Polyelectrolyte multilayers as coatings for membrane separation

Transport of Proteins through polyelectrolyte Multilayer membranes : Design of a single step process for the purification of proteins. This study mainly deals with the investigation of transport characteristics of model protein (bovine serum albumin) and egg white proteins ovalbumin and lysozyme through multilayer membranes.

(Usha K. Aravind et al., Journal of Membrane Science 299 (2007) 146–155)
(Usha K. Aravind et al., Journal of Membrane Science 325 (2008) 625–632)

The design of bioactive surfaces (either protein adhesive or protein repellant) has been a challenging task for the past few decades as these are desirable for applications that include protein separation, purification, biosensors and controlled release. Surface modification by layer-by-layer assembly of polyelectrolytes can be employed for the fine tuning of biocompatibility of surfaces. . In this work an attempt is made to understand layer dependent protein adhesive/repellence nature of polyelectrolyte multilayer. This study also focuses on the possible biofunctionalization under pressure driven Condition.

Schematic representation of BSA adsorption to (a) 3 and 5 bl (Simple adsorption and Ultrafiltration conditions); (b) Repellence at 7th bl (UF conditions). (Usha K. Aravind et al., Colloids and Surfaces B: Biointerfaces 94 (2012) 118– 124).

Polyelectrolyte multilayer build up is used extensively for the modification and functionalization of surfaces. The surface structure and composition can be well tuned on a nanometer scale by the control over construction parameters. The embedded biomolecules can show properties / enhanced properties as the matrix provides a very high ratio of surface area to volume. This property is utilized to create sensors for molecules such as hydrogen peroxide, mercuric chloride, etc.,

Usha K. Aravind et al., Analytical Biochemistry, 2013 In Press, Accepted Manuscript, Available online

Novel composite membranes with tunable ultra thin, highly selective separation layer is obtained by layer-by-layer (LbL) assembly of cationic and anionic polyelectrolytes on porous substrates. Polyelectrolyte multilayers (PEM) can act as a shell that can form open and closed structures at varying pH. This property enables the complete recovery of the adsorbed dyes and their reuse under specific pH. The removal efficiency of multilayered membranes are investigated using model textile effluents and industrial textile and paper mill effluent. The uptake of dye was found to be very much dependent on the type of bilayers

(Usha K. Aravind et al., Desalination, 252 (2010) 27–32 Usha K. Aravind et al., Desalination, 288 (2012) 72–79)

Modified membrane support in ion separation has gained momentum in water purification as they possess high rejection capacity. The low pressure driven membrane separation process has an upper hand in water purification with the introduction of thin film assemblies on conventional ultrafiltration/microfiltration membranes. Schematic representation of transport of Cl-/H2PO4- through PEI/PSS multilayers (Usha K. Aravind et al., Langmuir 2012, 28, 12744−12752)

The global need for clean and sustainable energy is ever increasing and electrochemical devices such as fuel cells, batteries, and solar cells show great potential. A major component of these devices is an ion-conducting electrolyte which enables fast charge transport between electrodes. Direct methanol fuel cell (DMFC), using liquid methanol directly as a fuel feed is used as an alternative source of power. It has an upper edge due to portability though it suffers from a poor oxidative reaction of the catalyst at anode, and methanol cross over that causes fuel losses. Nafion, the traditionally used membrane for PEM fuel cell exhibits excellent proton conductivity, high mechanical strength, and good chemical electrochemical stability. However, due to the relatively high price and high methanol crossover of 40%, the development of new proton conducting materials for DMFC is on the lookout.

Fluorescence spectroscopy is a widely applied technique to study the protein-drug binding and the conformational changes associated with the binding process. Serum albumins are widely employed for studying protein folding or ligand binding and several methods are used to monitor the conformational changes during the interaction. The intrinsic fluorescence of proteins is monitored to study the binding processes. Tryptophan residues present in proteins are sensitive to environmental changes taking place during the interaction. Drugs from different classes (antihypertension formulation/diuretics, drugs for inflammatory bowel diseases, Anticancer agents, Antimalarial agents, vitamins etc.) are used to understand the mechanism of interaction. Forster’s theory of non radiative energy transfer (FRET) is useful in calculating the distance between donor and acceptor pair. The same technique is applied in the protein-drug system with a speculation that this would provide useful information regarding the effectiveness of the binding interactions. The conformational changes of proteins are studied using combined circular dichroism, synchronous fluorescence and FTIR techniques. The excited state dynamics of the drug-protein interaction are also evaluated to monitor the interaction between proteins and small molecules and to probe the structural and dynamic changes during the binding process. The spectroscopic and photo physical data of these molecules in homogeneous and micro heterogeneous media are expected to be helpful for a better understanding of the nature of binding and bio distribution of these drugs inside the living cells.