Breast augmentations, commonly performed for aesthetic or medical reasons, often use silicone (PDMS) implants. Some patients develop complications like capsular contracture, where scar tissue forms around the implant. Previously, we used stimulated Raman scattering (SRS) microscopy to detect and quantify silicone in stained capsule tissue, finding a correlation between silicone amount and contracture severity. However, we suspected silicone loss during histological preparation, which includes multiple steps like formalin fixation and paraffin embedding. In this study, we assessed silicone loss by comparing adjacent tissue samples from the same capsule: one prepared conventionally and the other snap-frozen. SRS microscopy revealed that snap-frozen samples had roughly five times more silicone, indicating significant silicone loss during conventional preparation. Thus, measuring silicone in histologically prepared samples likely underestimates PDMS content.

Keratoconus and other corneal ectatic disorders involve the degradation of collagen fibers, which compromises the corneal biomechanical properties. UVA crosslinking has emerged as the primary treatment to slow down collagen degradation. This treatment is limited in both penetration depth and spatial precision, potentially leading to unwanted side effects. This work compares the changes in stiffness of corneas crosslinked with UVA irradiation and a near infrared femtosecond laser, using Brillouin microscopy. The stiffness of the crosslinked regions was mapped in terms of Brillouin frequency shift in three dimensions. UVA crosslinking showed an average increase in Brillouin shift of ~ 100 MHz. We demonstrate targeted spatial and axial corneal femtosecond crosslinking, with similar Brillouin shift values to UVA in crosslinked regions.

The image contrast and probing depth of optical methods applied to in vivo skin could be improved by reducing skin scattering using the optical clearing method. The aim of the present study was to quantify, from line-field confocal optical coherence tomography (LC-OCT) 3D images, the modifications of skin scattering properties in vivo during optical clearing. Nine mixtures of optical clearing agents were used in combination with physical and chemical permeation enhancers on human skin of three healthy volunteers. Scattering coefficient and anisotropy factor of the epidermis and the upper dermis were estimated from the 3D LC-OCT images of skin using an exponential decay model of the in-depth intensity profile. We were able to demonstrate a decrease in epidermal scattering (down to 33%)  related to optical clearing with the best results obtained by a mixture of Polyethylene Glycol, Oleic Acid and Propylene Glycol.

This study presents a portable spectroscopic system compatible with ambient light to assess hepatic steatosis (HS) and macrovesicular steatosis (MaS) in human liver specimens. Traditional assessment methods for MaS are limited, prompting the need for non-invasive alternatives. The study utilized a two-stage approach on thawed snap-frozen liver specimens. Biochemical validation compared fat content from Raman and reflectance intensities with triglyceride (TG) quantifications, while histopathological validation contrasted Raman-derived fat content with pathologist evaluations and an algorithm. Analysis of 16 specimens showed a positive correlation between spectroscopic data and TG quantifications. The Raman system differentiated various degrees of global HS and MaS in an additional 66 specimens. A dual-variable prediction algorithm classified significant discrepancies (≥10%) between algorithm-estimated global HS and pathologist-estimated MaS. This study demonstrates the viability of a portable spectroscopic system for non-invasive HS and MaS assessment to enhance real-time donor liver assessments during recovery to improve transplantation outcomes.

The 4T1 tumor model closely approximates the characteristics of human breast cancer and is widely used in laboratory research. Knowledge of the optical parameters of the tumor is important for choosing the correct parameters for laser treatment. In this paper, optical properties and refraction indices of breast tissue in healthy mice and 4T1-model breast tumor have been measured. Using these measurements, absorption coefficient and reduced scattering coefficient have been reconstructed. A significant decrease in both the scattering and refractive index of tumor tissue has been observed. The change in tissue morphology has induced the change in the slope of the scattering spectrum. Thus, the light penetration depth into tumor has increased by almost 1.5-2 times in the NIR “optical windows.” Raman spectra have shown lower lipid content and higher protein content in tumor. The results may be useful for modeling the distribution of laser radiation in healthy tissues and cancers.

Vascular diseases are a leading cause of death and disability worldwide. Despite having precursor conditions like peripheral arterial disease (PAD), they are often only diagnosed after the onset of strokes or heart attacks. Low-cost, portable, non-invasive, point-of-care (POC) assessment of deep vascular function benefits PAD diagnosis, especially in low-and-middle-income countries. Doppler ultrasound-based blood flow measurements can diagnose PAD, albeit, with limited sensitivity and specificity. To overcome this, here, we propose the first-of-its-kind photoacoustic-and-ultrasound (PAUS) imaging system that integrates a multiwavelength pulsed laser diode (PLD) with a compact ultrasound data acquisition system. The portable PLD-PAUS system was validated for deep tissue imaging using tissue phantoms, and for multispectral photoacoustic imaging using an atherosclerosis mimicking phantom. Further, we demonstrated high-contrast volumetric in-vivo photoacoustic imaging of rodent abdominal vasculature and quantified vessel reactivity due to hypercapnia stimulation. The multiparametric functional and molecular imaging capabilities of the PLD-PAUS system holds promise for POC applications.

