Tsuimin Tsai

Improved photodynamic inactivation of gram-positive bacteria using hematoporphyrin encapsulated in liposomes and micelles

Antimicrobial photodynamic inactivation (PDI) is a promising treatment modality for local infections. To increase the efficacy of photosensitizer, hematoporphyrin (Hp) was used as a model drug and encapsulated in liposomes and micelles. The bactericidal efficacy of the carrier‐entrapped Hp was assessed against gram‐positive bacteria.

ALA-PDT results in phenotypic changes and decreased cellular invasion in surviving cancer cells.

The mechanisms of photodynamic therapy (PDT) have been studied on the cellular and tissue levels. However, the cellular behaviors of cancer cells survived from PDT are still not clear. This study attempted to investigate the influence of 5‐aminolevulinic acid (ALA)‐based PDT on the invasion ability as well as molecular changes in surviving cancer cells and their progeny.

Photodynamic therapy outcome for oral verrucous hyperplasia depends on the clinical appearance, size, color, epithelial dysplasia, and surface keratin thickness of the lesion

Our previous studies showed that oral verrucous hyperplasia (OVH) lesions can be successfully treated with a topical 5-aminolevulinic acid-mediated photodynamic therapy (topical ALA-PDT) protocol using a 635-nm light-emitting diode light source. In this study, we report the clinical outcomes of 36 OVH lesions treated by this protocol and assess what clinicopathological parameters of OVH lesions could influence PDT treatment outcomes. We found that all the 36 OVH lesions showed complete response (CR) after an average of 3.8 (range, 1-6) treatments of topical ALA-PDT. OVH lesions with an clinical appearance of a mass, with the greatest diameter <1.5 cm, with the pink color, with epithelial dysplasia, or with the surface keratin layer < or =40 microm needed significantly less mean treatment numbers of PDT to achieve a CR than OVH lesions with an outer appearance of a plaque or a combination type of peripheral plaque and central mass (p=0.000), with the greatest diameter > or =1.5 cm (p=0.011), with the white color (p=0.000), without epithelial dysplasia (p=0.043), or with the surface keratin layer > 40 microm(p=0.003), respectively. Multivariate analysis showed that only the clinical appearance of OVH lesions was the independent factor (p=0.0069). We conclude that complete regression of OVH lesions can be achieved by less than seven treatments of topical ALA-PDT once a week. The PDT treatment outcome for OVH depends on the outer appearance, size, color, epithelial dysplasia, and surface keratin thickness of the lesion.

Chitosan Augments Photodynamic Inactivation of Gram-Positive and Gram-Negative Bacteria

ABSTRACT Antimicrobial photodynamic inactivation (PDI) was shown to be a promising treatment modality for microbial infections. This study explores the effect of chitosan, a polycationic biopolymer, in increasing the PDI efficacy against Gram-positive bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, and methicillin-resistant S. aureus (MRSA), as well as the Gram-negative bacteria Pseudomonas aeruginosa and Acinetobacter baumannii. Chitosan at <0.1% was included in the antibacterial process either by coincubation with hematoporphyrin (Hp) and subjection to light exposure to induce the PDI effect or by addition after PDI and further incubation for 30 min. Under conditions in which Hp-PDI killed the microbe on a 2- to 4-log scale, treatment with chitosan at concentrations of as low as 0.025% for a further 30 min completely eradicated the bacteria (which were originally at ∼108 CFU/ml). Similar results were also found with toluidine blue O (TBO)-mediated PDI in planktonic and biofilm cells. However, without PDI treatment, chitosan alone did not exert significant antimicrobial activity with 30 min of incubation, suggesting that the potentiated effect of chitosan worked after the bacterial damage induced by PDI. Further studies indicated that the potentiated PDI effect of chitosan was related to the level of PDI damage and the deacetylation level of the chitosan. These results indicate that the combination of PDI and chitosan is quite promising for eradicating microbial infections.

Chitosan Nanoparticles for Antimicrobial Photodynamic Inactivation: Characterization and In Vitro Investigation†

The growing resistance to antibiotics has rendered antimicrobial photodynamic inactivation (PDI) an attractive alternative treatment modality for infectious diseases. Chitosan (CS) was shown to further potentiate the PDI effect of photosensitizers and was therefore used in this study to investigate its ability to potentiate the activity of erythrosine (ER) against bacteria and yeast. CS nanoparticles loaded with ER were prepared by ionic gelation method and tested for their PDI efficacy on planktonic cells and biofilms of Streptococcus mutans, Pseudomonas aeruginosa and Candida albicans. The nanoparticles were characterized for their size, polydispersity index and zeta potential. No toxicity was observed when planktonic cells and biofilms were treated with the nanoparticles in the dark. However, when the cells were exposed to light irradiation after treatment with free ER or ER/CS nanoparticles, a significant phototoxicity was observed. The antimicrobial activity of ER/CS nanoparticles was significantly higher than ER in free form. The particle size and incubation time of the nanoparticles also appeared to be important factors affecting their PDI activity against S. mutans and C. albicans.

