Hydrogel-based commercial products for biomedical applications: A review.

Converting Escherichia coli to a Synthetic Methylotroph Growing Solely on Methanol

The “trash to treasure” process has been extensively demonstrated for various energy and environmental issues in the past few decades. Abundant biomass is well accepted as a carbon-rich, sustainable, and renewable precursor, offering us a plethora of possibilities for advanced materials for energy conversion and storage as well as environmental treatments; spatial modification of biomass facilitates the formation of a unique three-dimensional (3D) structure with micro- to macropores, yielding higher surface area and enhanced physicochemical properties. This novel concept provides sufficient reaction sites, excellent adsorption capability, more activated sites for catalyst doping, and fascinating electrochemical performance. Basically, the 3D cadre of biomass-derived carbon strengthens the economic competitiveness of these materials and broadens their applications in fields such as in supercapacitors, chemical batteries, bioenergy harvest, adsorbents for organic pollutants and greenhouse gases, and efficient (photo)catalysts. The scope of this review mainly focuses on the most popular synthesis methodology of three-dimensional carbon materials derived from biomass and their critical applications in the fields of energy and environment.

Upgrading earth-abundant biomass into three-dimensional carbon materials for energy and environmental applications

Three-dimensional (3D) porous networks of planar 2D graphene have attractive features with respect to sensing. These include a large electroactive surface area, good inner and outer surface contact with the analyte, ease of loading with (bio)catalysts, and good electrochemical sensitivity. 3D free-standing graphene can even be used directly as an electrode. This review (with 140 refs.) covers the progress made in the past years. Following an introduction into the field (including definitions), a large section is presented that covers methods for the synthesis of 3D graphene (3DG) (including chemical vapor deposition, hydrothermal methods, lithography, support assisted synthesis and chemical deposition, and direct electrochemical methods). The next section covers the key features of 3DG and its composites for use in electrochemical sensors. This section is subdivided into sections on the uses of 3D porous graphene, 3DG composites with metals and metal oxides, composites consisting of 3DG and organic polymers, and electrodes modified with 3DG, 3DGs decorated with carbon nanotubes, and others. The review concludes with a discussion of future perspectives and current challenges. Graphical Abstract A schematic of the key characteristics of three-dimensional (3D) graphene.

Electrodes modified with 3D graphene composites: a review on methods for preparation, properties and sensing applications

The popularity of hydrogels as biomaterials lies in their tunable physical properties, ability to encapsulate small molecules and macromolecular drugs, water holding capacity, flexibility, and controllable degradability. Functionalization strategies to overcome the deficiencies of conventional hydrogels and expand the role of advanced hydrogels such as DNA hydrogels are extensively discussed in this review. Different types of cross-linking techniques, materials utilized, procedures, advantages, and disadvantages covering hydrogels are tabulated. The application of hydrogels, particularly in buccal, oral, vaginal, and transdermal drug delivery systems, are described. The review also focuses on composite hydrogels with enhanced properties that are being developed to meet the diverse demand of wound dressing materials. The unique advantages of hydrogel nanoparticles in targeted and intracellular delivery of various therapeutic agents are explained. Furthermore, different types of hydrogel-based materials utilized for tissue engineering applications and fabrication of contact lens are discussed. The article also provides an overview of selected examples of commercial products launched particularly in the area of oral and ocular drug delivery systems and wound dressing materials. Hydrogels can be prepared with a wide variety of properties, achieving biostable, bioresorbable, and biodegradable polymer matrices, whose mechanical properties and degree of swelling are tailored with a specific application. These unique features give them a promising future in the fields of drug delivery systems and applied biomedicine.

Emerging Role of Hydrogels in Drug Delivery Systems, Tissue Engineering and Wound Management.

