Exposure of 3T3 mouse Fibroblasts and Collagen to High Intensity Blue Light

Potentiation of Antimicrobial Photodynamic Therapy by Curcumin Loaded Graphene Quantum Dots

Increasing resistance to existing antibiotics by microbes is currently the biggest dilemma. Antimicrobial photodynamic therapy is a promising alternative for treatment of multidrug resistant infections. The aim of current study was to fabricate graphene quantum dots loaded with curcumin as photosensitizer for improved antimicrobial photodynamic therapy. The study involved fabrication of blank and curcumin-loaded graphene quantum dots, their characterizations (TEM, UV-visible & fluorescence emission spectra), cytotoxicity assay, ROS assay and investigation of enhanced antimicrobial photodynamic effect against resistant microbes. The fabrication of blank and loaded graphene quantum dots was confirmed by observation of peak shift and changes in peak intensity of blank graphene quantum dots, curcumin alone compared to curcumin loaded graphene quantum dots in UV-visible and fluoresce emission spectra. Cytotoxicity assay showed that 100 µM concentration was not toxic to NIH/3t3 fibroblasts. In ROS assay, the curcumin loaded formulation showed threefold increase in ROS production. Blue light (405 nm) irradiance of 30 J/cm² and photosensitizer concentration of 100 µM showed ~3.5 log₁₀ enhanced CUF reduction against Pseudomonas aeruginosa, MRSA, Escherichia coli, and Candida albicans. In conclusion, curcumin-loaded graphene quantum dots shoed enhanced antimicrobial photodynamic effects and can be used as an alternative effective treatment for resistant infections.

The viability of human cells irradiated with 470-nm light at various radiant energies in vitro

Blue light is known to be antimicrobial, but its effect on normal cutaneous and subcutaneous cells remains unclear. Therefore, we studied the effect of 470-nm light on the viability of adult and neonatal human dermal fibroblasts, Jurkat T-cells, and THP-1 monocytes in vitro. Each culture was irradiated with 0, 3, 55, or 110 J/cm² of 470-nm light and subjected to trypan blue assay to ascertain viability. Further, MTT, neutral red, and fluorescence assays of fibroblasts were performed, and cell morphology visualized using bright field and fluorescence microscopy. At each dose and in each of the four cell lines, there was no significant difference in cell concentration between irradiated and non-irradiated cultures, even though irradiation with 55 J/cm² or 110 J/cm² slightly decreased cell count. Light microscopy showed progressive morphological changes in the fibroblasts as energy fluence increased from 55 to 110 J/cm². Irradiation at 3 J/cm² produced a slight but non-significant increase in the viability of Jurkat T-cells and THP-1 monocytes. In contrast, at 110 J/cm² radiant exposure, irradiation slightly decreased the viability of all four cells. While 3 J/cm² appears stimulatory, our finding that 110 J/cm² produces a slight decrease in viability and engenders morphological changes in fibroblasts, suggesting that such high doses should be avoided in blue light treatments.

Irradiation with 365 nm and 405 nm wavelength shows differences in DNA damage of swine pancreatic islets

INTRODUCTION

3D printing is being used more extensively in modern biomedicine. One of the problems is selecting a proper crosslinking method of bioprinted material. Amongst currently used techniques we can distinguish: physical crosslinking (e.g. Ca2+ and Sr2+) and chemical crosslinking-the UV light crosslinking causing the biggest discussion. UV radiation is selectively absorbed by DNA, mainly in the UV-B region but also (to some extent) in UV-A and UV-C regions. DNA excitement results in typical photoproducts. The amount of strand breaks may vary depending on the period of exposition, it can also differ when cells undergo incubation after radiation.

AIM

The aim of this study was to show whether and how the time of irradiation with 405 nm and 365 nm wavelengths affect DNA damage in cell lines and micro-organs (pancreatic islets).

MATERIALS AND METHODS

The degree of DNA damage caused by different wavelengths of radiation (405 nm and 365 nm) was evaluated by a comet assay. The test was performed on fibroblasts, alpha cells, beta cells and porcine pancreatic islets after 24 hours incubation period. Samples without radiation treatment were selected as a control group. Results analysis consisted of determining the percent of cells with damaged DNA and the tail intensity evaluation.

