The challenges associated with solubility and bioavailability of porphyrinoid-type photosensitizers in photodynamic therapy require solutions that are based on modern drug carriers, including polymeric nanoparticles. With that in mind this review discusses poly(lactic-co-glycolic acid, PLGA)-based polymeric nanoparticles encapsulating selected well-known photosensitizers, such as protoporphyrin IX, tetrahydroxyphenylporphyrin, chlorin e6, and tetracarboxyphenylporphyrin, with a view to the physicochemical and biological properties. Also discussed are their potential medical applications towards photodynamic and sonodynamic therapy. PLGA-based nanoparticles, encapsulating photosensitizers, were analysed in terms of particle size, surface charge, morphology, loading efficiency, release kinetics, and stability. Moreover, the cellular uptake and subcellular localisation of carriers were considered in correlation to polymer composition and surface functionalisation. Special attention was given to how PEGylation, lipid-hybrid coatings, or the incorporation of additional therapeutic or imaging agents has modulated both the physicochemical properties and biological activities of photosensitizers. The comparative assessment of different porphyrinoid-based photosensitizers highlighted how hydrophobicity, amphiphilicity, and molecular structure have an influence on encapsulation efficiency and therapeutic outcomes. Furthermore, issues such as the premature release of photosensitizers, along with limited bioavailability, and limited penetration through biological barriers were addressed as well as some proposed mitigation strategies. Overall, this review highlights the versatility of PLGA nanoparticles as a powerful platform for photosensitizer delivery, with promising implications for advancing polymer-based nanomedicine and improving the efficacy of photodynamic therapy.

The study’s aim was to synthesize new unsymmetrical sulfanyl zinc(II) porphyrazines and subject them to physicochemical and electrochemical characterization and also an initial acute toxicity assessment. The procedure was initiated from a commercially available dimercaptomaleonitrile disodium salt and o-phthalonitrile using Linstead’s macrocyclization reaction conditions, which led to magnesium(II) tribenzoporphyrazine with 4-(3,5-dibutoxycarbonylphenoxy)butylthio substituents. The obtained macrocycle was demetallated with trifluoroacetic acid and subsequently remetallated with zinc(II) acetate toward the zinc(II) porphyrazine derivative. The zinc(II) tribenzoporphyrazine with 4-(3,5-dibutoxycarbonylphenoxy)butylthio substituents was then subjected to the reduction reaction with LiAlH₄, yielding zinc(II) tribenzoporphyrazine with 4-[3,5-di(hydroxymethyl)phenoxy]butylthio substituents. The new zinc(II) tribenzoporphyrazines were characterized by UV-Vis spectroscopy, various NMR techniques (¹HNMR, ¹³CNMR, ¹H-¹H COSY, ¹H-¹³C HSQC, and ¹H-¹³C HMBC), and mass spectrometry. In the UV-Vis spectra, both macrocycles revealed characteristic Soret and Q-bands, whose positions were dependent on the solvent used for the measurements. Zinc(II) tribenzoporphyrazines were studied using electrochemical and photochemical methods, including the singlet oxygen generation assessment. Both zinc(II) porphyrazines revealed high singlet oxygen generation quantum yield values of up to 0.59 in DMSO, which indicates their potential photosensitizing potential for photodynamic therapy. In addition, new derivatives were subjected to a Microtox^® bioluminescence assay.