Drying of Bio-colloidal Sessile Droplets: Advances, Applications, and Perspectives

TL;DR

This review summarizes recent advances in understanding the drying patterns of bio-colloidal droplets, highlighting their biomedical applications, diagnostic potential, and the influence of biological and environmental factors on pattern formation.

Contribution

It provides a comprehensive overview of experimental progress over the last decade, linking droplet composition to drying patterns and exploring applications in diagnostics and biomedical research.

Findings

Distinct morphological patterns depend on bio-colloid composition and environmental conditions.

Drying patterns can be used to detect clinical abnormalities.

Recent studies include bio-mimetic and salivary droplets relevant to COVID-19.

Abstract

Drying of biologically-relevant sessile droplets, including passive systems (like DNA and proteins), as well as active microbial systems comprising bacteria and algae, have garnered considerable attention over the last decades. Distinct morphological patterns emerge when bio-colloids undergo drying, with significant potential in a range of biomedical applications, spanning bio-sensing, medical diagnostics, drug delivery, and antimicrobial resistance. This review presents a comprehensive overview of bio-colloidal droplets drying on solid substrates, focusing on the experimental progress during the last ten years. We provide a summary of the relevant properties of bio-colloids and link their composition (constituent particles, solvent, and concentrations) to the patterns emerging due to drying. We examined the drying patterns generated by passive bio-colloids (DNA, globular, fibrous, and composite proteins, plasma, serum, blood, urine, tears, saliva). This article highlights how morphological patterns are influenced by the nature of the biological entities and the solvent, micro- and global environmental conditions. Correlations between emergent patterns and the initial droplet compositions enable the detection of potential clinical abnormalities when compared with the patterns of drying droplets of healthy control samples, offering a diagnostic blueprint. Recent experimental investigations of pattern formation in the bio-mimetic and salivary drying droplets, relevant to COVID-19 are also presented. Finally, we summarize the role of biologically active agents in drying process, including bacteria and algae during the drying process. The review concludes with a perspective on the next generation of research and applications based on drying droplets, enabling potential innovations and tools to study this exciting interface of physics, biology, data sciences, and machine learning.