Spontaneous Raman spectroscopy is a well-established diagnostic tool, allowing for the identification of all Raman active species with a single measurement. Yet, it may suffer from low signal intensity and fluorescent background. In contrast, coherent anti-Stokes Raman scattering (CARS) offers laser-like signals, but the traditional approach lacks the multiplex capability of spontaneous Raman spectroscopy. We present an ultrabroadband CARS setup which aims at exciting the full spectrum (300 - 3700 cm -1) of biological molecules. A dual-output optical parametric amplifier provides a ~7 fs pump/Stokes and a ~ 700 fs probe pulse. CARS spectra of DMSO, ethanol and methanol show great agreement with spontaneous Raman spectroscopy and superiority in fluorescent environments. The spectral resolution proves sufficient to differentiate between the complex spectra of L-proline and hydroxyproline. Moreover, decay constants in the sub picosecond range are determined for individual Raman transitions, providing an additional approach for sample characterization.

The suitability of ultraviolet (UV) radiation for the decontamination of a surgical face mask was studied by comparing experiments with ray-tracing optical simulations. The 3D fiber network was constructed from X-ray tomography images of the layered mask structure consisting of polypropylene fibers. Both simulations and optical measurements on reflection and transmission indicated that UV light was able to penetrate even the deepest material regions. The decontamination experiments, carried out using Staphylococcus aureus and MS2 microbes, indicated an over 6 log 10 reduction in viable virus contamination of the inner filtering layer. This was achieved within two minutes at a moderate dosage level of 0.22 J/cm 2. The simulations show that despite radiation reflection from the outer mask layer, a significant dosage enters the actual filtering layer due to multiple refraction and scattering of UV light from the inner fibers. This leads to an effective decontamination of fibers with small external UV dosage.

Light exposure has been proven to significantly impact human health, and as a result, researchers are increasingly exploring its potential benefits and drawbacks. With the advancements in understanding light and the manufacturing of light sources, modern health lighting has become widely utilized in daily life and plays a critical role in the prevention and treatment of various illnesses. The use of light in healthcare is a global trend, and many countries are actively promoting the development and application of relevant scientific research and medical technology. This field has gained worldwide attention and support from scientists and doctors alike. In this review, we examine the application of lighting in human health and recent breakthroughs in light exposure related to pathology, therapeutic strategies, molecular changes, and more. Finally, we also discuss potential future developments and areas of application.

Aging brain undergoes multiple structural and functional changes. These may contribute to an increased risk of neurodegenerative disease (NDD) and other age-related diseases, highlighting the importance of assessing deviations from healthy brain aging trajectory. In this human brain study, 50 healthy adults were investigated by functional near-infrared spectroscopy (fNIRS). A resting state single channel multiwavelength fNIRS was measured from the forehead in a supine position. The subjects were divided into four age groups. A machine learning approach was utilized for age group classification by using support vector machine and random forest learners with nested cross-validation. The results suggest brain aging effects being more distinct in the oldest age group and a difference in the brain aging for the subjects of the in-between groups. Our study shows high potential for the use of fNIRS in the analysis of brain aging.

Composite nanoparticles with a gold core enveloped by cobalt ferrite nanoparticles show potential for enhanced photothermal therapy. Determining the optimal gold-to-cobalt ferrite nanoparticle ratio, dependent on size, is vital for improving treatment efficiency. We address the urgent need for advancing photothermal therapy through utilising combined plasmon-magnetic composites with potential of controlled directional delivery. Our computational modeling and experimental absorption spectra analysis reveal that adjusting the cobalt ferrite nanoparticle content redshifts the plasmon resonance frequency in gold nanoparticles, which is accompanied by increase in the extinction cross-section. As a result, cobalt ferrite nanoparticle absorption dominates. Our experiments on photothermal response in aqueous solutions of composite nanoparticles of various concentrations demonstrate that 100 μg/ml solution yields a significant temperature increase of ~8.2 K and a photothermal conversion efficiency of ~51%. At this concentration, the composite nanoparticles effectively heat the cell culture medium under photothermal conditions, leading to 22% reduction in cell viability.

Gram staining can classify bacterial species into two large groups based on cell wall differences. Our study revealed that within the same Gram group (Gram-positive or Gram-negative), subtle cell wall variations can alter staining outcomes, with the peptidoglycan layer and lipid content significantly influencing this effect. Thus, bacteria within the same group can also be differentiated by their spectra. Using hyperspectral microscopy, we identified six species of intestinal bacteria with 98.1% accuracy. Our study also demonstrated that selecting the right spectral band and background calibration can enhance the model’s robustness and facilitate precise identification of varying sample batches. This method is suitable for analyzing bacterial community pathologies.

