Nanoparticles-Porphyrin mTHPP Conjugate as Photosensitizing Platform: Cytotoxicity and Antibacterial Activity

Abstract

Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to stabilize PS in the biological medium resulting in photosensitizing nanoparticles of enhanced photoactivity. Herein, (Meso-5, 10, 15, 20-tetrakis (3-hydroxyphenyl) phorphyryn (mTHPP) was conjugated with diamond nanoparticles (ND) by covalent bond. Nanoconjugate ND-mTHPP showed suitable stability in aqueous suspension with 58 nm of hydrodynamic diameter and Zeta potential of −23 mV. The antibacterial activity of ND-mTHPP was evaluated against Escherichia coli for different incubation times (0–24 h). The optimal activity was observed after 2 h of incubation and irradiation (660 nm; 51 J/cm2) performed right after the addition of ND-mTHPP (100 μg/mL) to the bacterial suspension. The inhibitory activity was 56% whereas ampicillin at the same conditions provided only 14% of bacterial growth inhibition. SEM images showed agglomerate of ND-mTHPP adsorbed on the bacterial cell wall, suggesting that the antimicrobial activity of ND-mTHPP was afforded by inducing membrane damage. Cytotoxicity against murine embryonic fibroblast cells (MEF) was also evaluated and ND-mTHPP was shown to be noncytotoxic since viability of cells cultured for 24 h in the presence of the nanoconjugate (100 μg/mL) was 78%. Considering the enhanced antibacterial activity and the absence of cytotoxic effect, it is possible to consider the ND-mTHPP nanoconjugate as promising platform for application in antimicrobial photodynamic therapy (aPDT).

Antimicrobial Photodynamic Therapy: Latest Developments with a Focus on Combinatory Strategies

“…Neoteric specimen of PS-CNTs encompass toluidine blue, polypyrrole, malachite green, MB, RB, and porphyrins [156,[252][253][254][255][256][257]. Although purportedly older since it was discovered in the 1960s, diamond NPs or nanodiamonds seemingly remain the lesser known carbon-based nanomaterials to date; nevertheless, the latter dispose of legit aPDT arguments with their fluorescence, photostability, proclivity for conjugation with diverse PSs such as porphyrins or metallated phthalocyanines and silver NPs, but also inherent antibacterial activity [120,[258][259][260][261][262].…”

Novel Concentric Magnetic Continuum Robot with Multiple Stiffness Modes for Potential Delivery of Nanomedicine

“…We prepared this nanomedicine incorporating the photosensitiser m-THPP. The m-THPP is a close congener of the approved photosensitiser 5,10,15,20-tetrakis(3-hydroxyphenyl)chlorin (m-THPC, temoporfin), and they can be used for photodynamic therapy of diseases of the brain, neck and skin diseases [44,45]. The SEM images (Figure 8c) demonstrate that the medicine is on the nanometre scale.…”

The Photosensitizer Temoporfin (mTHPC) – Chemical, Pre‐clinical and Clinical Developments in the Last Decade†‡

“…While the compounds were all taken up by OE33 or SKGT‐4 cells, no phototoxicity was observed at short illumination times (2 min). Similar reactions were used to link m THPC to nanodiamonds (52). Esterifications were also used in the generation of m THPC‐Au‐nanoparticles (AuNPs) (53).…”