Light-induced proteolysis of myosin heavy chain by Rose Bengal-conjugated antibody complexes

Design, synthesis and photocytotoxicity of upconversion nanoparticles: Potential applications for near-infrared photodynamic and photothermal therapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) are emerging modalities for the treatment of tumors and nonmalignant conditions, based on the use of photosensitizers to generate singlet oxygen or heat, respectively, upon light (laser) irradiation. They have potential advantages over conventional treatments, being minimally invasive with precise spatial-temporal selectivity and reduced side effects. However, most clinically employed PDT agents are activated at visible (vis) wavelengths for which the tissue penetration and, hence, effective treatment depth are compromised. In addition, the lipophilicity of near-infrared (NIR) photothermal agents limits their use and efficiency. To achieve combined PDT/PTT effects, both excitation wavelengths need to be tuned into the NIR spectral window of biological tissues. This paper reports the synthesis of neodymium-doped upconversion nanoparticles (NaYF₄ :Yb,Er,Nd@NaYF₄ :Nd) that convert 800 nm light into vis wavelengths, which can then activate conventional photosensitizers on the nanoparticle surface for PDT. Covalently bonded IR-780 dyes can readily be activated by 800 nm laser irradiation. The PEGylated nanoplatform exhibited a narrow size distribution, good stability and efficient generation of singlet oxygen under laser irradiation. The in vitro photocytotoxicity of this engineered nanoplatform as either a PDT or PTT agent in HeLa cells is demonstrated, while fluorescence microscopy in nanoplatform-incubated cells highlights its potential for bioimaging.

Aggregation-Induced Emission Gold Clustoluminogens for Enhanced Low-Dose X-ray-Induced Photodynamic Therapy

The use of gold nanoparticles as radiosensitizers is an effective way to boost the killing efficacy of radiotherapy while drastically limiting the received dose and reducing the possible damage to normal tissues. Herein, we designed aggregation-induced emission gold clustoluminogens (AIE-Au) to achieve efficient low-dose X-ray-induced photodynamic therapy (X-PDT) with negligible side effects. The aggregates of glutathione-protected gold clusters (GCs) assembled through a cationic polymer enhanced the X-ray-excited luminescence by 5.2-fold. Under low-dose X-ray irradiation, AIE-Au strongly absorbed X-rays and efficiently generated hydroxyl radicals, which enhanced the radiotherapy effect. Additionally, X-ray-induced luminescence excited the conjugated photosensitizers, resulting in a PDT effect. The in vitro and in vivo experiments demonstrated that AIE-Au effectively triggered the generation of reactive oxygen species with an order-of-magnitude reduction in the X-ray dose, enabling highly effective cancer treatment.

Dual Activity of Rose Bengal Functionalized to Albumin-Coated Lanthanide-Doped Upconverting Nanoparticles: Targeting and Photodynamic Therapy

A modified version of a desolvation method was used to render lanthanide-doped upconverting nanoparticles NaGdF₄:Yb³⁺/Er³⁺ (Ln-UCNPs) water-dispersible and biocompatible for photodynamic therapy. Bovine serum albumin (BSA) was used as surface coating with a direct conjugation to NaGdF₄:Yb³⁺/Er³⁺ nanoparticles forming a ∼2 nm thick shell. It was estimated that approximately 112 molecules of BSA were present and cross-linked per NaGdF₄:Yb³⁺/Er³⁺ nanoparticle. Analysis of the BSA structural behavior on the Ln-UCNP surfaces displayed up to 80% loss of α-helical content. Modification of the Ln-UCNPs with a BSA shell prevents luminescence quenching from solvent molecules (H₂O) with high energy vibrations that can interact with the excited states of the optically active ions Er³⁺ and Yb³⁺ via dipole-dipole interactions. Additionally, the photosensitizer rose bengal (RB) was conjugated to albumin on the surface of the Ln-UCNPs. Emission spectroscopy under 980 nm excitation was carried out, and an energy transfer efficiency of 63% was obtained. In vitro cell studies performed using human lung cancer cells (A549 cell line) showed that Ln-UCNPs coated with BSA were not taken by the cells. However, when RB was conjugated to BSA on the surface of the nanoparticles, cellular uptake was observed, and cytotoxicity was induced by the production of singlet oxygen under 980 nm irradiation.

