Biology subjects

Robles, F. E.

Publications and source records attributed to Robles, F. E..

4 recordsLinked to original sources

bioRxiv2025

Label-Free, Real-Time, In Vivo Optical Biopsy with a Handheld Quantitative Phase Microscope

In this work we develop and demonstrate the utility of a compact, handheld quantitative phase imaging microscope that enables label-free, in vivo optical imaging of bulk tissues with clear cellular and subcellular histological detail in real-time. The proposed device overcomes significant challenges in optical imaging for in vivo applications, particularly for clinical human use. The approach uses quantitative oblique back illumination microscopy (qOBM) to obtain quantitative phase information of opaque samples using epi-illumination. The compact handheld probe achieves 0.8 {micro}m lateral resolution, 5 {micro}m axial resolution, 300 {micro}m X 300 {micro}m field of view, and operates at 25Hz in a wide-field (non-scanning) configuration, enabling real-time imaging. The probe is also inexpensive and has no moving components, making it robust. The utility of the probe is demonstrated in (1) human skin in vivo, (2) brain tumor tissue ex vivo from a murine tumor model and from discarded human tissue from neurosurgery, and (3) in vivo using healthy brain tissue from a large animal model (swine), simulating neurosurgical conditions. Given the clear cellular and subcellular histological detail (i.e., "optical biopsy") obtained in real-time, combined with the ease-of-use and low-cost of the system, the proposed device has significant implications for a broad range of clinical applications.

bioengineering↗

bioRxiv2025

Single Capture Quantitative Oblique Back-Illumination Microscopy

Quantitative oblique back-illumination microscopy (qOBM) has emerged as a powerful technique for label-free, 3D quantitative phase imaging of arbitrarily thick biological specimens. However, in its initial embodiment, qOBM requires multiple captures for phase recovery, which reduces imaging speed and increases system complexity. In this work, we present a novel advancement in qOBM: single-capture qOBM (SCqOBM) which utilizes a deep learning model to accurately reconstruct phase information from a single oblique back-illumination capture. We demonstrate that SCqOBM achieves remarkable phase imaging accuracy, closely matching the results of traditional four-capture qOBM in diverse biological samples. We first highlight the unique potential of SCqOBM for non-invasive, in-vivo imaging applications by visualizing blood flow in mouse brain and human arm. Additionally, we demonstrate single-slice (en-face) quantitative phase imaging at 2 kHz and volumetric refractive index tomography at speeds up to 10 volumes per second. SCqOBM offers transformative advantages in speed, simplicity, and system accessibility, making it highly suitable for dynamic and real-time imaging applications. Its ability to produce high-resolution, quantitative phase and refractive index images with minimal hardware complexity opens new frontiers in biomedical research and clinical diagnostics, including non-invasive hematological assessments and in-vivo tissue imaging.

bioengineering↗

bioRxiv2025

Non-destructive, high-resolution T cell characterization and subtyping via deep-ultraviolet microscopy

T cell characterization is critical for understanding immune function, monitoring disease progression, and optimizing cell-based therapies. Current technologies to characterize T cells, such as flow cytometry, require fluorescent labeling and typically are destructive endpoint measurements. Non-destructive, label-free imaging methods have been proposed, but face limitations with throughput, specificity, and system complexity. Here we demonstrate deep-ultraviolet (UV) microscopy as a label-free, non-destructive, fast and simple imaging approach for assessing T cell viability, activation state, and subtype with high accuracy. Using static deep-UV images, we characterize T cell viability and activation state, demonstrating excellent agreement with flow cytometry measurements. We further apply dynamic deep-UV imaging to quantify intracellular activity, enabling fast and accurate subtyping of CD4+ and CD8+ T cells. These results corroborate recent studies on metabolic activity differences between these subtypes, but now with deep-UV microscopy they are enabled by a non-destructive, fast, low-cost and simple approach. Together, our results demonstrate deep-UV microscopy as a powerful tool for high-throughput immune cell characterization, with broad applications in immunology re-search, immune monitoring, and development of emerging cell-based therapies.

immunology↗

bioRxiv2025

Label-Free In-Line Characterization of Immune Cell Culture using Quantitative Phase Imaging

Cell therapies, including T cell immunotherapies, offer promising treatments for previously untreatable diseases, but their widespread use is hindered by challenges in monitoring therapeutic cells during culture--impacting consistency, potency, and cost. This work demonstrates the use of quantitative phase imaging (QPI), specifically a compact, non-interferometric form called quantitative oblique back illumination microscopy (qOBM), for non-destructive, label-free, in-line assessment of T cell cultures. qOBM enables near real-time feedback on culture growth, contamination, and cell status (viability and activation), comparable to flow cytometry. We further apply this method to characterize genetically modified CAR T cells and explore its potential for advanced T cell phenotyping. Analysis of data from over 50 independent donors shows strong correlation between qOBM metrics and traditional destructive at-line assays. Overall, qOBM provides a powerful tool for continuous, in-line monitoring of therapeutic cell cultures, which can be transformative for improving reproducibility, reducing costs, and advancing the development of cell-based therapies.

immunology↗