Lindley, M. | Search bioRxiv

bioRxiv2025

Accelerated plastic aging in suspension (APAS): A simple, reproducible approach for the generation of model micro- and nanoplastics through simulated environmental forces

The environmental fragmentation of plastic waste leads to the formation of micro- and nanoplastics (MNPs), which pose serious ecological and human health concerns. Despite increasing interest in their biological effects, many studies rely on artificial, uniform particles that fail to mimic the diverse physical and chemical characteristics of real-world MNPs. To address this limitation, we developed the Accelerated Plastic Aging in Suspension (APAS) system--a scalable, reproducible method that mimics natural aging processes by combining ultraviolet (UV) radiation, thermal stress, and mechanical shear to generate environmentally relevant MNPs from commonly used polymers. We used APAS to fragment polyethylene terephthalate (PET), polyamide 6 (Nylon), and polyacrylonitrile (PAN), and observed time-dependent degradation, including the spontaneous formation of nanoplastics (<100 nm). Flow cytometry revealed substantial increases in particle number and reductions in average particle size over 12 weeks. Imaging flow cytometry confirmed consistent generation of heterogeneous, irregular particles across replicate batches. High-resolution imaging via AFM, TEM, and SEM confirmed the presence of nanoplastics with textured and irregular morphologies. Chemical characterization showed APAS aging altered particle surface charge and induced polymer-specific changes in autofluorescence and Raman spectral profiles, consistent with oxidative surface modifications. Laser Direct Infrared (LDIR) imaging further confirmed structural and chemical changes in polymer spectra post-aging. Functionally, under physiologically relevant shear flow conditions, endothelial cells internalized APAS-generated PET MNPs at significantly higher levels than polystyrene (PS) beads of similar size. Uptake was enhanced particularly under oscillatory flow, highlighting the influence of particle physicochemical properties on cellular interactions. Together, these findings demonstrate the ability of the APAS system to produce complex and realistic MNPs for use in environmental and toxicological studies. The system enables generation of nanoplastics and supports more accurate modelling of biological exposure scenarios compared to conventional synthetic particles.

pharmacology and toxicology↗

bioRxiv2024

Raman flow cytometry using time delay integration

Raman flow cytometry offers chemically sensitive, label-free measurement of cells and particles; however, the technique suffers from low cell throughput due to the weak Raman signal. Here, we demonstrate the use of time-delay integration to achieve Raman flow cytometry combined with dual-sided line illumination. The use of line illumination from both sides of the cell flow capillary kept the cell stream in the detection area by balancing optical force from the illumination lines. The time-delay integration allowed accumulation of Raman signals from flowing cells without sacrificing the spectrum readout rate. With the developed system, we achieved Raman flow cytometry at throughputs of 32 and 75 events per second for cell and particle detection, respectively. We applied the technique for analyzing lipid uptake in HepG2 cells and degranulation in bone marrow-derived murine mast cells.

biophysics↗

bioRxiv2021

High-throughput Raman-activated cell sorting in the fingerprint region

Cell sorting is the workhorse of biological research and medicine. Cell sorters are commonly used to sort heterogeneous cell populations based on their intrinsic features. Raman-activated cell sorting (RACS) has recently received considerable interest by virtue of its ability to discriminate cells by their intracellular chemical content, in a label-free manner. However, broad deployment of RACS beyond lab-based demonstrations is hindered by a fundamental trade-off between throughput and measurement bandwidth (i.e., cellular information content). Here we overcome this trade-off and demonstrate broadband RACS in the fingerprint region (300 - 1,600 cm-1) with a record high throughput of ~50 cells per second. This represents a 100x throughput increase compared to previous demonstrations of broadband fingerprint-region RACS. To show the utility of our RACS, we demonstrate real-time label-free sorting of microalgal cells based on their accumulation of carotenoids and polysaccharide granules. These results hold promise for medical, biofuel, and bioplastic applications.

bioengineering↗