The Effect of Substrate Temperature on the Evaporative Behaviour and Desiccation Patterns of Foetal Bovine Serum Drops

Abstract

The drying of bio-fluid drops results in the formation of complex patterns, which are morphologically and topographically affected by environmental conditions including temperature. We examine the effect of substrate temperatures between 20 °C and 40 °C, on the evaporative dynamics and dried deposits of foetal bovine serum (FBS) drops. The deposits consist of four zones: a peripheral protein ring, a zone of protein structures, a protein gel, and a central crystalline zone. We investigate the link between the evaporative behaviour, final deposit volume, and cracking. Drops dried at higher substrate temperatures in the range of 20 °C to 35 °C produce deposits of lower final volume. We attribute this to a lower water content and a more brittle gel in the deposits formed at higher temperatures. However, the average deposit volume is higher for drops dried at 40 °C compared to drops dried at 35 °C, indicating protein denaturation. Focusing on the protein ring, we show that the ring volume decreases with increasing temperature from 20 °C to 35 °C, whereas the number of cracks increases due to faster water evaporation. Interestingly, for deposits of drops dried at 40 °C, the ring volume increases, but the number of cracks also increases, suggesting an interplay between water evaporation and increasing strain in the deposits due to protein denaturation.

Hierarchical Exploration of Drying Patterns Formed in Drops Containing Lysozyme, PBS, and Liquid Crystals

“…Furthermore, a few recent studies examined the formation of these protein-saline drying drops at different elevated substrate temperatures. The findings of these experiments confirmed that the final morphological patterns are mainly dependent on the environmental conditions (higher vs. lower drying rate) [24][25][26].…”

Drying Patterns of Cerebrospinal Fluid as Indicator for Alzheimer’s Disease by a Machine Learning Framework

“…Figure 1 (a -b) shows an example of the patterns formed by a dried drop of CSF from a healthy patient. In the formation of these patterns, various hydrodynamic and physicochemical processes occur that depend on various conditions, such as temperature and humidity, resulting in complex fractal-like patterns [16].…”

Patterns in Dried Droplets to Detect Unfolded BSA

“…The occurrence of patterns in deposits is a frequent phenomenon that emerges in drying droplets with nonvolatile species [ 19 , 20 , 21 , 22 ]. The literature reveals that the coffee ring can appear in both simple and complex droplet systems [ 23 , 24 , 25 , 26 ]. The “coffee-ring effect” is a ring-like shape pattern observed in the evaporation of droplets containing suspensions [ 27 ], large colloids, nanoparticles [ 28 ], or individual molecules [ 29 ].…”

“…By contrast, at low RH, the ions attach at random positions, resulting in amorphous crystal structures. The substrate temperature can strongly affect the modes of drying and the final pattern of colloidal and protein drops [ 24 , 52 , 53 , 54 ]. Indeed, the interesting pattern called “eye-like pattern”, a large aggregate enclosed in a uniform coating, results from a conformational change from native to irreversible folding of proteins induced by a hot substrate [ 54 ].…”

“…Although in the scientific literature, several works report the pattern formation of dried droplets of proteins [ 24 , 40 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 52 , 53 , 54 , 55 ], the effectiveness of this method to reveal the coexistence of macromolecules of the same species, with different conformational states, is still unknown. Advances in strategies to detect conformational changes in proteins through the analysis of deposits could lead to the development of rapid methodologies capable of diagnosing pathologies.…”