This PDF file contains the front matters associated with SPIE Proceedings Volume 12377, including the Title Page, Copyright information, Table of Contents and Conference Committee lists.

The detection of human immunodeficiency virus (HIV) at the point of care (POC) remains one of the most valuable advances in the healthcare. To enrich and broaden POC technologies for viral diagnosis, several technologies have been developed for virus detection utilizing electrical, optical, and acoustic sensing methods such as surface plasmon resonance (SPR), localized surface plasmon resonance (LSPR), quartz crystal microbalance (QCM), nanowires and impedance analysis. Among these approaches, photonic crystal biosensors offer a rapid and sensitive optical detection method for biomolecules, cells, and viruses by monitoring the dielectric permittivity changes at the interface of a transducer substrate and the analyte. Photonic crystals (PCs) are macroporous materials that possess a periodically modulated dielectric constant, with the properties of confining and controlling the propagation of light owing to the existence of photonic band gap, a band of frequencies in which light propagation in the photonic crystal is forbidden. The capabilities of photonic crystals have a potential to meet the growing demand of simplified and improved point of care HIV diagnostics tools without compromising quality of patient care. This work focuses on examining the biosensing capabilities of a photonic crystal-based platform that can capture HIV in the presence of HIV antibodies. The preliminary data revealed that HIV was detected on the photonic crystal-based platform. These findings demonstrate that photonic-crystal based technologies are eligible devices to be used for point of care detection of viral infections. Further work is still required to determine its specificity as well as its capabilities for quantitative analysis, where it can be used for viral load measurements.

Delivering therapeutic drug molecules to the target site and releasing the cargo site-specifically is of major interest in biomedicine. To carry and release drugs to specific target tissues, different nanotechnology approaches have been utilized. These include light-sensitive liposomal carriers, which have been engineered to release cargo from their aqueous cores when illuminated by certain wavelengths of laser light. To study drug release parameters in vitro, Modulight has designed and automated biomedical illumination system ML8500. ML8500 can be tailored to house up to eight Modulight semiconductor lasers ranging from 400nm-2000nm selected based on the optical properties of dyes and molecules of interest. The illumination system can be configured for different well plate types and includes environmental control of temperature and CO2 to provide stable conditions for the studied cell types. Utilizing the ML8500 illumination system, the safety of laser light illumination for the liposomal drug delivery was investigated in retinal pigment epithelial (ARPE-19) cell line.

Lasers with ultrashort pulse durations have become ubiquitous in a variety of applications, including medical procedures such as laser eye surgery. These sources generate high peak powers such that the role of nonlinear optical effects resulting from the interaction of femtosecond pulses with the surrounding media needs to be considered when evaluating their potential hazard to the eye. In the latest version of the ANSI laser safety standards, the safe exposure limits have been relaxed at wavelengths between 1.2 – 1.4 µm because of biological data collected for the nanosecond and millisecond pulse regimes. However, this increase did not consider nonlinear optical effects resulting from the interaction with femtosecond pulses. One manifestation of these nonlinear effects is the generation of broadband light known as supercontinuum. We sent a near infrared (NIR) femtosecond laser with peak energies at or below the energy corresponding to the maximum permissible exposure (MPE) limit listed in laser safety standards into the eye of anesthetized porcine subjects. Exposures were performed with both collimated and converging beams to simulate an eye focused at a far distance and one focused at a near distance, respectively, and have the potential to generate a supercontinuum within the eye. Nominally 1 h and 24 h after exposure, the retina was examined using a fundus camera. The presence or absence of any alteration of the retina was noted. The results of this study inform the laser safety standards committees about potential hazards to the eye due to the supercontinuum generated by nonlinear effects in the aqueous media of the eye.

Accurate values of the optical properties of skin and subcutaneous fat are important for a variety of applications, such as optical imaging techniques and computational modeling of possible hazardous laser exposure. Several studies are available in the published literature that report skin optical properties, but the method of tissue preparation and storage in these experiments can be variable. These methods include the application of some form of cold storage, such as refrigeration or freezing, which may in turn affect the optical properties of the tissues compared to the in vivo or freshly excised case. We measured the absorption and scattering coefficients of skin and subcutaneous fat samples prior to and following various methods of cold storage, particularly refrigeration, slow freezing, and flash freezing. Tissues were collected from two subjects in order to capture biological variability. We employed a double integrating sphere setup and the inverse adding-doubling method to determine optical properties. The results of this investigation will help contextualize existing studies on tissue optical properties and enable informed procedural design for future measurements.

