The development of photoactive and biocompatible nanomaterials is a current major challenge of materials science and nanotechnology, as they will contribute to promoting current and future biomedical applications. A growing strategy in this direction consists of using biologically inspired hybrid materials to maintain or even enhance the optical properties of chromophores and fluorophores in biological media. Within this area, porphyrinoids constitute the most important family of organic photosensitizers. The following extensive review will cover their incorporation into different kinds of photosensitizing biohybrid materials, as a fundamental research effort toward the management of light for biomedical use, including technologies such as photochemical internalization (PCI), photoimmunotherapy (PIT), and theranostic combinations of fluorescence imaging and photodynamic therapy (PDT) or photodynamic inactivation (PDI) of microorganisms.

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.

No abstract

The family of subphthalocyanine (SubPc) macrocycles represents an interesting class of nonplanar aromatic dyes with promising features for energy conversion and optoelectronics. The use of SubPcs in biomedical research is, on the contrary, clearly underexplored, despite their documented high fluorescence and singlet oxygen quantum yields. Herein, for the first time it is shown that the interaction of these chromophores with light can also be useful for theranostic applications, which in the case of SubPcs comprise optical imaging and photodynamic therapy (PDT). In particular, the article evaluates, through a complete in vitro study, the dual-role capacity of a novel series of SubPcs as fluorescent probes and PDT agents, where the macrocycle axial substitution determines their biological activity. The 2D and 3D imaging of various cancer cell lines (i.e., HeLa, SCC-13, and A431) has revealed, for example, different subcellular localization of the studied photosensitizers (PS), depending on the axial substituent they bear. These results also show excellent photocytotoxicities, which are affected by the PS localization. With the best dual-role PS, preliminary in vivo studies have demonstrated their therapeutic potential. Overall, the present paper sets the bases for an unprecedented biomedical use of these well-known optoelectronic materials.

Herein we describe a photosensitizer (PS) with the capacity to perform multiple logic operations based on a pyrene-containing phthalocyanine (Pc) derivative. The system presents three output signals (fluorescence at 377 and 683 nm, and singlet oxygen ((1)O2) production), which are dependent on three inputs: two chemical (concentration of dithiothreitol (DTT) and acidic pH) and one physical (visible light above 530 nm for (1)O2 sensitization). The multi-input/multioutput nature of this PS leads to single-, double-, and triple-mode activation pathways of its fluorescent and photodynamic functions, through the interplay of various interrelated AND, ID, and INHIBIT gates. Dual fluorescence emissions are potentially useful for orthogonal optical imaging protocols while (1)O2 is the main reactive species in photodynamic therapy (PDT). We thus expect that this kind of PS logic system will be of great interest for multimodal cellular imaging and therapeutic applications.

Cellulose, a cheap and abundant biomaterial, leads to photosensitizing biohybrids through the immobilization of cationic phthalocyanine dyes onto the surface of cellulose nanocrystals. These biohybrids are efficient and broad‐spectrum photoantimicrobial agents against opportunistic fungal pathogens, Gram‐positive, and Gram‐negative bacteria. More information can be found in the Full Paper by T. Torres, M. A. Kostiainen, et al. on page 4320 ff.