Topical 5-aminolevulinic acid-mediated photodynamic therapy for oral verrucous hyperplasia, oral leukoplakia and oral erythroleukoplakia

BACKGROUND Our previous studies showed that a new topical 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) protocol using a light-emitting diode (LED) light source is an effective and successful treatment modality for oral verrucous hyperplasia (OVH). In this study, we reported and compared the clinical outcomes of 24 OVH lesions, 97 oral leukoplakia (OL) lesions and 6 oral erythroleukoplakia (OEL) lesions treated with topical ALA-PDT in the National Taiwan University Hospital, Taipei, Taiwan from November 2001 to December 2005. METHODS Twenty-four OVH lesions, 65 OL lesions and 6 OEL lesions were treated with topical ALA-PDT once a week and 32 OL lesions were treated with the same topical ALA-PDT twice a week. Their clinical outcomes between two different groups were compared by Chi-square test. RESULTS All the 24 OVH lesions treated once a week showed complete response (CR) after 1-6 (mean, 3.5) treatments of ALA-PDT. The 65 OL lesions treated with topical ALA-PDT once a week showed CR in 5, partial response (PR) in 33 and no response (NR) in 27. The 32 OL lesions treated with the same topical ALA-PDT twice a week demonstrated CR in 11 and PR in 21. The 32 OL lesions treated twice a week had a significantly better clinical outcome than the 65 OL lesions treated once a week (P<0.001). The six OEL lesions treated with topical ALA-PDT once a week showed CR in four and PR in two. The 6 OEL lesions treated once a week had a significantly better clinical outcome than the 65 OL lesions treated once a week (P<0.001). CONCLUSION We conclude that complete regression of OVH lesions can be achieved by less than seven treatments of topical ALA-PDT once a week. OL lesions treated twice a week have a significantly better clinical outcome than OL lesions treated once a week. In addition, OEL lesions treated once a week have a significantly better clinical outcome than OL lesions treated once a week.

The use of chitosan to enhance photodynamic inactivation against Candida albicans and its drug-resistant clinical isolates

Drug-resistant Candida infection is a major health concern among immunocompromised patients. Antimicrobial photodynamic inactivation (PDI) was introduced as an alternative treatment for local infections. Although Candida (C.) has demonstrated susceptibility to PDI, high doses of photosensitizer (PS) and light energy are required, which may be harmful to eukaryotic human cells. This study explores the capacity of chitosan, a polycationic biopolymer, to increase the efficacy of PDI against C. albicans, as well as fluconazole-resistant clinical isolates in planktonic or biofilm states. Chitosan was shown to effectively augment the effect of PDI mediated by toluidine blue O (TBO) against C. albicans that were incubated with chitosan for 30 min following PDI. Chitosan at concentrations as low as 0.25% eradicated C. albicans; however, without PDI treatment, chitosan alone did not demonstrate significant antimicrobial activity within the 30 min of incubation. These results suggest that chitosan only augmented the fungicidal effect after the cells had been damaged by PDI. Increasing the dosage of chitosan or prolonging the incubation time allowed a reduction in the PDI condition required to completely eradicate C. albicans. These results clearly indicate that combining chitosan with PDI is a promising antimicrobial approach to treat infectious diseases.

Photodynamic inactivation of chlorin e6-loaded CTAB-liposomes against Candida albicans.

Antimicrobial photodynamic inactivation (PDI) is a promising therapeutic modality for the treatment of local infections. To increase the efficacy of PDI, chlorine e6 (Ce6) was encapsulated in cationic CTAB‐liposomes composed of various ratios of dimyristoyl‐sn‐glycero‐phosphatidylcholine (DMPC) and the cationic surfactant, cetyltrimethyl ammonium bromide (CTAB). The PDI efficacy of the liposomal‐Ce6 was assessed in vitro against susceptible and drug‐resistant clinical isolates of Candida albicans (C. albicans) as well as in infected burn wounds.

Dual-effect liposomes encapsulated with doxorubicin and chlorin e6 augment the therapeutic effect of tumor treatment.

Long circulating doxorubicin (Dox)‐loaded PEGylated liposomes are clinically safer than the free form due to the significant reduction of cardiac toxicity. However, the therapeutic efficacy of the PEGylated liposome could further be improved if poor diffusivity and slow drug release of the liposome in tumor interstitium can be overcome. In this study, a dual‐effect liposome triggered by photodynamic effect was developed to improve the therapeutic efficacy of Dox‐loaded PEGylated liposomes.

Chloride intracellular channel 4 involves in the reduced invasiveness of cancer cells treated by photodynamic therapy.

The mechanisms of photodynamic therapy (PDT) have been studied on the cellular and tissue levels. However, the cellular behaviors of cancer cells survived from PDT are still not clear. Previously, we have found that PDT‐derived variants A375/3A5 and A375/6A5 have reduced invasion ability. This study attempted to further elucidate the possible molecules associated with the altered invasiveness in the PDT‐derived variants and cancer cells treated with PDT.