In situ detection of ALA-stimulated porphyrin metabolic products in Escherichia coli B by fluorescence line narrowing spectroscopy

Targeted delivery of 5-aminolevulinic acid by multifunctional hollow mesoporous silica nanoparticles for photodynamic skin cancer therapy

5-Aminolevulinic acid (5-ALA) is a precursor of a strong photosensitizer, protoporphyrin IX (PphIX), for photodynamic therapy (PDT). Developing appropriate delivery carriers that can assist 5-ALA in bypassing the lipophilic barrier to directly enter into cancer cells is a research focus. The improved delivery of 5-ALA is even important for skin cancer therapy through PDT process. In this work, targeting ligand folic acid (FA)-functionalized hollow mesoporous silica nanoparticles (HMSNPs) were fabricated to deliver 5-ALA for PDT against B16F10 skin cancer cells. The FA targeting ligand enabled selective endocytosis of 5-ALA loaded HMSNPs into cancer cells. PphIX formed from delivered 5-ALA exhibited high photocytotoxicity to the cancer cells in vitro.

Photodynamic therapy: a new antimicrobial approach to infectious disease?

Photodynamic therapy (PDT) employs a non-toxic dye, termed a photosensitizer (PS), and low intensity visible light which, in the presence of oxygen, combine to produce cytotoxic species. PDT has the advantage of dual selectivity, in that the PS can be targeted to its destination cell or tissue and, in addition, the illumination can be spatially directed to the lesion. PDT has previously been used to kill pathogenic microorganisms in vitro, but its use to treat infections in animal models or patients has not, as yet, been much developed. It is known that Gram-(-) bacteria are resistant to PDT with many commonly used PS that will readily lead to phototoxicity in Gram-(+) species, and that PS bearing a cationic charge or the use of agents that increase the permeability of the outer membrane will increase the efficacy of killing Gram-(-) organisms. All the available evidence suggests that multi-antibiotic resistant strains are as easily killed by PDT as naive strains, and that bacteria will not readily develop resistance to PDT. Treatment of localized infections with PDT requires selectivity of the PS for microbes over host cells, delivery of the PS into the infected area and the ability to effectively illuminate the lesion. Recently, there have been reports of PDT used to treat infections in selected animal models and some clinical trials: mainly for viral lesions, but also for acne, gastric infection by Helicobacter pylori and brain abcesses. Possible future clinical applications include infections in wounds and burns, rapidly spreading and intractable soft-tissue infections and abscesses, infections in body cavities such as the mouth, ear, nasal sinus, bladder and stomach, and surface infections of the cornea and skin.