Use of photosensitive molecules in the crosslinking of biopolymers: applications and considerations in biomaterials development

The development of diverse types of biomaterials has significantly contributed to bringing new biomedical strategies to treat clinical conditions. Applications of these biomaterials can range from mechanical support and protection of injured tissues to joint replacement, tissue implants, and drug delivery systems. Among the strategies commonly used to prepare biomaterials, the use of electromagnetic radiation to initiate crosslinking stands out. The predominance of photo-induced polymerization methods relies on a fast, efficient, and straightforward process that can be easily adjusted to clinical needs. This strategy consists of irradiating the components that form the material with photons in the near ultraviolet-visible wavelength range (i.e., ∼310 to 750 nm) in the presence of a photoactive molecule. Upon photon absorption, photosensitive molecules can generate excited species that initiate photopolymerization through different reaction mechanisms. However, this process could promote undesired side reactions depending on the target zone or treatment type (e.g., oxidative stress and modification of biomolecules such as proteins and lipids). This review explores the basic concepts behind the photopolymerization process of ex situ and in situ biomaterials. Particular emphasis was put on the photosensitization initiated by the most employed photosensitizers and the photoreactions that they mediate in aqueous media. Finally, the undesired oxidation reactions at the bio-interface and potential solutions are presented.

On the Jahn-Teller Effect in Silver Complexes of Dimethyl Amino Phenyl Substituted Phthalocyanine

The structures of Ag complexes with dimethyl amino phenyl substituted phthalocyanine m[dmaphPcAg]q of various charges q and in the two lowest spin states m were optimized using the B3LYP method within the D4h symmetry group and its subgroups. The most stable reaction intermediate in the supposed photoinitiation reaction is 3[dmaphPcAg]-. Group-theoretical analysis of the optimized structures and of their electron states reveals two symmetry-descent mechanisms. The stable structures of maximal symmetry of complexes 1[dmaphPcAg]+, 3[dmaphPcAg]+, 2[dmaphPcAg]0, and 4[dmaphPcAg]2- correspond to the D4 group as a consequence of the pseudo-Jahn-Teller effect within unstable D4h structure. Complexes 4[dmaphPcAg]0, 1[dmaphPcAg]-, 3[dmaphPcAg]-, and 2[dmaphPcAg]2- with double degenerate electron ground states in D4h symmetry structures undergo a symmetry descent to stable structures corresponding to maximal D2 symmetry, not because of a simple Jahn-Teller effect but due to a hidden pseudo-Jahn-Teller effect (strong vibronic interaction between excited electron states). The reduction of the neutral photoinitiator causes symmetry descent to its anionic intermediate because of vibronic interactions that must significantly affect the polymerization reactions.

Development of a new near-infrared, spectrophotometric, and colorimetric probe based on phthalocyanine containing mercaptoquinoline unit for discriminative and highly sensitive detection of Ag+, Cu2+, and Hg2+ ions

A new near-infrared, spectrophotometric, and colorimetric probe based on a phthalocyanine-containing mercaptoquinoline unit (MQZnPc) has been constructed and utilized for discriminative and highly selective/sensitive detection of Ag⁺, Cu²⁺, and Hg²⁺ ions by using proper masking agents like EDTA, KI, and NaCl. The probe only responds to Ag⁺, Cu²⁺, and Hg²⁺ among the tested ions without any interference. The probe performs quite well (the limit of detection: 160 ppb, 148 ppb, and 276 ppb of Ag⁺, Cu²⁺, and Hg²⁺ions for UV-Vis, and 15 ppb, 37 ppb, and 467 ppb of Ag⁺, Cu²⁺, and Hg²⁺ ions for fluorescence, respectively), and has a fast response time (150 sec, 90 sec, and 90 sec of Ag⁺, Cu²⁺, and Hg²⁺ions for UV-Vis, and 300 sec, 240 sec, and 90 sec Ag⁺, Cu²⁺, and Hg²⁺ions for fluorescence, respectively). The probe also displays a colorimetric feature for UV-Vis and smartphone applications. Based on a single probe, Ag⁺, Cu²⁺, and Hg²⁺ ions which are the main toxic water contaminants could be recognized very quickly and colorimetrically with high recovery values in tap water samples. This study stands out with its unique properties compared to the related studies in the literature.

