Research

In our laboratory, we use optical trapping and other light based techniques to manipulate microorganisms, investigate light matter interactions, and develop new biophotonic technologies. Light can be used to image microscopic objects, cells, and microorganisms, characterize the properties of biological and synthetic materials, and study how biological systems respond to optical exposure. Focused laser beams can also trap, move, and organize microscopic objects with high precision. We shape and control light in space and time, develop novel optical micromanipulation and spectroscopy techniques, investigate light transmission through scattering biological media, study the optical properties and biological effects of microplastics and nanoplastics, and engineer new light-based systems for biomedical and environmental applications.

Optical Trapping

Optical Tweezers use radiation pressure from a focused laser beam to attract particle to to the the center of the beam (the highest intensity).
Gradient Force - the intensity is greatest at the center of the beam, which pulls the particle towards the center of the beam.

F_grad ∝ ∇I
Scattering Force - it is created by light scattering of the surface of the particle, it pushes the particle along in the propagation direction.
F_scat ∝ I
For sharply focused beams an equilibrium position can exist slightly past the beam focus at which a particle is trapped.

Link to Optical Tweezers Simulation program from University of Colorado Boulder: Simulation program

Optically controlled biofim formation

We investigate how light can be used to control and manipulate the growth and development of biofilms. Biofilms form when bacteria encounter unfavorable or hostile environmental conditions and produce a protective, highly organized community structure. To explore this concept, we study B. Subtilis behaviour in minimal salts glycerol glutamate (MSgg) medium. Low nutrition environment induces the bacteria to secrete an extracellular polymeric substance (EPS), glue-like substance, and form a biofilm.
In 2024 paper, we investigate the effect of optical trapping with different lasers on the bacterial aggregation and biofilm development. Specifically, we determine the most advantageous stage of bacterial biofilm formation for optical manipulation and investigate the impact of optical trapping at different wavelengths on the aggregation of bacterial cells and the formation of biofilm. The investigation of optically regulated biofilm formation with optical tweezers presents innovative methodologies for the stimulation and suppression of biofilm growth through the application of lasers.
Our laboratory is now expanding this research to investigate how different wavelengths of light affect other bacterial and biofilm responses, including growth, structural development, and responses to environmental stress. We are also developing optical spectroscopy approaches to characterize biochemical changes in bacterial cells and biofilms.

Optical studies of microplastics and nanoplastics and their effect on cells

We investigate the optical properties of microplastics and nanoplastics and their interactions with biological systems. Plastic waste gradually degrades into micro- and nanoscale particles that contaminate water, soil, and air and may enter food chains and interact with cells and microorganisms. Understanding the physical and optical properties of these particles is essential for developing methods to manipulate them and study their biological effects at the microscopic scale.
In our 2025 study, we investigated the optical trapping stability of irregularly shaped, mechanically weathered microplastics composed of polypropylene (PP), polyethylene terephthalate (PET), and high-density polyethylene (HDPE). Using optical tweezers, we examined how polymer composition, particle size, shape, and color-dependent optical absorption influence trapping stability. We found that irregularly shaped PP particles were the most stable in a single-beam optical trap, whereas PET particles were the least stable. Trapping stability for PP and HDPE was relatively independent of particle size, while PET particles larger than 10 µm were substantially less likely to remain stably trapped. More strongly absorbing, nontransparent particles also exhibited reduced trapping stability.
These results provide a foundation for future studies of optically controlled interactions between microplastics and biological systems at the single-cell level. Our laboratory is now expanding this research to examine how different types of nanoplastics affect the physical and functional properties of cells.

Biological Waveguides

In biological soft-matter environments, such as blood or biological fluids, light typically experiences strong scattering losses, preventing long distance propagation of light. Such losses limit the development of imaging technologies and transmissive light applications. In our lab we demonstrated nonlinear self-trapping and the formation of biological waveguides of several centimeters long without significant photodamage in suspensions of bacteria and red blood cells (RBCs). Since living cells usually have a slightly higher index of refraction than the surrounding media, suspended microorganisms in biological waveguides get attracted toward the center of the continuous-wavelaser beam due to the optical gradient force and pushed forward by the forward scattering force. As a result, hundreds of living cells get trapped along the propagating focused laser beam. The laser beam traps particles near the focus and propels them forward resulting in selffocusing of the beam due to a cumulative particle lensing effect along the beam path, which allows the formation of a biological optical fiber or a biological optical conduit.
In our 2022 study, we demonstrated that these self-arranged biological waveguides can preserve important photonic properties over several centimeters. Polarization and orbital angular momentum were maintained, and additional probe beams could be coupled into and guided through the waveguides with minimal degradation of the encoded optical information. These results suggest potential applications in photonic biosensing, optical communication through biological media, and noninvasive biomedical imaging.
More recently, our 2025 study examined the linear and nonlinear optical properties of plasmid, lambda, and strawberry DNA suspensions. The results showed that DNA suspensions have promising optical characteristics and remain structurally stable under prolonged 532 nm laser exposure, supporting their potential use in photonic and optoelectronic applications.

Copyright © 2019 - All Rights Reserved - Bezryadina Lab @CSUN

Template by OS Templates