Cartilage is frequently used as scaffolds for repairing and reconstructing body surface organs. However, after successful plastic surgery, transplanted cartilage scaffolds often exhibit deformation and absorption over time. To enhance the shapping stability of cartilage scaffolds and improve patients’ satisfaction after reconstructions, we employed the ear folding models in New Zealand rabbit to confirm whether the 1064nm Nd:YAG laser could promote cartilage reshapping. There was an increase in collagen and aromatase (Cyp19) expression within the ear cartilage after laser treatment. Moreover, we have discovered that the Cyp19 inhibitor can suppress the shaping effect of the laser on cartilage, as well as the expression of collagen and Cyp19. The overall findings suggest that treatment with 1064nm Nd:YAG laser irradiation can enhance estrogen levels in local cartilage tissues by upregulating Cyp19 expression in chondrocytes through photobiomodulation, thereby promoting the proliferation and collagen secretion of chondrocytes to improve cartilage reshaping and stability.

Metastatic melanoma is a cancer for which vascularization is not a diagnostic criterion. The aim of this study was to evaluate the applicabilities of laser speckle contrast imaging (LSCI) and contrast enhanced ultrasound (CEUS) in a mouse-model. B16F10 cells were xenografted to C57BL/6 mice. Mice were treated with anti-PD1 or 0.9% NaCl and tumor volume was measured daily. CEUS and LSCI were performed weekly. No difference in tumor growth or median survival were observed between treated and no-treaated mice. No significant difference in tumor volume measurement comparing caliper and CEUS was observed. LSCI and CEUS analyses showed a decrease in tumor perfusion in both groups of mice. Although both CEUS and LSCI are useful for measuring tumor volume, LSCI appears to be more robust and effective for monitoring tumor microcirculation. Non-invasive investigations are needed to better predict tumor vascularization: CEUS and LSCI have a good applicability in a mice model.

A novel composite wound dressing hydrogel by incorporating single-walled carbon nanotubes and indocyanine green into a dual-crosslinked hydrogel through Schiff base reaction was developed. The objective was to prevent wound infection and enhance the thermal effect induced by laser energy. The hydrogel matrix was constructed using oxidized gelatin, pre-crosslinked with calcium ions, along with carboxymethyl chitosan, crosslinked via Schiff base reaction. Optimization of the blank hydrogel’s gelation time, swelling index, degradation rate, and mechanical properties was achieved by adding 0.1% SWCNT and 0.1% ICG. Among them, the SWCNT-loaded hydrogel BCG-SWCNT exhibited superior performance overall: a gelation time of 102 seconds; a swelling index above 30 after equilibrium swelling; a degradation rate of 100.5% on the seventh day; and a compressive modulus of 8.8 KPa. It displayed significant inhibition against methicillin-resistant Staphylococcus aureus infection in wounds. When combined with laser energy usage, the composite hydrogel demonstrated excellent pro-healing activity in rats.

5-Aminolevulinic (5-ALA) acid photodynamic therapy (PDT) is a treatment for actinic keratosis and has been studied as a treatment for non-invasive cutaneous squamous cell carcinoma (cSCC). PDT induces apoptosis and necrosis in actinic keratosis and cSCC. 5-ALA blue light PDT may modulate gene expression and pathways in surviving cells. In this study, differential gene expression and pathway analysis of cSCC and human dermal fibroblasts were compared before and after 5-ALA blue light PDT using RNA-Sequencing. No genes were differentially expressed after correcting for multiple testing (FDR <0.05). As a result, transcription factor, gene enrichment, and pathway analysis were performed with genes identified before multiple testing (p<0.05). Pathways associated with proliferation and carcinogenesis were downregulated. These findings using 5-ALA blue light PDT are similar to previously published studies using methyl-aminolevulinic and red light protocols, indicating that surviving residual cells may undergo changes consistent with a less aggressive cancerous phenotype.

We demonstrate an automated two-step tumor segmentation method leveraging color information from brightfield images of fresh core needle biopsies of breast tissue. Three different color spaces (HSV, CIELAB, YCbCr) were explored for the segmentation task. By leveraging white-light and green-light images, we identified two different types of color transformations that could separate adipose from benign and tumor or cancerous tissue. We leveraged these two distinct color transformation methods in a two-step process where adipose tissue segmentation was followed by benign tissue segmentation thereby isolating the malignant region of the biopsy. Our tumor segmentation algorithm and imaging probe could highlight suspicious regions on unprocessed biopsy tissue to guide selection of areas most similar to malignant tissues for tissue pathology whether it be formalin fixed or frozen sections, expedite tissue selection for molecular testing, detect positive tumor margins, or serve an alternative to tissue pathology, in countries where these services are lacking.