Development and application of LED arrays for use in phototherapy research

Abstract

Lasers/LEDs demonstrate therapeutic effects for a range of biomedical applications. However, a consensus on effective light irradiation parameters and efficient and reliable measurement techniques remain limited. The objective here is to develop, characterise and demonstrate the application of LED arrays in order to progress and improve the effectiveness and accuracy of in vitro photobiomodulation studies. 96-well plate format LED arrays (400-850 nm) were developed and characterised to accurately assess irradiance delivery to cell cultures. Human dental pulp cells (DPCs) were irradiated (3.5-142 mW/cm : 15-120 s) and the biological responses were assessed using MTT assays. Array calibration was confirmed using a range of optical and analytical techniques. Multivariate analysis of variance revealed biological responses were dependent on wavelength, exposure time and the post-exposure assay time (P < 0.05). Increased MTT asbsorbance was measured 24 h post-irradiation for 30 s exposures of 3.5 mW/cm at 470, 527, 631, 655, 680, 777, 798 and 826 nm with distinct peaks at 631 nm and 798 nm (P < 0.05). Similar wavelengths were also effective at higher irradiances (48-142 mW/cm ). LED arrays and high throughput assays provide a robust and reliable platform to rapidly identify irradiation parameters which is both time- and cost-effective. These arrrays are applicable in photobiomodulation, photodynamic therapy and other photobiomedical research.

Differential responses of myoblasts and myotubes to photobiomodulation are associated with mitochondrial number

“…A mask constructed from silicon was designed to surround each well of the plate, preventing bleed between wells to ensure only a single wavelength of light would impact the biological response in each well‐culture. Spectral characterisation undertaken to confirm wavelength and spectral irradiance values were consistent with those used in previous studies employing different plate formats . Data indicated the array employed for in vitro studies emitted wavelengths ranging from 400 to 830 nm (Figure A) and an average irradiance of 23.05 mW/cm 2 (Figure B).…”

“…In this particular experimental setup, the LED array was designed to enable alignment of LEDs with the plate directly above at a specific irradiance value. As described by Hadis et al that whilst there is variability in the homogeneity of each LED, the effects of this have been minimised through ensuring there is no significant difference in the output of a series of parameters including irradiance (mW/cm 2 ) and radiant exposure (J/cm 2 ). However, despite this it will be important to take into account the effects this may have on the biological output of our experiment.…”

“…Absolute irradiance was determined from the integral of the spectral irradiance (380‐880 nm). Further detail outlining spectral characterisation methods, light‐emitting diode (LED) array design and selection of wavelengths are described by Hadis et al .…”

“…Following linear, optical and ambient light correction, images were recorded using BeamGage software (Ophir). Detailed experimental procedure has previously been reported by Hadis et al .…”

Designing the Uniform Stochastic Photomatrix Therapeutic Systems

“…Superbright LEDs possess quasi-monochromatic properties, i.e., relatively narrow spectral width of the irradiation range-up to several nanometers, depending on the central wavelength of the light source [14][15][16][17][18][19][20]. In certain medical tasks they could be considered as point laser sources, comparable with small laser diodes.…”