Biology subjects

Revzin, A.

Publications and source records attributed to Revzin, A..

5 recordsLinked to original sources

bioRxiv2025

Integrating microfluidic automation into thermoplastic devices for analysis of small volumes of blood

Microfluidic devices hold considerable promise for miniaturizing and automating laboratory scale workflows involving sample preparation and biomarker analysis. By-and-large microfluidic automation has been implemented using polydimethyl siloxane (PDMS) - a material that presents challenges for scalable manufacturing. In this paper, we fabricated an automated microfluidic device composed of thermoplastic material, poly (methyl methacrylate) (PMMA), and demonstrated a sophisticated workflow consisting of plasma extraction, sample aliquoting and sample-reagent mixing steps performed in the device. Automation was accomplished using multiple on-board microvalves consisting of a pressure sensitive adhesive (PSA) membrane sandwiched between PMMA flow and control layers. In addition to novel microvalves, our device included features designed to address challenges arising from the gas impermeable nature of PMMA. These features included a bubble trap and air micro-tanks to supply O2 for enzymatic reactions. We rigorously characterized the performance of the microfluidic device and demonstrated that the quality of plasma extracted in the device is comparable to a standard plasma isolation method involving centrifugation. We also showed close agreement between glucose levels measured in the device and by standard assay. As a final demonstration of utility, we loaded 5 {micro}L of blood, isolated plasma and detected three analytes simultaneously - glucose, lactate and H2O2. In addition to minimizing the volume of blood and eliminating standard laboratory equipment (e.g., centrifuge), our device enabled a rapid response (<10 min). The use of thermoplastic materials may pave the way for inexpensive, mass-produced automated microfluidic devices for rapid detection of blood biomarkers at the point of care.

bioengineering↗

bioRxiv2025

Intestinal Stem Cells Retain an Epigenetic Memory of Prior Inflammation

Intestinal epithelial damage and impaired repair are hallmarks of ulcerative colitis (UC), even after inflammation resolves. Intestinal stem cells (ISCs) can retain stable epigenetic changes after inflammation, highlighting the potential for long-lived epithelial memory in the gut. Inflammatory injury in barrier tissues induces epigenetic memory in epithelial stem cells, and the tendency of UC to relapse at previously inflamed sites led us to hypothesize that ISCs from IBD patients acquire lasting memory of prior inflammation. To test this, we derived colonic organoids from inflamed and uninflamed regions of the same UC patients and propagated in long-term culture. Chromatin profiling revealed 2,252 accessible regions unique to prior-inflamed (PI) organoids, associated with stress response, repair, and inflammatory genes. Although these regions remained accessible, [~]95% of associated genes were not upregulated in PI organoids, indicating a primed state. Upon inflammatory or injury re-challenge, PI organoids exhibited heightened transcriptional responses and accelerated wound closure, despite reduced clonogenicity and impaired barrier function, indicating a retained inflammatory memory program. Our findings demonstrate that human ISCs retain a chromatin-based memory of inflammation that persists in the absence of immune cues and shapes future responses to injury. While this may support epithelial adaptation to secondary insults, it may predispose tissue to relapse in patients with UC.

molecular biology↗

bioRxiv2023

Nanoprojectile Secondary Ion Mass Spectrometry Enables Multiplexed Analysis of Individual Hepatic Extracellular Vesicles

