Purpurin 18 derivatives with a polyethylene glycol (PEG) linker were synthesized as novel photosensitizers (PSs) with the goal of using them in photodynamic therapy (PDT) for cancer. These compounds, derived from a second-generation PS, exhibit absorption at long wavelengths; considerable singlet oxygen generation and, in contrast to purpurin 18, have higher hydrophilicity due to decreased logP. Together, these properties make them potentially ideal PSs. To verify this, we screened the developed compounds for cell uptake, intracellular localization, antitumor activity and induced cell death type. All of the tested compounds were taken up into cancer cells of various origin and localized in organelles known to be important PDT targets, specifically, mitochondria and the endoplasmic reticulum. The incorporation of a zinc ion and PEGylation significantly enhanced the photosensitizing efficacy, decreasing IC50 (half maximal inhibitory compound concentration) in HeLa cells by up to 170 times compared with the parental purpurin 18. At effective PDT concentrations, the predominant type of induced cell death was apoptosis. Overall, our results show that the PEGylated derivatives presented have significant potential as novel PSs with substantially augmented phototoxicity for application in the PDT of cervical, prostate, pancreatic and breast cancer.

Nandrolone–pheophorbide a fluorescent conjugate exhibiting promising potential in targeting of androgen receptor-positive cancer cells and their destruction by photodynamic therapy.

Fluorescent sterol probes, comprising a fluorophore connected to a sterol backbone by means of a linker, are promising tools for enabling high-resolution imaging of intracellular cholesterol. In this study, we evaluated how the size of the linker, site of its attachment and nature of the fluorophore, affect the localization and trafficking properties of fluorescent sterol probes. Varying lengths of linker using the same fluorophore affected cell penetration and retention in specific cell compartments. A C-4 linker was confirmed as optimal. Derivatives of heterocyclic sterol precursors attached with identical C-4 linker to different fluorophores at diverse positions also showed significant differences in their binding properties to various intracellular compartments and kinetics of trafficking. Two novel red-emitting probes with good cell permeability, fast intracellular labelling and slightly different distribution displayed very promising characteristics for sterol probes. These probes also strongly labelled endo/lysosomal compartment in cells with pharmacologically disrupted cholesterol transport, or with a genetic mutation of cholesterol transporting protein NPC1, that overlapped with filipin staining of cholesterol. Overall, the present study demonstrates that the physicochemical properties of the fluorophore/linker pairing determine the kinetics of uptake and distribution and subsequently influence the applicability of final probes.

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The phenolic compounds p-hydroxyacetophenone and catechin have been extracted from Norway spruce needles with pure methanol, 80 and 50% (v/v) aqueous methanol, pure acetonitrile, 80% (v/v) aqueous acetonitrile, and pure water. Extraction efficiency of the individual solvents was compared. Although 80% aqueous methanol is the solvent most frequently used for extraction of soluble phenolic compounds from needles, it was found that pure methanol is a more suitable extraction solvent. Surprisingly, a two-step procedure based on the extraction of crushed needles with water then re-extraction with methanol proved a good alternative to direct extraction with methanol. Extraction of uncrushed spruce needles might indicate that relatively more p-hydroxyacetophenone than catechin was located in the surface layer of the needle.