We report a single-cell level resolution (≤10 µm), laser desorption-based mass spectrometry imaging platform. An optical parametric amplifier is used to generate ∼100 ps, 200 nJ pulses at around 3 µm with a maximum repetition rate of 500 kHz. The pulses are tightly focussed on to fresh frozen animal tissue samples with a thickness of 10 µm. Small volumes of tissue are readily ablated by the laser and are subsequently chemically analyzed using a Rapid Evaporative Ionization Mass Spectrometry (REIMS) source installed on a time of flight mass analyzer. Raster scanning the samples through the laser focus enables the acquisition of mass spectrometry data which can be processed into images with pixel size 10 µm without oversampling, corresponding to cellular level resolution.

The treatment effect of pigmented lesions with picosecond and nanosecond lasers is produced mainly from optical absorption by melanosomes. Differences in the treatment effect have been evaluated based on the linear absorption of local fluence. However, nonlinear absorption by melanin inside melanosomes occurs during short-pulsed laser propagation in skin tissue owing to the high-power density. Our previous study demonstrated that a nonlinear absorption model based on sequential two-photon absorption and nonradiative decays was validated to describe nonlinear absorption by melanin. In this study, we comparatively evaluate light distributions in skin tissue with pigmented lesions irradiated with short-pulsed lasers using a Monte Carlo model combined with the nonlinear absorption model. Light distributions in a numerical model of human skin tissue with epidermal pigmented lesions were calculated for a single shot of 450-ps and 10-ns laser pulses at a wavelength of 532 nm, a fluence of 1 J/cm2, and a spot size of 3 mm. The computational simulations show that the penetration depth in the skin tissue was shorter for the picosecond laser. The simulation results suggested that picosecond lasers can reduce damage to surrounding tissue compared to nanosecond lasers. Although these results need to be validated by experiments, our simulations will provide a quantitative evaluation of the safety and efficacy of short-pulsed laser treatment of pigmented lesions.

This study aims to optimize the ablation depth using a Ho:YAG laser and a waterjet. The results show that the maximum achieved depth for a 1 cm-long line cut was 0.86, 1.07, and 2.24 mm at energies of 500, 1000, and 2000 mJ/pulse, respectively. The line cuts were performed by translating the sample horizontally (back and forth) at the speed of 8 mm/s. After 120 s (~100 pulses/position), the depth achieved was saturated at all energy levels. As Ho:YAG lasers can be delivered through low-cost and flexible silica fibers, they have a great potential for endoscopic minimally invasive surgeries.

Thermo-mechanical hard tissue ablation with pulsed mid-infrared lasers is an efficient and minimally invasive method for precise bone cutting. The efficiency of the ablation process strongly depends on the absorption of laser radiation in the intracellular water of hard tissue. Therefore, 3 µm laser sources show high efficiency in bone ablation with a small heat affected zone. Until now, it was not possible to transfer this high efficiency into high ablation rates because of the limited repetition rate of commercially available laser sources. In this study, we demonstrate ablation experiments on bovine bone tissue utilizing a novel 3 µm laser source with a repetition rate of 12 kHz and nanosecond pulse duration. We optimized process parameters especially focus position, flow rate of a water spray system and pulse overlap for a fast and non-thermal ablation process. By optimizing the optical system, we were able to realize a fluence for fast bone ablation with rates of up to 2.2 mm3/s and a maximum ablation depth of 3.4 mm. For further increase of the depth-dependent ablation rate, it was possible to estimate required beam caustic and laser specifications.