Effectiveness of erythrosine-mediated photodynamic antimicrobial chemotherapy on dental plaque aerobic microorganisms: A randomized controlled trial

Background:

Dental plaque is one of the predominant causes of major oral diseases. Although mechanical and chemical methods are extensively followed to control the development of plaque, plaque-related diseases still persist. Therefore, this necessitates for alternative measures of plaque control, one such alternative is photodynamic antimicrobial chemotherapy (PACT).

Materials and Methods:

Split mouth randomized clinical trial (CTRI/2017/03/008239) was conducted on 30 participants who reported to the hospital. Participants were asked to rinse their mouth for 1 min using 10 ml of 25 μM erythrosine solutions. Same tooth on both quadrants of the same jaw are selected as the test and control. Intervention used was halogen-based composite curing light with wavelength of 500–590 nm. Plaque sample from the control tooth and test tooth was collected before and after exposure, respectively, and sent to microbiological laboratory for colony count.

Results:

Logarithmic mean and standard deviation of control group with 10² dilutions of aerobic microbial count were found to be 5.34 ± 0.94, and for experimental group, it was 4.47 ± 1.37. The statistical difference between mean CFU values between aerobic bacterial counts was significant (P = 0.006).

Conclusions:

Erythrosine-mediated PACT reduces the extent of dental plaque microbial count and has a potential preventive and therapeutic use in day-to-day life and dental clinics.

Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum

Background:

According to the development of resistant strains of pathogenic bacteria following treatment with antimicrobial chemotherapeutic agents, alternative approaches such as lethal photosensitization are being used. The aim of this study was to evaluate the effect of visible light and laser beam radiation in conjugation with three different photosensitizers on the survival of two main periodontopathogenic bacteria including Porphyromonas gingivalis and Fusobacterium nucleatum in different exposure periods.

Materials and Methods:

In this in vitro prospective study, strains of P. gingivalis and F. nucleatum. were exposed to visible light at wavelengths of 440 nm and diode laser light, Gallium-Arsenide, at wavelength of 830 nm in the presence of a photosensitizer (erythrosine, curcuma, or hydrogen peroxide). They were exposed 1-5 min to each light. Each experiment was repeated 3 times for each strain of bacteria. Data were analyzed by two-ways ANOVA and least significant difference post-hoc tests. P < 0.05 was considered as significant. After 4 days the colonies were counted.

Results:

Viability of P. gingivalis was reduced 10% and 20% subsequent to exposure to visible light and diode laser, respectively. The values were 65% and 75% for F. nucleatum in a period of 5-min, respectively. Exposure to visible light or laser beam in conjugation with the photosensitizers suspension caused significant reduction in the number of P. gingivalis in duration of 5-min, suggesting a synergic phototoxic effect. However, the survival rate of F. nucleatum following the exposure to laser with hydrogen peroxide, erythrosine and rhizome of Curcuma longa (curcumin) after 5-min was 10%, 20% and 90% respectively.

Conclusion:

Within the limitations of this study, the synergic phototoxic effect of visible light in combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on F. nucleatum was not shown.

Bactericidal effect of visible light in the presence of erythrosine on Porphyromonas gingivalis and Fusobacterium nucleatum compared with diode laser, an in vitro study

OBJECTIVES

Recently, photodynamic therapy (PDT) has been introduced as a new modality in oral bacterial decontamination. Besides, the ability of laser irradiation in the presence of photosensitizing agent to lethal effect on oral bacteria is well documented. Current research aims to evaluate the effect of photodynamic killing of visible blue light in the presence of plaque disclosing agent erythrosine as photosensitizer on Porphyromonas gingivalis associated with periodontal bone loss and Fusobacterium nucleatum associated with soft tissue inflammation, comparing with the near-infrared diode laser.

MATERIALS AND METHODS

Standard suspension of P. gingivalis and F. nucleatum were exposed to Light Emitting Diode (LED) (440-480 nm) used to photopolymerize composite resine dental restoration in combination with erythrosine (22 µm) up to 5 minutes. Bacterial sample were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. Bacterial samples from each treatment groups (radiation-only group, erythrosine-only group and light or laser with erythrosine group) were subcultured onto the surface of agar plates. Survival of these bacteria was determined by counting the number of colony forming units (CFU) after incubation.

RESULTS

Exposure to visible blue light and diode laser in conjugation with erythrosine significantly reduced both species examined viability, whereas erythrosine-treated samples exposed to visible light suggested a statically meaningful differences comparing to diode laser. In addition, bactericidal effect of visible light or diode laser alone on P. gingivalis as black-pigmented bacteria possess endogenous porphyrins was noticeably.

