Simplifying Molecular Transport in Polyelectrolyte Multilayer Thin Films

Abstract

The matrix properties of polyelectrolyte multilayer thin films (PEM) are critical in making them a viable candidate for various biomedical applications. The location and ability of molecules to diffuse through the PEM architecture determines their encapsulation and release capabilities in a given matrix for various biomedical applications. The main aim of this review article is to provide a complete understanding of molecular transport on the surface as well as across the bulk of the PEM matrix. Different physiochemical strategies to promote or suppress the diffusivity of various molecules inside the PEM are mentioned in brief. A set of guiding principles is uncovered for getting a complete picture of loading and release of molecules across the PEM structure, which can play a key role in designing a desirable PEM assembly and have important implications for designing multicomponent, targeted and controlled drug‐delivery vehicles. Understanding the molecular diffusivity in PEM stack at the nano and micro scales will help to design superior host materials for biomedical engineering applications.

Fluorescence Signal Enhancement by a Spray-Assisted Layer-by-Layer Technique on Aluminum Tape Devices for Biosensing Applications

“…However, in the experimental results, diffusion of fluorophores and the effective fluorescence modulation were a combination of the fluorophores residing on top as well as diffused fluorophores. A similar observation of damping was reported in our previous finding by Pahal et al, and the drive for this kind of diffusion behavior will be attributed to factors like the nature of the polyelectrolyte, salt/ionic environment, size of the adsorbed molecule, cross-linking chemistry, etc …”

“…A similar observation of damping was reported in our previous finding by Pahal et al, 23 and the drive for this kind of diffusion behavior will be attributed to factors like the nature of the polyelectrolyte, salt/ionic environment, size of the adsorbed molecule, cross-linking chemistry, etc. 54 The three-dimensional porous model has been experimentally verified by incubating 1 μg/mL FITC−biotin on Al-tape-(PAH/ PAA) n+0.5 devices for 0.5 ≤ n ≤ 20.5, fabricated by SP-LbL, DA-LbL, and SA-LbL techniques. A similar experiment was also performed by incubating FITC−biotin on (Si/SiO 2 )/PAH films of SiO 2 thickness (t) in the range of 0 < t < 200 nm, which ensures the fluorescence enhancement as a result of adsorption of biomolecules only on the surface in two dimensions.…”

Fast‐Dip Layer‐by‐Layer Self‐Assembly of Polyelectrolytes as a Low‐Cost Biosensing Platform

“…Although the PEM stack/film characteristics depend on the fabrication parameters like pH, ionic strength, and molecular weight of polyelectrolytes, the dipping and rinsing time also play an essential role in defining the finalized PEM stack. [ 7–14 ] LbL self‐assembly of PEM happens by dip, spin, and spray‐based deposition techniques. Conventional dip (CDip)‐based LbL self‐assembly occurs by dipping the desired substrate in polyelectrolyte solution for ≈10–15 min, followed by rinsing steps of 3+1+1 min.…”

“…[ 37,38 ] During the PEM film buildup, molecular diffusion within the films has dominant implications on deposition time. [ 14 ] Interdiffusion of the constituent molecules impacts the film structure, growth, thickness, and physicochemical properties of PEM. [ 39–41 ] Picart et al.…”

“…[37,38] During the PEM film buildup, molecular diffusion within the films has dominant implications on deposition time. [14] Interdiffusion of the constituent molecules impacts the film structure, growth, thickness, and physicochemical properties of PEM. [39][40][41] Picart et al have reported that the exponential growth in PEM is due to the rapid onset of the interdiffusion during the film buildup.…”