A viable approach for methanol production under ambient physiological conditions is to use greenhouse gases, methane (CH4) and carbon dioxide (CO2), as feed for immobilized methanotrophs. In the present study, unique macroporous carbon particles with pore sizes in the range of ∼1-6 μm were synthesized and used as support for the immobilization of Methylocella tundrae. Immobilization was accomplished covalently on hierarchical macroporous carbon particles. Maximal cell loading of covalently immobilized M. tundrae was 205 mgDCM g-1 of particles. Among these particles, the cells immobilized on 3.6 μm pore size particles showed the highest reusability with the least leaching and were chosen for further study. After immobilization, M. tundrae showed up to 2.4-fold higher methanol production stability at various pH and temperature values because of higher stability and metabolic activity than free cells. After eight cycles of reuse, the immobilized cells retained 18.1-fold higher relative production stability compared to free cells. Free and immobilized cells exhibited cumulative methanol production of 5.2 and 9.5 μmol mgDCM-1 under repeated batch conditions using simulated biogas [CH4 and CO2, 4:1 (v/v)] as feed, respectively. The appropriate pore size of macroporous particles favors the efficient M. tundrae immobilization to retain better biocatalytic properties. This is the first report concerning the covalent immobilization of methanotrophs on the newly synthesized macroporous carbon particles and its subsequent application in repeated methanol production using simulated biogas as a feed.

Hierarchical Macroporous Particles for Efficient Whole-Cell Immobilization: Application in Bioconversion of Greenhouse Gases to Methanol.

Acetogenic bacteria use cellular redox energy to convert CO2 to acetate using the Wood-Ljungdahl (WL) pathway. Such redox energy can be derived from electrons generated from H2 as well as from inorganic materials, such as photoresponsive semiconductors. We have developed a nanoparticle-microbe hybrid system in which chemically synthesized cadmium sulfide nanoparticles (CdS-NPs) are displayed on the cell surface of the industrial acetogen Clostridium autoethanogenum The hybrid system converts CO2 into acetate without the need for additional energy sources, such as H2, and uses only light-induced electrons from CdS-NPs. To elucidate the underlying mechanism by which C. autoethanogenum uses electrons generated from external energy sources to reduce CO2, we performed transcriptional analysis. Our results indicate that genes encoding the metal ion or flavin-binding proteins were highly up-regulated under CdS-driven autotrophic conditions along with the activation of genes associated with the WL pathway and energy conservation system. Furthermore, the addition of these cofactors increased the CO2 fixation rate under light-exposure conditions. Our results demonstrate the potential to improve the efficiency of artificial photosynthesis systems based on acetogenic bacteria integrated with photoresponsive nanoparticles.

https://www.pnas.org/content/pnas/118/9/e2020552118.full.pdf

Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth.

Visibly Clear Radiative Cooling Metamaterials for Enhanced Thermal Management in Solar Cells and Windows

Fabrication of three-dimensional porous carbon scaffolds with tunable pore sizes for effective cell confinement

An important pathway for cost-effective light energy conversion devices, such as solar cells and light emitting diodes, is to integrate III–V (e.g., GaN) materials on Si substrates. Such integration first necessitates growth of high crystalline III–V materials on Si, which has been the focus of many studies. However, the integration also requires that the final III–V/Si structure has a high light energy conversion efficiency. To accomplish these twin goals, we use single-crystalline microsized Si pillars as a seed layer to first grow faceted Si structures, which are then used for the heteroepitaxial growth of faceted GaN films. These faceted GaN films on Si have high crystallinity, and their threading dislocation density is similar to that of GaN grown on sapphire. In addition, the final faceted GaN/Si structure has great light absorption and extraction characteristics, leading to improved performance for GaN-on-Si light energy conversion devices.

Min Soo Jeon

Papers

Hierarchical Macroporous Particles for Efficient Whole-Cell Immobilization: Application in Bioconversion of Greenhouse Gases to Methanol.

Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth.

Visibly Clear Radiative Cooling Metamaterials for Enhanced Thermal Management in Solar Cells and Windows

Fabrication of three-dimensional porous carbon scaffolds with tunable pore sizes for effective cell confinement

Three-Dimensional Hetero-Integration of Faceted GaN on Si Pillars for Efficient Light Energy Conversion Devices