Heavy metals are one of the important components of water pollution. Heavy metals such as copper, zinc and cobalt are essential for the growth of living organisms as micronutrients. However, copper above critical levels can pose serious problems for the environment and human health. The biospeckle observed in OCT have the potential to map dynamic activities inside the plants. We propose biospeckle optical coherence tomography (bOCT) and demonstrate that the technique can monitor biological activity in plants. In bOCT, the temporal speckle contrast variation of the OCT reflection signal is used as a parameter to characterize the internal activities of the aquatic plant (Myriophyllum). Plant stems were observed using the bOCT technique after 7 days of exposure to copper solutions of three different copper concentrations to 0, 30, 100 mg/l. In addition, statistical Interferometry Technique (SIT) system that is also a very sensitive optical measurement technique developed in our lab. SIT enables the direct observation of short-term displacement or extension / shrinkage of plant surface with precision of nanometer scale and on a time scale of seconds. Compared with the bOCT technique, it takes short time. It does not require 7 days of exposure time. In just 3 hours of experiment time, we observed that the plants were receiving heavy metal stress in the copper solution. Under the same heavy metal exposure conditions (7 days), enzyme activities in plants were also measured and analyzed to demonstrate the reliability of our two laser measurement techniques. It can be seen that the increase of copper solution has a significant effect on the activity of plants. It was not possible to observe the effects of 7 days of heavy metal exposure on plants by measuring their length or the color of their leaves. Compared with traditional bioassay methods, SIT technology is the fastest, followed by bOCT technology. Both technologies are advanced and can be used as a new method for the determination of plant bioactivity.

Statistical Interferometry Technique (SIT) developed in our laboratory is a unique optical interferometry method using the statistical property of a complete randomness of fully developed speckle field. SIT enables non-invasive and real-time measurement of short-time sub-nanometric growth behaviors of plants. Applying SIT to the measurement of plant leaf elongation, we found that plants grow with very small fluctuations at nanometric scale, named as Nanometric Intrinsic Fluctuation (NIF) that formed the basis of our research. Our previous studies have demonstrated that NIF seems to reflect the healthiness of plants sensitively. In other words, SIT could assess an environmental condition through a plant NIF. However, the origin of NIF is still unknown. In this study, we focus on the effect of far-red light (FR) of wavelength 700-800 nm and evaluate how it affects NIF to infer the origin of NIF from the mechanism of FR-induced growth. LED (wavelength of 730 nm) was employed as a FR source, and fresh rice seedlings (2-4 weeks age) were used in the experiment. FR illumination at 50 µmol/m2 /s increased the standard deviation of NIF of rice seedlings approximately 50% within 30 minutes. According to the literatures, FR increase endogenous auxin level via phytochrome signaling, and auxin-induced growth may occur within a few tens of minutes. In addition, it was found in our previous study that low concentration of exogenous auxin increases the magnitude of NIF. Hence, these results implies that not only FR has a positive effect on plant growth but also the increase may be caused by auxin-induced growth.

While artificial cultivation is gaining prominence due to rapid climate change, lighting costs remain a challenge. Therefore, research is needed to cultivate plants more efficiently. At the same time, it has been found that a mixture of far-red light (FR) and red light (R) also promotes growth through the action of phytochrome, a photoreceptor in the plant body. However, these studies require time and damaging of the plant to measure the dry mass and area of leaves, and immediate effects have not been investigated so far. Therefore, in this study, we propose laser biospeckle to evaluate the relationship between plant growth duration and FR response. Laser biospeckles are formed by light scattered from organelles in plant tissues by laser irradiation. The intensity of these speckles changes with time, and by examining these changes, the activity inside the plant can be evaluated. Biospeckles of arugula leaves were obtained by irradiating the leaves with laser light of wavelength 852 nm and simultaneously with LED light of wavelength 735 nm (FR) and 630 nm (R). Biospeckle movies under FR and non-irradiation were recorded by a CMOS camera at 15 frames/sec for 20 seconds. From the movie, correlation between the first frame and the subsequent frames were calculated. Experimental results showed that arugula at 1-month after seed planting showed an immediate FR response, while those at 3-month showed a sustained response. The relationship between biospeckle movement and plant growth behaviour is under investigation.