RESULTS

The degree of DNA damage in pancreatic islets after exposure to 405 nm wavelength oscillated between 2% and 6% depending on the tested time period (10 - 300 seconds). However, treating islets using 365 nm wavelength resulted in damage up to 50%. This clearly shows significantly less damage when using 405 nm wavelength. Similar results were obtained for the tested cell lines.

CONCLUSIONS

Crosslinking with 405 nm is better for pancreatic islets than crosslinking with 365 nm UV light.

An Introduction to 3D Bioprinting: Possibilities, Challenges and Future Aspects

Bioprinting is an emerging field in regenerative medicine. Producing cell-laden, three-dimensional structures to mimic bodily tissues has an important role not only in tissue engineering, but also in drug delivery and cancer studies. Bioprinting can provide patient-specific spatial geometry, controlled microstructures and the positioning of different cell types for the fabrication of tissue engineering scaffolds. In this brief review, the different fabrication techniques: laser-based, extrusion-based and inkjet-based bioprinting, are defined, elaborated and compared. Advantages and challenges of each technique are addressed as well as the current research status of each technique towards various tissue types. Nozzle-based techniques, like inkjet and extrusion printing, and laser-based techniques, like stereolithography and laser-assisted bioprinting, are all capable of producing successful bioprinted scaffolds. These four techniques were found to have diverse effects on cell viability, resolution and print fidelity. Additionally, the choice of materials and their concentrations were also found to impact the printing characteristics. Each technique has demonstrated individual advantages and disadvantages with more recent research conduct involving multiple techniques to combine the advantages of each technique.

Visible Light Photoinitiation of Cell-Adhesive Gelatin Methacryloyl Hydrogels for Stereolithography 3D Bioprinting

We present the first cell-attachable and visible-light-crosslinkable bioinks based on gelatin methacryloyl (GelMA) with eosin Y (EY) photoinitiation for stereolithography three-dimensional (3D) bioprinting. To develop a visible-light-crosslinkable hydrogel, we systematically studied five combinations of GelMA and EY photoinitiator with various concentrations. Their mechanical properties, microstructures, and cell viability and confluency after encapsulation were investigated rigorously to elucidate the effects of the EY and GelMA macromer concentrations on the characteristics of the hydrogel. Experimental results show that the compressive Young's modulus and pore size are positively affected by the concentration of EY, whereas the mass swelling ratio and cell viability are negatively affected. Increasing the concentration of GelMA helps in improving the compressive Young's modulus and cell attachment. We further employed the developed visible-light-based stereolithography bioprinting system to print the patterned cell-laden hydrogels to demonstrate the bioprinting applications of the developed hydrogel. We observed good cell proliferation and the formation of a 3D cellular network inside the printed pattern at day 5, which proves the great feasibility of using EY-GelMA as the bioinks for biofabrication and tissue engineering.

Efficacy of Pulsed 405-nm Light-Emitting Diodes for Antimicrobial Photodynamic Inactivation: Effects of Intensity, Frequency, and Duty Cycle

Objective: This study investigates possible advantages in pulsed over continuous 405-nm light-emitting diode (LED) light for bacterial inactivation and energy efficiency. Background: Alternative nonantibiotic methods of disinfection and infection control have become of significant interest. Recent studies have demonstrated the application of systems using 405-nm LEDs for continuous disinfection of the clinical environment, and also for potential treatment of contaminated wounds. Methods: Liquid suspensions of 10³ colony-forming units/mL populations of Staphylococcus aureus were subject to pulsed 405-nm light of different frequencies, duty cycles, and intensities and for different lengths of time. Results: Pulsed exposures with the same average irradiance of 16 mW/cm² and varying duty cycle (25%, 50%, 75%) showed very similar performance compared with continuous exposures, with 95–98% reduction of S. aureus achieved for all duty cycles. The pulsing frequency was varied in intervals from 100 Hz to 10 kHz and appeared to have little effect on antimicrobial efficacy. However, when comparing pulsed with continuous exposure, an improvement in inactivation per unit optical energy was achieved, with results showing an increase of approximately 83% in optical efficiency. Conclusions: These results suggest that under pulsed conditions, a lower energy consumption and lower perceived brightness could be achieved, thus potentially providing improved operating conditions for medical/infection control applications without compromising antimicrobial efficacy.