Engineering Cellular Photocomposite Materials Using Convective Assembly

Abstract

Fabricating industrial-scale photoreactive composite materials containing living cells, requires a deposition strategy that unifies colloid science and cell biology. Convective assembly can rapidly deposit suspended particles, including whole cells and waterborne latex polymer particles into thin (<10 µm thick), organized films with engineered adhesion, composition, thickness, and particle packing. These highly ordered composites can stabilize the diverse functions of photosynthetic cells for use as biophotoabsorbers, as artificial leaves for hydrogen or oxygen evolution, carbon dioxide assimilation, and add self-cleaning capabilities for releasing or digesting surface contaminants. This paper reviews the non-biological convective assembly literature, with an emphasis on how the method can be modified to deposit living cells starting from a batch process to its current state as a continuous process capable of fabricating larger multi-layer biocomposite coatings from diverse particle suspensions. Further development of this method will help solve the challenges of engineering multi-layered cellular photocomposite materials with high reactivity, stability, and robustness by clarifying how process, substrate, and particle parameters affect coating microstructure. We also describe how these methods can be used to selectively immobilize photosynthetic cells to create biomimetic leaves and compare these biocomposite coatings to other cellular encapsulation systems.

Biocoatings: A new challenge for environmental biotechnology

“…This is analogous to the maximum or critical pigment volume concentration (PVC) in latex paints [88]. However, the presence of high concentrations of cells can decrease porosity and block polymer particle coalescence depending on cell size and the interaction between the cell surface and the surface of the polymer particles [12]. Biocoatings with E. coli densities as high as 50% by volume, 2 × 10 11 cells cm −3 of coating volume, have been reported [89].…”

“…Some whole cell biocatalysts can be stabilized with minimum preparation, e.g., adsorption onto an insoluble support, hydrogel entrapment with cross linking, as natural biofilms, simple drying, or lyophilization. All these methods reduce expensive enzyme purification [6,7,12]. Immobilized cells may be used in a growing or non-growing state [13] or even as metabolically inactive cells [14].…”

“…Nanoporosity is generated by the addition of glycerol and carbohydrates to arrest polymer particle coalescence during film formation of low T g emulsions. These additives also protect the entrapped cells from osmotic stress during coating formation prior to deposition [12]. However, when rehydrated, the entrapped porogens are leached and porosity can slowly be lost as a function of time and temperature as a result of wet coalescence [67].…”

Artificial leaf device for hydrogen generation from immobilised C. reinhardtii microalgae

“…These sheet-like hydrogen producing devices can be deployed in many areas, which are presently unsuitable for larger and more expensive photobioreactors. 35,36 There are many different kinds of microorganisms which can utilise light for hydrogen production and which can be tested with this system for more efficient light utilisation and thereby hydrogen production. Recently, C. reinhardtii cells were genetically modied and the hydrogen production was increased ve folds.…”

Agriculture-independent, sustainable, fail-safe and efficient food production by autotrophic single-cell protein

“…Coated Paper Array Contactor are composed of paper matrices on which convective assembly of living cells and adhesive latex particles forms colloid-latex biocomposite adhesive coatings [96,97,98]. While the paper provides mechanical stability, hydration and diffusion of products, 1 st stage bacteria are entrapped at high density in the microporous latex film which prevents biomass outgrowth while still permitting a reasonable exchange of substrate gases and acetate.…”