Lab on a Chip Blog

From space shuttles to military equipment, or even the kitchenware that we use on daily basis, lasers have found use in more places than we often realise. Interestingly, the solid-state lasers were believed to be a solution to an unknown problem after their invention in 1950s. In that time nobody—including their developer Charles Townes—noticed that the lasers were one of the game changer inventions in the world’s history. After tens of years, in 1964, the laser technology was awarded with a Nobel prize when its potential for diverse applications were realized.

So far we have only discussed solid-state lasers, but there is definitely capacity in the laser world to improve the performance and versatility with the help of little twists, such as optofluidic lasers. “Optofluidics” is a synergic combination of optical systems and microfluidics. In other words, optical systems are built or synthesized from liquids, aiming to serve as good as their solid-state equivalents. For example, two immiscible liquids form a smooth surface in their interface, leading to a laser cavity or an optical resonator with a very high Q-factor that allows for operating at low energy levels. This emerging field gains importance when considering most of the biochemical reactions that occur in aqueous environments. Optofluidic laser systems are flexible to change their optical properties by just replacing the liquid media; and with this twist, lasers have new application areas including diagnosis of genetic disorders at the cellular level and in vivo biosensing.

What is more exciting about the optofluidic lasers is that they can be biodegradable and easily tunable in microenvironments. Researchers in University of Michigan recently showed that one of the most abundant pigments on earth, chlorophylls, can maintain both biodegradability and tunability in optical systems owing to their fluorescence capabilities. Chlorophylls have a high Q-factor, dual-absorption bands in the visible spectrum, and a large shift between absorption and emission bands, suggesting that chlorophylls can be used as donors in fluorescence resonance energy transfer (FRET) laser (Figure 1). In this study, chlorophyll a was isolated from spinach leaf and used as the gain medium and the donor to develop a novel optofluidic laser. Two lasing bands of chlorophyll a was investigated by both theoretical and experimental means. Concentration-dependent studies enabled more insight for the mechanism determining when, where, and why the laser emission band appears. This new technique seems to gain increasing attention for applications in in vivo and in vitro biosensing, solar lighting and energy harvesting.

Before the 1700’s, when dissection techniques were not yet available, the cause of mood changes were thought to be the replacement of liquids and vapors in the body. The biology of the brain has been better understood since the discovery of research and test tools. However, occupying only about 1/50 of the body mass, the brain is perhaps the most complicated organ to study. National Institute of Neurological Disorders and Stroke’s list of over 400 neurological disorders can be seen as a sound proof of this exciting- and frustrating- fact.

Figure 1. The effects of biomechanical forces on the brain

Biomechanical forces on neurons play a fundamental role in neuronal physiology, which, in turn, affect brain development and disorders. During the growth of neurons, the tension created by the biomechanical forces are suggested to influence the cells’ motor activities, gene expression, neurotransmitter release, together with neurite growth and network connections (Figure 1). Research on the biomechanical forces can definitely help us to understand how the brain works, but many questions related to these forces remain unanswered. Quantitative measurements of the cell activity seem to be the only possible path to find satisfying answers to those questions.

A comprehensive list of experimental techniques involving both conventional and alternative micro&nanotechnology approaches have been recently brought to the attention of scientific community by Di Carlo and his coauthors. In their recent critical review, both advantages and disadvantages of conventional tools—namely motor-driven pressure, patch membrane pressure, osmotic pressure, fluid shear stresses, and deformation of flexible elastomers—, microtechnology tools—including atomic force microscopy, micropatterning, and some other potential techniques—, and nanotechnology tools—such as ferromagnetic and piezoelectric nanoparticles— are discussed.

The literature reports provided in the paper suggest that micro and nanotechnology tools offer better spatiotemporal resolution and throughput when compared to conventional techniques. The cellular functions and the possible technologies for the characterization of those functions are further described (Figure 2). For instance, behind-the-scene biological mechanisms for recovery in traumatic brain injuries can be determined by applying the biomechanical forces at the right place and right time to ultimately mitigate the injuries.

Figure 2. The influence of biomechanical forces on the neuron functions and available technologies for their investigation.

This article, published on 26 April 2016, is included in the Lab on a Chip Recent HOT Articles themed collection.

To download the full article for free* click the link below:

Micro- and nano-technologies to probe the mechano-biology of the brain
Andy Tay, Felix E. Schweizer, and Dino Di Carlo
Lab Chip, 2016,16, 1962-1977
DOI: 10.1039/C6LC00349D, Critical Review

—————-

About the webwriter

Burcu Gumuscu is a PhD researcher in BIOS Lab on a Chip Group at University of Twente in The Netherlands. Her research interests include development of microfluidic devices for second generation sequencing, organ-on-chip development, and desalination of water on the micron-scale.

—————-

*Access is free until 15/08/2016 through a registered RSC account.