Microorganisms, usually bacteria and fungi, grow and spread in skin wounds, causing infections. These infections trigger the immune system and cause inflammation and tissue damage within the skin or wound, slowing down the healing process. The use of photodynamic therapy (PDT) to eradicate microorganisms has been regarded as a promising alternative to anti-infective therapies, such as those based on antibiotics, and more recently, is being considered for skin wound-healing, namely for infected wounds. Among the several molecules exploited as photosensitizers (PS), porphyrinoids exhibit suitable features for achieving those goals efficiently. The capability that these macrocycles display to generate reactive oxygen species (ROS) gives a significant contribution to the regenerative process. ROS are responsible for avoiding the development of infections by inactivating microorganisms such as bacteria but also by promoting cell proliferation through the activation of stem cells which regulates inflammatory factors and collagen remodeling. The PS can act solo or combined with several materials, such as polymers, hydrogels, nanotubes, or metal-organic frameworks (MOF), keeping both the microbial photoinactivation and healing/regenerative processes’ effectiveness. This review highlights the developments on the combination of PDT approach and skin wound healing using natural and synthetic porphyrinoids, such as porphyrins, chlorins and phthalocyanines, as PS, as well as the prodrug 5-aminolevulinic acid (5-ALA), the natural precursor of protoporphyrin-IX (PP-IX).

The molecular interactions of anionic tetrasulfonate phenyl porphyrin (TPPS) with poly(amido amine) (PAMAM) dendrimers of generation 2.0 and 4.0 (G2 and G4, respectively) forming H- or J-aggregates, as well as with human and bovine serum albumin proteins (HSA and BSA), were reviewed in the context of self-assembly molecular complementarity. The spectroscopic studies were extended to the association of aluminum phthtalocyanine (AlPCS₄) detected with a PAMAM G4 dendrimer with fluorescence studies in both steady state and dynamic state, as well as due to the fluorescence quenching associated to electron-transfer with a distribution of lifetimes. The functionalization of TPPS with peripheral substituents enables the assignment of spontaneous pH-induced aggregates with different and well-defined morphologies. Other work reported in the literature, in particular with soft self-assembly materials, fall in the same area with particular interest for the environment. The microencapsulation of TPPS studies into polyelectrolyte capsules was developed quite recently and aroused much interest, which is well supported and complemented by the extensive data reported on the Imaging Microscopy section of the Luminescence of Porphyrins and Phthalocyanines included in the present review.

The self aggregation behaviour of meso-tetraarylporphyrins containing two carboxyphenyl units in adjacent and opposite positions, respectively, 5,10-bis(4-carboxyphenyl)-15,20-diphenylporphyrin (DiCPP-adj) and 5,15-bis(4-carboxyphenyl)-10,20-diphenylporphyrin (DiCPP-opp), was investigated at different pH values. Ordered porphyrin architectures are obtained at pH = 0.8 and pH = 12 for both compounds studied, through an easy self assembly approach. The type of architecture and the extent of aggregation are related with the relative positions of the 4-carboxyphenyl groups attached to the porphyrin core and with the counterions present. The aggregates obtained exhibit spontaneous chirality, resonance light scattering, short fluorescence lifetimes and low fluorescence quantum yields. The data gives evidence that at pH = 0.8 with NO₃ ⁻ the preferred aggregation is more favoured for DiCPP-adj than for DiCPP-opp, whereas at pH = 12 the aggregate of DiCPP-opp is induced by Na⁺ and Li⁺ cations and stabilized by hydrophobic interactions. Deposition of aqueous solutions at key pHs on glass surfaces enables the detection of circular and ring aggregates viewed by fluorescence lifetime imaging microscopy (FLIM) with dimensions of a few micrometres.