Polymeric membrane materials for artificial organs

Polymeric membranes for biomedical applications

The rapid development of nanotechnology paved the way for further expansion of polymer chemistry and the fabrication of advanced polymeric membranes. Such modifications allowed enhancing or adding some unique properties, including mechanical strength, excellent biocompatibility, easily controlled degradability, and biological activity. This chapter discusses various applications of polymeric membranes in three significant areas of biomedicine, including tissue engineering, drug delivery systems, and diagnostics. It is intended to highlight here possible ways of improvement the properties of polymeric membranes, by modifying with other polymers, functional groups, compounds, drugs, bioactive components, and nanomaterials.

Effect of Unbleached Rice Straw Cellulose Nanofibers on the Properties of Polysulfone Membranes

In addition to their lower cost and more environmentally friendly nature, cellulose nanofibers isolated from unbleached pulps offer different surface properties and functionality than those isolated from bleached pulps. At the same time, nanofibers isolated from unbleached pulps keep interesting properties such as hydrophilicity and mechanical strength, close to those isolated from bleached pulps. In the current work, rice straw nanofibers (RSNF) isolated from unbleached neutral sulfite pulp (lignin content 14%) were used with polysulfone (PSF) polymer to make membrane via phase inversion. The effect of RSNF on microstructure, porosity, hydrophilicity, mechanical properties, water flux, and fouling of PSF membranes was studied. In addition, the prepared membranes were tested to remove lime nanoparticles, an example of medium-size nanoparticles. The results showed that using RSNF at loadings from 0.5 to 2 wt.% can significantly increase hydrophilicity, porosity, water flux, and antifouling properties of PSF. RSNF also brought about an increase in rejection of lime nanoparticles (up to 98% rejection) from their aqueous suspension, and at the same time, with increasing flux across the membranes. Tensile strength of the membranes improved by ~29% with addition of RSNF and the maximum improvement was obtained on using 0.5% of RSNF, while Young’s modulus improved by ~40% at the same RSNF loading. As compared to previous published results on using cellulose nanofibers isolated from bleached pulps, the obtained results in the current work showed potential application of nanofibers isolated from unbleached pulps for improving important properties of PSF membranes, such as hydrophilicity, water flux, rejection, and antifouling properties.

Ga-Based Alloys in Microelectronic Interconnects: A Review

Gallium (Ga) and some of its alloys have a range of properties that make them an attractive option for microelectronic interconnects, including low melting point, non-toxicity, and the ability to wet without fluxing most materials-including oxides-found in microelectronics. Some of these properties result from their ability to form stable high melting temperature solid solutions and intermetallic compounds with other metals, such as copper, nickel, and aluminium. Ga and Ga-based alloys have already received significant attention in the scientific literature given their potential for use in the liquid state. Their potential for enabling the miniaturisation and deformability of microelectronic devices has also been demonstrated. The low process temperatures, made possible by their low melting points, produce significant energy savings. However, there are still some issues that need to be addressed before their potential can be fully realised. Characterising Ga and Ga-based alloys, and their reactions with materials commonly used in the microelectronic industry, are thus a priority for the electronics industry. This review provides a summary of research related to the applications and characterisation of Ga-based alloys. If the potential of Ga-based alloys for low temperature bonding in microelectronics manufacturing is to be realised, more work needs to be done on their interactions with the wide range of substrate materials now being used in electronic circuitry.

Using Artificial Neural Networks and Model Predictive Control to Optimize Acoustically Assisted Doxorubicin Release from Polymeric Micelles

We have been developing a drug delivery system that uses Pluronic P105 micelles to sequester a chemotherapeutic drug - namely, Doxorubicin (Dox) - until it reaches the cancer site. Ultrasound is then applied to release the drug directly to the tumor and in the process minimize the adverse side effects of chemotherapy on non-tumor tissues. Here, we present an artificial neural network (ANN) model that attempts to model the dynamic release of Dox from P105 micelles under different ultrasonic power intensities at two frequencies. The developed ANN model is then utilized to optimize the ultrasound application to achieve a target drug release at the tumor site via an ANN-based model predictive control. The parameters of the controller are then tuned to achieve good reference signal tracking. We were successful in designing and testing a controller capable of adjusting the ultrasound frequency, intensity, and pulse length to sustain constant Dox release.

Ternary protein adsorption onto brushes: strong versus weak

Attractive interactions between proteins and polyethylene glycol (PEG) give rise to ternary adsorption within PEG brushes. Experimental evidence suggests two ternary adsorption modes: (i) weak, due to nonspecific weak attraction between PEG monomers and the surface of the protein, as exemplified by serum albumin and (ii) strong, due to strong binding of PEG segments to specific protein sites as it occurs for PEG antibodies, which can involve the terminal adsorption of free chain ends or backbone adsorption due to binding to interior chain segments. Ternary adsorption affects the capacity of brushes to repress protein adsorption. The strong adsorption of antibodies can trigger an immune response that may affect the biocompatibility of the surface. Theoretical adsorption isotherms and protein concentration profiles of the three cases are compared for "parabolic" brushes, allowing for the grafting density, 1/Sigma, and degree of polymerization of the PEG chains, N, as well as the volume and surface area of the proteins. The amount of adsorbed protein per unit area, Gamma, exhibits a mode-specific maximum in all three cases. For backbone and weak adsorption, Gamma approximately N, whereas for terminal adsorption, Gamma approximately N0. In every case, the concentration profile of adsorbed proteins, ctern(z), exhibits a maximum at zmax>0 that shifts outward as Sigma decreases; zmax=0 occurs only for weak and backbone adsorption at a high Sigma value.