Nafion in Biomedicine and Healthcare

Abstract

Nafion has long been recognized as the gold standard for proton exchange membranes, due to its exceptional ion exchange capacity and its advanced performance in chemically aggressive environments. In recent years, a growing body of evidence has demonstrated that Nafion is equally well-suited in complex biological conditions owing to its structural robustness, responsive functionality and intrinsic biocompatibility. These characteristics have enabled its transition into the biomedical and healthcare sectors, where it is currently being explored for a diverse and expanding range of applications. To that end, Nafion has been systematically investigated as a key component in bioelectronic systems for energy harvest, sensors, wearable electronics, tissue engineering, lab-on-a-chip platforms, implants, controlled drug delivery systems and antimicrobial surface coatings. This review examines the distinctive structural and electrochemical characteristics that underpin Nafion's performance in these biomedical contexts, provides an overview of recent advancements, emphasizes critical performance metrics and highlights the material's growing potential to shape the future of biomedical technology.

Keywords: Nafion; antimicrobial; bioelectronic system; biomedicine; biosensors; controlled drug delivery; electrochemical characteristics; healthcare; ion exchange capacity; lab-on-a-chip; proton exchange membrane.

Figure 1

(a) Energy generation via reverse electrodialysis that relies on the use of Nafion (b) as the cation exchange membrane (CEM) and exploits the ionic gradient between the gastric mucous and the gastric juice (c). Adopted from reference [25].

Figure 2

(a) Selectivity and (b) cycle stability of Nafion-based HCHO sensor. (c) Sensor’s response to healthy individuals and simulated lung cancer patients. Adopted from reference [31].

Figure 3

Glial fibrillary acidic protein (GFAP) immunoreactivity in cortical astroglia following reference electrode removal. (i) Fluorescence microscopy images depict the tissue surrounding the implantation site of (A) a bare Ag/AgCl reference electrode and (B) a Nafion-coated electrode after 14 days. (ii) Bright-field images show GFAP immunoreactivity around representative lesion sites for bare (top) and Nafion-coated (bottom) electrodes at 7 days (C), 14 days (D), and 28 days (E) post-implantation, demonstrating differences in glial activation over time. Adopted from reference [38].

Figure 4

(a) Representative amperometric responses of the Nafion-coated NdNiO glutamate biosensor recorded at an applied potential of 0.6 V vs. Ag/AgCl in 0.01 M Phosphate-buffered saline (pH = 7.4), both in the presence and absence of Glutamate Oxidase (GluOx). (b) The corresponding calibration plots demonstrate a linear relationship between current density and glutamate concentration. Adopted from reference [40].

Figure 5

(a) Photograph of melt-spun PEDOT:Nafion fibers, wrapped around a 5 mm wide syringe cover. The evolution of electrical conductivity in PEDOT:Nafion fibers was evaluated during uniaxial stretching up to the point of mechanical failure (b) and during cyclic deformation within the elastic regime (c). Adopted from reference [41].

Figure 6

(a) The components of a voltammetric smartwatch, which can render APAP readouts. Nafion/H-BDDE-enabled ex situ APAP quantification in sweat. (b) Sensor-measured APAP concentration in the sweat of a human subject, collected before and at intermittent time points after the oral administration of a medication containing 650 mg APAP. (c) Sensor-measured APAP concentrations in saliva sweat samples versus the corresponding LC-MS/MS readouts. Adopted from Reference [42].

Figure 7

(a) Schematic description of a protein preconcentration chip integrating a Nafion strip demonstrating the buffer and the sample channels and the corresponding voltages (V_b and V_L/V_H, respectively). The magnified view highlights the guiding channel designed for precise Nafion strip placement. (b) Fluorescence images showing preconcentration of 6 nM AF-BSA at 1, 5, 9, and 11 min after applying 10 V (V_H = 15 V, V_L = 5 V); buffer reservoirs held at 0 V. Adopted from Reference [47].

Figure 8

(a) Temperature sweeps (ω = 1 rad/s, strain amplitude = 2%) for aqueous gels containing 32.5 wt% E₁₉P₆₉E₁₉ in the absence (●, black) and presence of 5 wt% Nafion (▲, red) and 10 wt% Nafion (■, blue). Solid symbols represent storage modulus (G′), and open symbols represent loss modulus (G″). Inset: Photograph of the 32.5 wt% E₁₉P₆₉E₁₉/10 wt% Nafion gel at 40 °C under UV light (fluorescent dye added for visualization). (b) Release profiles of ibuprofen from 32.5 wt% E₁₉P₆₉E₁₉ in the absence (●, black) and presence (■, blue) of 10 wt% Nafion in phosphate-buffer solution (pH 7.4) at 37 °C. Adopted from Reference [57].

Figure 9

(A) ¹H MR image of an agar phantom containing Nafion based nanocarriers. (B) Corresponding ¹⁹F MR image. (C) Overlay of the ¹H and ¹⁹F MR images. Adopted from Reference [63].

Figure 10

(a) 3D confocal laser scanning microscopy (CLSM) images showing the exclusion zone (EZ) at the Nafion–bacteria suspension interface for three pathogenic strains: E. coli, L. monocytogenes, and S. aureus. (b) Normalized pixel intensity (NPI) profiles indicate near-zero cell density within the first 25 μm from the Nafion–triptic soy broth (TSB) interface, a sharp increase between 25 and 50 μm, gradual decline after 80 μm, and a plateau beyond 150 μm. Adopted from reference [65].

Figure 11

(a) Photographs of Petri dishes containing E. coli cultures. The left side shows exposure to uncoated crystals, while the right side shows exposure to (Naf/GO–NH₂)₅-coated disks under identical conditions. (Images are composites of two separate Petri dishes.) (b) Percent reduction in E. coli and S. aureus populations after exposure to Nafion, (Naf/GO–NH₂)₅, and thermally annealed-(Naf/GO–NH₂)₅ coated crystals. Adopted from Reference [67].