CONCLUSION

Our result suggested that visible blue light source in the presence of plaque disclosing agent erythrosine could can be consider as potential approach of PDT to kill the main gram-negative periodontal pathogens. From a clinical standpoint, this regimen could be established as an additional minimally invasive antibacterial treatment of plaque induced periodontal pathologies.

Singlet oxygen production by Peptide-coated quantum dot-photosensitizer conjugates

Peptide-coated quantum dot-photosensitizer conjugates were developed using novel covalent conjugation strategies on peptides which overcoat quantum dots (QDs). Rose bengal and chlorin e6, photosensitizers (PSs) that generate singlet oxygen in high yield, were covalently attached to phytochelatin-related peptides. The photosensitizer-peptide conjugates were subsequently used to overcoat green- and red-emitting CdSe/CdS/ZnS nanocrystals. Generation of singlet oxygen could be achieved via indirect excitation through Förster (fluorescence) resonance energy transfer (FRET) from the nanocrystals to PSs, or by direct excitation of the PSs. In the latter case, by using two color excitations, the conjugate could be simultaneously used for fluorescence imaging and singlet oxygen generation. Singlet oxygen quantum yields as high as 0.31 were achieved using 532-nm excitation wavelengths.

Site-directed photoproteolysis of 8-oxoguanine DNA glycosylase 1 (OGG1) by specific porphyrin-protein probe conjugates: a strategy to improve the effectiveness of photodynamic therapy for cancer

The specific light-induced, non-enzymatic photolysis of mOGG1 by porphyrin-conjugated or rose bengal-conjugated streptavidin and porphyrin-conjugated or rose bengal-conjugated first specific or secondary anti-IgG antibodies is reported. The porphyrin chlorin e6 and rose bengal were conjugated to either streptavidin, rabbit anti-mOGG1 primary specific antibody fractions or goat anti-rabbit IgG secondary antibody fractions. Under our experimental conditions, visible light of wavelengths greater than 600 nm induced the non-enzymatic degradation of mOGG1 when this DNA repair enzyme either directly formed a complex with chlorin e6-conjugated anti-mOGG1 primary specific antibodies or indirectly formed complexes with either streptavidin-chlorin e6 conjugates and biotinylated first specific anti-mOGG1 antibodies or first specific anti-mOGG1 antibodies and chlorin e6-conjugated anti-rabbit IgG secondary antibodies. Similar results were obtained when rose bengal was used as photosensitizer instead of chlorin e6. The rate of the photochemical reaction of mOGG1 site-directed by all three chlorin e6 antibody complexes was not affected by the presence of the singlet oxygen scavenger sodium azide. Site-directed photoactivatable probes having the capacity to generate reactive oxygen species (ROS) while destroying the DNA repair system in malignant cells and tumors may represent a powerful strategy to boost selectivity, penetration and efficacy of current photodynamic (PDT) therapy methodologies.

Erythrosine is a potential photosensitizer for the photodynamic therapy of oral plaque biofilms

OBJECTIVES

The purpose of this study was to evaluate the clinical plaque disclosing agent erythrosine as a photosensitizer in the photodynamic killing of the oral bacterium Streptococcus mutans grown as a biofilm.

METHODS

S. mutans biofilms of 200 microm thickness were grown in a constant-depth film fermenter. In addition to determining localization of the photosensitizer within biofilms using confocal laser scanning microscopy (CLSM), we compared the bacterial killing efficacy of erythrosine with that of two well-characterized photosensitizers, methylene blue (MB) and photofrin. Incubations were carried out with each photosensitizer (22 microM), and irradiation was for 15 min using a 400 W white light source.

RESULTS

The CLSM results showed that erythrosine is taken up into S. mutans biofilms, where it is associated with the biomass of the biofilm rather than the fluid-filled channels and voids. Comparison of the cell killing efficacy of erythrosine in S. mutans biofilms of different ages showed that erythrosine was 1-2 log(10) more effective at killing biofilm bacteria than photofrin and 0.5-1 log(10) more effective than MB. The results were statistically significant (P < 0.01). Photodynamic therapy (PDT) with all three photosensitizers was increasingly effective as biofilm age increased, suggesting that temporal changes in biofilm architecture and composition affect susceptibility to PDT.

CONCLUSIONS

PDT using erythrosine as photosensitizer shows excellent potential as a treatment for oral plaque biofilms.