A new highly Selective, sensitive and NIR spectrophotometric probe based on A2B2-Type of unsymmetrical phthalocyanine for hazardous Be2+ recognition

The aim of this work is to construct a new A₂B₂-type of unsymmetrical and ratiometric phthalocyanine (Pc) based-probe O-A₂B₂ZnPc to provide an effective solution to critical inadequacy to be experienced for the detection of hazardous Be²⁺. O-A₂B₂ZnPc enabling strong absorption and emission in Near-Infrared region (λ_abs-λ_em wavelengths of 694-712 nm) showed excellent selectivity and sensitivity toward Be²⁺ among competitive metal ions by both spectrophotometric and fluorometric methods. The probe with oligomeric Pc form in THF was degraded with the addition of aqueous Be²⁺ and arranged to J-aggregation form, resulting in a remarkably diminishing in Q-band at 694 nm as well as a new band formation at 746 nm, and a considerably decreasing in fluorescence emission. The probe has superior features for the determination of Be²⁺ such as high quantum efficiency and photochemical stability, rapid response (1 s), high selectivity and very low Limit of Detection (0.26 ppb and 1.5 ppb) for UV-Vis and fluorescence, respectively which are quite good values according to the permissible amount of Be²⁺ (4 ppb) in water as specified by World Health Organization. O-A₂B₂ZnPc can be shown among the best performing probes with its unique properties according to previous studies in the literature. In addition, the geometrical and spectral features of the O-A₂B₂ZnPc were analyzed in detail by DFT calculations.

Electrochemically Deposited Zinc (Tetraamino)phthalocyanine as a Light-activated Antimicrobial Coating Effective against S. aureus

Light-activated antimicrobial coatings are currently considered to be a promising approach for the prevention of nosocomial infections. In this work, we present a straightforward strategy for the deposition of a photoactive biocidal organic layer of zinc (tetraamino)phthalocyanine (ZnPcNH2) in an electrochemical oxidative process. The chemical structure and morphology of the resulting layer are widely characterized by microscopic and spectroscopic techniques, while its ability to photogenerate reactive oxygen species (ROS) is investigated in situ by UV-Vis spectroscopy with α-terpinene or 1,3-diphenylisobenzofuran as a chemical trap. It is shown that the ZnPcNH2 photosensitizer retained its photoactivity after immobilization, and that the reported light-activated coating exhibits promising antimicrobial properties towards Staphyloccocus aureus (S. aureus).

Morphology induced enhanced photoconductivity of a phthalocyanine-based benzimidazole linked two-dimensional conjugated covalent organic polymer

A novel phthalocyanine-based benzimidazole linked conjugated covalent organic polymer (NiPc-COP1) has been synthesized with multiple randomly ordered crystalline morphologies.

Azacalixphyrins as an innovative alternative for the free-radical photopolymerization under visible and NIR irradiation without the need of co-initiators

Azacalixphyrins are unique aromatic macrocycles featuring strong absorption from the visible to the near-infrared (NIR) spectral ranges. This work demonstrates through EPR spin-trapping experiments that the N-alkyl tetrasubstituted azacalixphyrin (ACP) can lead to the formation of carbon-centered radicals initiating for the free-radical photopolymerization (FRP) of bio-based acrylate monomer upon the irradiation of several light emitting diodes, which emissions range from 455 to 660 nm. Compared to other previously reported systems, the tremendous advantage of the ACP photoinitiating system is its ability to promote photopolymerization on its own, avoiding the introduction of co-initiators. A new potential application of this promising photoinitiator is highlighted through the fabrication of well-defined microstructures under NIR laser diode irradiation at λ = 800 nm.