Translational biophotonics with Raman imaging: clinical applications and beyond

Determining topical product bioequivalence with stimulated Raman scattering microscopy

Generic drugs are essential for affordable medicine and improving accessibility to treatments. Bioequivalence (BE) is typically demonstrated by assessing a generic product's pharmacokinetics (PK) relative to a reference-listed drug (RLD). Accurately estimating cutaneous PK (cPK) at or near the site of action can be challenging for locally acting topical products. Certain cPK approaches are available for assessing local bioavailability (BA) in the skin. Stimulated Raman scattering (SRS) microscopy has unique capabilities enabling continuous, high spatial and temporal resolution and quantitative imaging of drugs within the skin. In this paper, we developed an approach based on SRS and a polymer-based standard reference for the evaluation of topical product BA and BE in human skin ex vivo. BE assessment of tazarotene-containing formulations was achieved using cPK parameters obtained within different skin microstructures. The establishment of BE between the RLD and an approved generic product was successfully demonstrated. Interestingly, within the constraints of the current study design the results suggest similar BA between the tested gel formulation and the reference cream formulation, despite the differences in the formulation/dosage form. Another formulation containing polyethylene glycol as the vehicle was demonstrated to be not bioequivalent to the RLD. Compared to using the SRS approach without a standard reference, the developed approach enabled more consistent and reproducible results, which is crucial in BE assessment. The abundant information from the developed approach can help to systematically identify key areas of study design that will enable a better comparison of topical products and support an assessment of BE.

Current Trends of Raman Spectroscopy in Clinic Settings: Opportunities and Challenges

Early clinical diagnosis, effective intraoperative guidance, and an accurate prognosis can lead to timely and effective medical treatment. The current conventional clinical methods have several limitations. Therefore, there is a need to develop faster and more reliable clinical detection, treatment, and monitoring methods to enhance their clinical applications. Raman spectroscopy is noninvasive and provides highly specific information about the molecular structure and biochemical composition of analytes in a rapid and accurate manner. It has a wide range of applications in biomedicine, materials, and clinical settings. This review primarily focuses on the application of Raman spectroscopy in clinical medicine. The advantages and limitations of Raman spectroscopy over traditional clinical methods are discussed. In addition, the advantages of combining Raman spectroscopy with machine learning, nanoparticles, and probes are demonstrated, thereby extending its applicability to different clinical phases. Examples of the clinical applications of Raman spectroscopy over the last 3 years are also integrated. Finally, various prospective approaches based on Raman spectroscopy in clinical studies are surveyed, and current challenges are discussed.

Ammonia Toxicity and Associated Protein Oxidation: A Single-Cell Surface Enhanced Raman Spectroscopy Study

Ammonia (NH3) is a commonly used industrial chemical to which exposure at high concentrations can result in severe skin damage. Moreover, high levels of ammonia in the human body can lead to hyperammonemia conditions and enhanced cancer metabolism. In this work, the toxicity mechanism of NH3 has been studied against human dermal fibroblast (HDF) cells using surface-enhanced Raman spectroscopy (SERS). For this purpose, gold nanoparticles of size 50 nm have been prepared and used as probes for Raman signal enhancement, after being internalized inside HDF cells. Following the exposure to ammonia, HDF cells showed a significant variation in the protein ternary structure's signals, demonstrating their denaturation and oxidation process, together with early signs of apoptosis. Meaningful changes were observed especially in the Raman vibrations of sulfur-containing amino acids (cysteine and methionine) together with aromatic residues. Fluorescence microscopy revealed the formation of reactive oxygen and nitrogen species in cells, which confirmed their stressed condition and to whom the causes of protein degradation can be attributed. These findings can provide new insights into the mechanism of ammonia toxicity and protein oxidation at a single-cell level, demonstrating the high potential of the SERS technique in investigating the cellular response to toxic compounds.

Quantifying Inflammatory Response and Drug-Aided Resolution in an Atopic Dermatitis model with Deep Learning

Noninvasive quantification of dermal diseases aids efficacy studies and paves the way for broader enrollment in clinical studies across varied demographics. Related to atopic dermatitis, accurate quantification of the onset and resolution of inflammatory flare-ups in the skin remains challenging, as the commonly used macroscale cues do not necessarily represent the underlying inflammation at the cellular level. Although atopic dermatitis affects over 10% of Americans, the genetic underpinnings and cellular level phenomena causing the physical manifestation of the disease require more clarity. Current gold standards of quantification are often invasive, requiring biopsies followed by laboratory analysis. This represents a gap in our ability to diagnose and study skin inflammatory disease, as well as develop improved topical therapeutic treatments. This need can be addressed through noninvasive imaging methods and the use of modern quantitative approaches to streamline the generation of relevant insights. This work reports the nonin- vasive image-based quantification of inflammation in an atopic dermatitis mouse model based on cellular-level deep learning analysis of coherent anti-Stokes Raman scattering and stimulated Raman scattering imaging. This quantifica- tion method allows for timepoint-specific disease scores using morphological and physiological measurements. The outcomes we demonstrate set the stage for applying this workflow to future clinical studies.

Cancer Targeting and Diagnosis: Recent Trends with Carbon Nanotubes

Cancer belongs to a category of disorders characterized by uncontrolled cell development with the potential to invade other bodily organs, resulting in an estimated 10 million deaths globally in 2020. With advancements in nanotechnology-based systems, biomedical applications of nanomaterials are attracting increasing interest as prospective vehicles for targeted cancer therapy and enhancing treatment results. In this context, carbon nanotubes (CNTs) have recently garnered a great deal of interest in the field of cancer diagnosis and treatment due to various factors such as biocompatibility, thermodynamic properties, and varied functionalization. In the present review, we will discuss recent advancements regarding CNT contributions to cancer diagnosis and therapy. Various sensing strategies like electrochemical, colorimetric, plasmonic, and immunosensing are discussed in detail. In the next section, therapy techniques like photothermal therapy, photodynamic therapy, drug targeting, gene therapy, and immunotherapy are also explained in-depth. The toxicological aspect of CNTs for biomedical application will also be discussed in order to ensure the safe real-life and clinical use of CNTs.

Raman Spectroscopy in Prostate Cancer: Techniques, Applications and Advancements

Optical techniques are widely used tools in the visualisation of biological species within complex matrices, including biopsies, tissue resections and biofluids. Raman spectroscopy is an emerging analytical approach that probes the molecular signature of endogenous cellular biomolecules under biocompatible conditions with high spatial resolution. Applications of Raman spectroscopy in prostate cancer include biopsy analysis, assessment of surgical margins and monitoring of treatment efficacy. The advent of advanced Raman imaging techniques, such as stimulated Raman scattering, is creating opportunities for real-time in situ evaluation of prostate cancer. This review provides a focus on the recent preclinical and clinical achievements in implementing Raman-based techniques, highlighting remaining challenges for clinical applications. The research and clinical results achieved through in vivo and ex vivo Raman spectroscopy illustrate areas where these evolving technologies can be best translated into clinical practice.