The murine DNA glycosylase NEIL2 (mNEIL2) and human DNA polymerase beta bind microtubules in situ and in vitro

8-oxoguanine DNA glycosylase (OGG1), a major DNA repair enzyme in mammalian cells and a component of the base excision repair (BER) pathway, was recently shown to be associated with the microtubule network and the centriole at interphase and the spindle assembly at mitosis. In this study, we determined whether other participants in the BER pathway also bind microtubules in situ and in vitro. Purified recombinant human DNA polymerase beta (DNA Pol beta) and purified recombinant mNEIL2 were chemically conjugated to fluorochromes and photosensitive dyes and used in in situ localization and binding experiments. Results from in situ localization, microtubule co-precipitation and site-directed photochemical experiments showed that recombinant human DNA Pol beta and recombinant mNEIL2 associated with microtubules in situ and in vitro in a manner similar to that shown earlier for another BER pathway component, OGG1. Observations reported in this study suggest that these BER pathway components are microtubule-associated proteins (MAPs) themselves or utilize yet to be identified MAPs to bind microtubules in order to regulate their intracellular trafficking and activities during the cell cycle.

Cell cycle regulation of the murine 8-oxoguanine DNA glycosylase (mOGG1): mOGG1 associates with microtubules during interphase and mitosis

8-Oxoguanine DNA glycosylase (OGG1) is a major DNA repair enzyme in mammalian cells. OGG1 participates in the repair of 8-oxoG, the most abundant known DNA lesion induced by endogenous reactive oxygen species in aerobic organisms. In this study, antibodies directed against purified recombinant human OGG1 (hOGG1) or murine (mOGG1) protein were chemically conjugated to either the photosensitizer Rose Bengal or the fluorescent dye Texas red. These dye-protein conjugates, in combination with binding assays, were used to identify associations between mOGG1 and the cytoskeleton of NIH3T3 fibroblasts. Results from these binding studies showed that mOGG1 associates with the cytoskeleton by specifically binding to the centriole and microtubules radiating from the centrosome at interphase and the spindle assembly at mitosis. Similar results were obtained with hOGG1. Together results reported in this study suggest that OGG1 is a microtubule-associated protein itself or that OGG1 utilizes yet to be identified motor proteins to ride on microtubules as tracks facilitating the movement and redistribution of cytoplasmic OGG1 pools during interphase and mitosis and in response to oxidative DNA damage.

Immunofluorescent localization of the murine 8-oxoguanine DNA glycosylase (mOGG1) in cells growing under normal and nutrient deprivation conditions

OGG1 is a major DNA glycosylase in mammalian cells, participating in the repair of 7,8-dihydro-8-oxoguanine (8-oxoguanine, 8-oxoG), the most abundant known DNA lesion induced by endogenous reactive oxygen species in aerobic organisms. 8-oxoG is therefore often used as a marker for oxidative DNA damage. In this study, polyclonal and monoclonal antibodies were raised against the purified wild-type recombinant murine 8-oxoG DNA glycosylase (mOGG1) protein and their specificity against the native enzyme and the SDS-denatured mOGG1 polypeptide were characterized. Specific antibodies directed against the purified wild-type recombinant mOGG1 were used to localize in situ this DNA repair enzyme in established cell lines (HeLa cells, NIH3T3 fibroblasts) as well as in primary culture mouse embryo fibroblasts growing under either normal or oxidative stress conditions. Results from these studies showed that mOGG1 is localized to the nucleus and the cytoplasm of mammalian cells in culture. However, mOGG1 levels increase and primarily redistribute to the nucleus and its peripheral cytoplasm in cells exposed to oxidative stress conditions. Immunofluorescent localization results reported in this study suggest that susceptibility to oxidative DNA damage varies among mammalian tissue culture cells and that mOGG1 appears to redistribute once mOGG1 cell copy number increases in response to oxidative DNA damage.

Site-directed photochemical disruption of the actin cytoskeleton by actin-binding Rose Bengal-conjugates

The in situ light-induced, non-enzymatic digestion of cytoskeletal actin by a xanthene dye conjugated to heavy meromyosin, anti-actin antibodies and/or anti-myosin antibodies is reported. The dye Rose Bengal was conjugated to either anti-actin antibodies, anti-myosin antibodies or heavy meromyosin. Under our experimental conditions, visible light induced the non-enzymatic breakdown of cytoskeletal actin when mammalian tissue culture cells were probed either with Rose Bengal-conjugated anti-actin and/or anti-myosin antibodies. Similar results were obtained when tissue culture cells were probed with Rose Bengal-conjugated heavy meromyosin before irradiation with visible light. The in situ photochemical reaction depended on the presence of actin-binding Rose Bengal-conjugates.