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 concept behind photodynamic therapy (PDT) is being successfully applied in different biomedical contexts such as cancer diseases, inactivation of microorganisms and, more recently, to improve wound healing and tissue regeneration. The effectiveness of PDT in skin treatments is associated with the role of reactive oxygen species (ROS) produced by a photosensitizer (PS), which acts as a “double agent”. The release of ROS must be high enough to prevent microbial growth and, simultaneously, to accelerate the immune system response by recruiting important regenerative agents to the wound site. The growing interest in this subject is reflected by the increasing number of studies concerning the optimization of relevant experimental parameters for wound healing via PDT, namely, light features, the structure and concentration of the PS, and the wound type and location. Considering the importance of developing PSs with suitable features for this emergent topic concerning skin wound healing, in this review, a special focus on the achievements attained for each PS class, namely, of the non-porphyrinoid type, is given.

The upcycling of food waste into high-value materials presents a key opportunity for sustainable waste management. While onion peel (OP) extracts have been investigated as additives for bioplastics, this study explores the direct incorporation of whole powdered OP (5-20 wt%) into starch-based films, eliminating extraction steps and fully valorizing this agro-industrial by-product. Using starch recovered from potato processing slurries as the polymeric matrix, the influence of OP on film structure, mechanical performance, water resistance, gas permeability, and antioxidant activity was evaluated. Chemical analysis of OP revealed a composition of 47% alcohol insoluble compounds (mainly pectin and cellulose), 12% alcohol soluble matter (primarily glucose-based carbohydrates), 6% lipids, 2%proteins, 5% gallic acid equivalents, and 27% ashes. The direct incorporation of powdered OP resulted in natural pigmentation, producing transparent films with an orangish hue. This approach enhances the aesthetic properties of films while eliminating the need for artificial dyes, contributing to a more sustainable product design. The developed bioplastics exhibited enhanced mechanical properties and improved water resistance, making them attractive for sustainable packaging applications. At OP concentrations above 10 wt%, Young's modulus increased from 1214 MPa to 1496 MPa, while tensile strength and elongation at break decreased from 31.4 MPa to 24.6 MPa and from 4.5% to 2.1%, respectively. Water contact angles increased from 75° up to 87°, and water vapor permeability was reduced by up to 60%, improving moisture resistance. Importantly, OP incorporation did not compromise oxygen (O₂), carbon dioxide (CO₂), or nitrogen (N₂) barrier properties and imparted significant antioxidant activity, with 20 wt% OP-based films inhibiting 93% of the 2.2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic) acid radical cation (ABTS^.+) after 6 h. This study presents an innovative waste-to-resource strategy that eliminates processing waste, aligns with circular economy principles, and demonstrates the first use of whole OP as a multifunctional additive in starch-based bioplastics. By replacing conventional extraction-based approaches, this method enhances material sustainability while promoting a scalable, zero-waste approach to packaging development.

Dual probe porphyrin-gold nanorod polyelectrolyte microcapsules were developed to explore the enhancing effects of a plasmonic interface of self-assembled gold nanoparticles in the fluorescence emission from porphyrins loaded into the capsules’ core. An analysis of fluorescence lifetime imaging microscopy (FLIM) data reports a notable 10⁵–10⁶-fold increase in the maximum detected photon rates from diffraction-limited spots and an overall six-fold increase in fluorescence as averaged over the whole microcapsule area. Large emission enhancements were correlated with decreases in fluorescence lifetimes. The microcapsule’s design proved effective in achieving high fluorescent hybrids and may shed light on new possibilities for advanced materials imaging applications.