Molecular insight into COF monolayers for urea sorption in artificial kidneys

Urea removal from an aqueous solution is considered a challenge in the biological process. The state of complete kidney destruction is known as an end-stage renal disease (ESRD). Kidney transplant and hemodialysis are the most common methods for confronting ESRD. More recently, wearable artificial kidney (WAK) devices have shown a significant improvement in urea removal performance. However, low efficiency in physical adsorbents is a barrier in developing them. For the first time, the urea adsorption capacity of five types of last-generation covalent organic framework (COF) nanosheets (NSs) was investigated in this study by applying molecular dynamics (MD) simulation tools. To this end, different analyses have been performed to evaluate the performance of each nanoparticle. The MD all-atom (AA) results demonstrated that all introduced COF NSs had urea removal capacity. Among the five NSs, TPA-COF was shown to have the best outcomes. Moreover, coarse-grained (CG) and density functional theory (DFT) simulations were conducted, and the results show that the TPA-COF nanoparticle modified with –OH functional group has even better properties for urea adsorption. The present molecular study sheds new light on COF NSs as an adsorbent for urea removal.

Molecular insight into optimizing the N- and P-doped fullerenes for urea removal in wearable artificial kidneys

Urea is the result of the breakdown of proteins in the liver, the excess of which circulates in the blood and is adsorbed by the kidneys. However, in the case of kidney diseases, some products, specifically urea, cannot be removed from the blood by the kidneys and causes serious health problems. The end-stage renal disease (ESRD) patients are not able to purify their blood, which endangers their life. ESRD patients require dialysis, a costly and difficult method of urea removal from the blood. Wearable artificial kidneys (WAKs) are consequently designed to remove the waste from blood. Regarding the great amount of daily urea production in the body, WAKs should contain strong and selective urea adsorbents. Fullerenes—which possess fascinating chemical properties—have been considered herein to develop novel urea removal adsorbents. Molecular dynamics (MD) has enabled researchers to study the interaction of different materials and can pave the way toward facilitating the development of wearable devices. In this study, urea adsorption by N-doped fullerenes and P-doped fullerenes were assessed through MD simulations. The urea adsorption was simulated by five samples of fullerenes, with phosphorous and different nitrogen dopant contents. For comparing the urea adsorption capacity in the performed simulations, detailed characteristics—including the energy analysis, radius of gyration, radial distribution function (RDF), root-mean-square fluctuation (RMSD), and H-bond analyses were investigated. It had been determined that the fullerene containing 8% nitrogen—with the highest reduction in the radius of gyration, the maximum RDF, a high adsorption energy, and a high number of hydrogen bonds—adsorbs urea more efficiently.

Chitosan: A Natural Biopolymer with a Wide and Varied Range of Applications

Although chitin is of the most available biopolymers on Earth its uses and applications are limited due to its low solubility. The deacetylation of chitin leads to chitosan. This biopolymer, composed of randomly distributed β-(1-4)-linked D-units, has better physicochemical properties due to the facts that it is possible to dissolve this biopolymer under acidic conditions, it can adopt several conformations or structures and it can be functionalized with a wide range of functional groups to modulate its superficial composition to a specific application. Chitosan is considered a highly biocompatible biopolymer due to its biodegradability, bioadhesivity and bioactivity in such a way this biopolymer displays a wide range of applications. Thus, chitosan is a promising biopolymer for numerous applications in the biomedical field (skin, bone, tissue engineering, artificial kidneys, nerves, livers, wound healing). This biopolymer is also employed to trap both organic compounds and dyes or for the selective separation of binary mixtures. In addition, chitosan can also be used as catalyst or can be used as starting molecule to obtain high added value products. Considering these premises, this review is focused on the structure and modification of chitosan as well as its uses and applications.

Dielectrophoresis Manipulation: Versatile Lateral and Vertical Mechanisms

Discussing the topic of the capability of dielectrophoresis (DEP) devices in terms of the selective detection and rapid manipulation of particles based on the DEP force (FDEP) via contactless methods is challenging in medical research, drug discovery and delivery. Nonetheless, the process of the selective detection and rapid manipulation of particles via contactless DEP based on dielectric particles and the surrounding medium can reduce the effects of major issues, including physical contact with the particles and medium contamination to overcome operational difficulties. In this review, DEP microelectromechanical system (MEMS) microelectrodes with a tapered profile for the selective detection and rapid manipulation of particles were studied and compared with those of conventional designs with a straight-cut profile. The main objective of this manuscript is to review the versatile mechanism of tapered DEP MEMS microelectrodes for the purpose of selective detection and rapid manipulation. Thus, this review provides a versatile filtration mechanism with the potential for a glomerular-based membrane in an artificial kidneys’ development solution for implementing engineered particles and cells by lateral attraction as well as vertical repulsion in the development of lab-on-a-chip applications. For tapered DEP MEMS microelectrodes, the scope of this study methodology involved the characterisation of DEP, modelling of the polarisation factor and the dynamic dielectric changes between the particles and medium. Comprehensive discussions are presented on the capability of tapered DEP microelectrodes to drive the selected particles and the simulation, fabrication and testing of the tapered profile. This study revealed an outstanding performance with the capability of producing two regions of high electric field intensity at the bottom and top edges of the side wall of tapered microelectrodes. Observations on particle separation mainly by the lateral attraction force of particles with positive DEP on the y-axis and vertical repulsion force of particles with negative DEP on the z-axis proved an efficient and uniform FDEP produced by tapered electrodes. In conclusion, this study confirmed the reliability and efficiency of the tapered DEP microelectrodes in the process of selective detection and rapid manipulation at a higher efficiency rate than straight-cut microelectrodes, which is significant in DEP technology applications.