Photoantimicrobial Biohybrids by Supramolecular Immobilization of Cationic Phthalocyanines onto Cellulose Nanocrystals

Abstract

The development of photoactive and biocompatible nanostructures is a highly desirable goal to address the current threat of antibiotic resistance. Here, we describe a novel supramolecular biohybrid nanostructure based on the non-covalent immobilization of cationic zinc phthalocyanine (ZnPc) derivatives onto unmodified cellulose nanocrystals (CNC), following an easy and straightforward protocol, in which binding is driven by electrostatic interactions. These non-covalent biohybrids show strong photodynamic activity against S. aureus and E. coli, representative examples of Gram-positive and Gram-negative bacteria, respectively, and C. albicans, a representative opportunistic fungal pathogen, outperforming the free ZnPc counterparts and related nanosystems in which the photosensitizer is covalently linked to the CNC surface.

Superior performance of macroporous over gel type polystyrene as a support for the development of photo-bactericidal materials

“…aPDI can be applied using soluble 12 or supported photosensitizers. [13][14][15][16][17][18][19][20] A broad number of chemical families have been proposed as effective generators of ROS, especially singlet oxygen ( 1 O 2 ). 21 Among those molecules, xanthenic dyes, phenothiazinium compounds, porphyrins and phthalocyanins have been studied.…”

“…[24][25][26][27][28][29][30][31][32][33][34][35] Regarding the supports for the photoactive agents, a variety of materials have been described in the literature, like polyurethane, cellulose, nylon, chitosan, silica and polystyrene. [13][14][15][16][17][18][19][20] This last polymer is one of the most popular supports employed so far, dating back to the pioneering works of Schaap and Neckers. 36 Polystyrene is a versatile system, used in applications as diverse as fluorescence sensing 37 or catalysis.…”

Selective Photoinactivation of Methicillin‐Resistant Staphylococcus aureus by Highly Positively Charged RuII Complexes

“…[9][10][11] However,t he same modes of action of PDT and aPDT raise a great challenge in selectively inactivating bacterialc ells but leavingm ammalian cells unaffected.U nlike mammalian cells, in whicha cidic phospholipidsa re mainly located in the inner leafleto fp lasma membranes, acidic phospholipids andn egatively chargedc omponents, such as teichuronic acid (for Gram positive bacteria, for example, S. aureus)a nd lipopolysaccharide (for Gram negative bacteria, for example, E. coli)a re mainly locatedi nt he outer edges of cell walls or outer membranes, making the bacterial surface highly negatively charged. [12,13] This disparity has been leveraged to develop cationic aPDT agents, such as triarylmethanes [14,15] and borondipyrromethene (BODIPY)d yes bearing two positive charges, [16] peryleneb earing four positive charges, [17] porphyrins, [18][19][20][21][22][23] phthalocyanines [24] and bacteriochlorin [25,26] bearing three, four, or eight positive charges, with the aim to achieve higher binding affinity toward bacteria.T hough these photosensitizers showed remarkable inactivation capability against bacterial cells, in several cases, phototoxicity towardm ammalianc ells was observed, [14,23] suggestingl imited selectivity of the aPDT agents. For example,atriarylmethane dye reduced CFU of E. coli by 5log units at 1 mm upon irradiation, but only 60 %A 549 cells were alive undert he same conditions.…”

“…Hamblin and co-workers foundc ationic porphyrins were taken up more rapidly by microbial cells than mammalianc ells, whichw as utilized to improve selectivityb yas hort incubation time (30 min), [25,26] but will complicate clinicala pplication. In most cases, [16][17][18][19][20][21][22]24] the selectivity between bacterial and mammalian cells of theseaPDT agentswas not reported.…”

“…Though many types of highly positively charged organic photosensitizers have been studied for aPDT application, their phototoxicity towardm ammalian cells was rarely examined. [14][15][16][17][18][19][20][21][22][23][24] In af ew cases, photodamage toward mammalian cells was observed. [14,23] For example, the cationic porphyrincationic antimicrobial peptides( magainin and buforin) conjugates exhibited strongi nteraction as well as photoactivity toward human fibroblasts.…”