In concentrated fluorescent solutions, the reabsorption and reemission of fluorescence light affects the temporal shape of the registered emission on the ps to ns time scale. Time-of-flight spectroscopy and intensity based tomography employ light transport models to characterize scattering of biological tissue providing information on the effective path length of the photons and the origin of emission. We propose the evaluation of fluorescence decay curves after reabsorption events to i) determine correction factors for time resolved fluorescence spectroscopy and tomography and ii) to exploit the information in the specific time resolved fluorescence traces to obtain information on the depth of signal generation in tissue and/or determination of reabsorbing structures as for example dye loaded micelles and cell compartments. The expected fluorescence decay curves after reabsorption events were modelled with rate equations for reabsorption and reemission. The fluorescence traces were fitted with the developed model in dependency of fluorophore concentration and path length. The results indicate that reabsorption can be quantitatively determined and depth information can be reconstructed from the time-course of the fluorescence signal. The applicability of the proposed technique to time-resolved fluorescence tomography is discussed.

Among the deadliest diseases in human history, Alzheimer's disease (AD) is a chronic neurodegenerative disorder that increases in seriousness over time. Changes in the brain start several decades before the development of AD, as an abnormal protein, beta-amyloid, start aggregating in the hippocampus area of the brain. At an early stage of AD, structural changes occur at the nanoscale level due to intracellular structural alterations. Hence, detecting nanoscale-level abnormalities early in the disease process is crucial for effective treatment. Dual optical/photonic techniques, Partial wave spectroscopy (PWS), and inverse participation ratio (IPR), are used to detect the nano to submicron scales structural alterations in the human brain cells/tissues due to AD.

Recently, the pollution caused by various hazardous chemicals has become a very serious problem. Currently, 200 million kinds of chemical substances are registered, and it is technically and costly very difficult or even impossible to analyse, identify each chemical individually and then evaluate their toxicity on the environment. On the other hand, bioassay has been getting a lot of attention where the toxicity of environmental toxicity is assessed based on the reaction of micro-organisms such as plankton without identifying each chemical individually. For this technique, a microscope observation is required to obtain critical features such as alive/dead status and swimming ability. With smaller microorganisms, microscope observation becomes more difficult due to the narrower focal depth of the imaging system. In our study, to overcome these difficulties, we proposed a novel technique for the micro-bioassay utilizing laser biospeckle in the diffraction field generated from plankton. Paramecium chilomonas of size 30-40 µm was exposed to different pH conditions from control 7.2 to gradually decreasing by 0.5 till 3.7. Results reveal the sensitivity of laser biospeckles in detecting the subtle changes in the swimming behavior, the health of the microbe with change in pH suggesting the potential for fast assessment the toxicity of an environment.

Parkinson's disease (PD) is a progressive neurodegenerative disorder, characterized by degeneration of dopaminergic neurons in the substantia nigra of the midbrain and loss of both motor and non-motor features. We apply photonics techniques for the characterization of structural changes in brain cells/tissues in progressive PD. In particular, we use mesoscopic optical physics-based finer-focused partial wave spectroscopy (PWS) technique to quantify the nano to submicron scales structural alterations in the brain tissues. Initial results show a change in structural disorder (Ld) as well as in the nuclear DNA spatial mass density in brain tissues of PD patients due to density fluctuations.

SARS-CoV-2 is a new threat to public health due to its increased transmissibility and immune evasion. Angiotensin converting enzyme 2 (ACE2) plays a critical role in SARS-CoV-2 infection as its serve as the virus's major entry receptor in humans. Vaccines have been authorized for emergency use to control the current pandemic and they have greatly reduced the spread of SARS-CoV-2 and mortality rates, nevertheless this coronavirus has shown the ability to endure crucial mutations that increases its infectivity which makes it likely that the virus will continue to mutate and disseminate. There is a need to find and introduce alternative and effective methods of controlling SARS-CoV-2. Notably, low-level laser therapy (LLLT) is a method of exposing cells or tissue to low levels of red and near infrared light which has a high success rate for treatment of other ailments. The aim of the study is to determine for the first time, the effects of LLLT on SARS-CoV-2 infected HEK293/ACE2 cells and compare them to uninfected ones. Both infected and uninfected HEK293/ACE2 cells were irradiated at a wavelength of 640 nm, at different doses. Then, the effects of laser irradiation on the cells and the virus were evaluated using luciferase, cytotoxicity, and cell viability assays. Preliminary results showed that irradiated uninfected cells had no changes in cell viability and cytotoxicity, while there were changes in irradiated infected cells. In addition, laser irradiation caused cell membrane damage in infected cells. Lastly, uninfected irradiated cells showed no luciferase activity while laser irradiation reduced luciferase activity in infected cells.