Extracellular vesicles (EVs) are nanoscale lipid bilayer particles secreted by cells. EVs may carry markers of the tissue of origin and its disease state which makes them incredibly promising for disease diagnosis and surveillance. While the armamentarium of EV analysis technologies is rapidly expanding, there remains a strong need for multiparametric analysis with single EV resolution. Nanoprojectile (NP) secondary ion mass spectrometry (NP-SIMS) relies on bombarding a substrate of interest with individual gold NPs resolved in time and space. Each projectile creates an impact crater of 10-20 nm in diameter while molecules emitted from each impact are mass analyzed and recorded as individual mass spectra. We demonstrate the utility of NP-SIMS for analysis of single EVs derived from normal liver cells (hepatocytes) and liver cancer cells. EVs were captured on antibody (Ab)-functionalized gold substrate then labeled with Abs carrying lanthanide (Ln) MS tags (Ab@Ln). These tags targeted four markers selected for identifying all EVs, and specific to hepatocytes or liver cancer. NP-SIMS was used to detect Ab@Ln-tags co-localized on the same EV and to construct scatter plots of surface marker expression for thousands of EVs with the capability of categorizing individual EVs. Additionally, NP-SIMS revealed information about the chemical nano-environment where targeted moieties co-localized. Our approach allowed analysis of population heterogeneity with single EV resolution and distinguishing between hepatocyte and liver cancer EVs based on surface marker expression. NP-SIMS holds considerable promise for multiplexed analysis of single EVs and may become a valuable tool for identifying and validating EV biomarkers of cancer and other diseases.

bioengineering↗

bioRxiv2022

A MICROFLUIDIC DEVICE FOR LONG-TERM MAINTENANCE OF ORGANOTYPIC LIVER CULTURES

Liver cultures may be used for modeling disease progression, testing therapies and predicting drug induced liver injury. The complexity of the liver cultures has evolved over the years from monocultures of hepatocytes to co-cultures with non-parenchymal cells and finally to precision cut liver slices. The latter culture format retains biomolecular and cellular complexity of the native liver and therefore holds considerable promise for in vitro testing. However, liver slices remain functional for ~72 h in vitro and hold only limited utility for some of the disease modeling and therapy testing applications that require longer culture times. This paper describes a microfluidic device for longer-term maintenance of functional organotypic liver cultures. Our microfluidic culture system was designed to enable direct injection of liver tissue into a culture chamber through a valve-enabled side port. Liver tissue was embedded in collagen and remained functional for up to 31 days as highlighted by continued production of albumin. These organotypic cultures also produced bile and urea and expressed several enzymes involved in metabolism of xenobiotics. In contrast, matched liver tissue embedded in collagen and cultured in the same media in a 96-well plate lost its phenotype and function on the timescale of 3 to 5 days. The microfluidic organotypic liver cultures described here represent a significant advance in liver cultivation and may be used in the future for modeling liver diseases or for individualized selection of liver-directed therapies.

bioengineering↗

bioRxiv2021

Bioactive Hydrogel Microcapsules for Guiding Stem Cell Fate Decisions by Release and Reloading of Growth Factors

Human pluripotent stem cells (hPSC) hold considerable promise as a source of adult cells for treatment of diseases ranging from diabetes to liver failure. Some of the challenges that limit the clinical/translational impact of hPSCs are high cost and difficulty in scaling-up of existing differentiation protocols. In this paper, we sought to address these challenges through the development of bioactive microcapsules. A co-axial flow focusing microfluidic device was used to encapsulate hPSCs in microcapsules comprised of an aqueous core and a hydrogel shell. Importantly, the shell contained heparin moieties for growth factor (GF) binding and release. The aqueous core enabled rapid aggregation of hPSCs into 3D spheroids while the bioactive hydrogel shell was used to load inductive cues driving pluripotency maintenance and endodermal differentiation. Specifically, we demonstrated that one-time 1h long loading of pluripotency signals, fibroblast growth factor (FGF)-2 and transforming growth factor (TGF)-{beta}1, into bioactive microcapsules was sufficient to induce and maintain pluripotency of hPSCs over the course of 5 days at levels similar to or better than a standard protocol with soluble GFs. Furthermore, stem cell-carrying microcapsules that previously contained pluripotency signals could be reloaded with an endodermal cue, Nodal, resulting in higher levels of endodermal markers compared to stem cells differentiated in a standard protocol. Overall, bioactive heparin-containing core-shell microcapsules decreased GF usage five-fold while improving stem cell phenotype and are well suited for 3D cultivation of hPSCs.

bioengineering↗