Biodegradable Polyanhydrides as Encapsulation Layers for Transient Electronics

Abstract

Bioresorbable electronic systems represent an emerging class of technology of interest due to their ability to dissolve, chemically degrade, disintegrate, and/or otherwise physically disappear harmlessly in biological environments, as the basis for temporary implants that avoid the need for secondary surgical extraction procedures. Polyanhydride‐based polymers can serve as hydrophobic encapsulation layers for such systems, as a subset of the broader field of transient electronics, where biodegradation eventually occurs by chain scission. Systematic experimental studies that involve immersion in phosphate‐buffered saline solution at various pH values and/or temperatures demonstrate that dissolution occurs through a surface erosion mechanism, with little swelling. The mechanical properties of this polymer are well suited for use in soft, flexible devices, where integration can occur through a mold‐based photopolymerization technique. Studies of the dependence of the polymer properties on monomer compositions and the rates of permeation on coating thicknesses reveal some of the underlying effects. Simple demonstrations illustrate the ability to sustain operation of underlying biodegradable electronic systems for durations between a few hours to a week during complete immersion in aqueous solutions that approximate physiological conditions. Systematic chemical, physical, and in vivo biological studies in animal models reveal no signs of toxicity or other adverse biological responses.

Wirelessly controlled, bioresorbable drug delivery device with active valves that exploit electrochemically triggered crevice corrosion

“…Figure 1A highlights the design aspects and key materials for a simple system of this type, consisting of a polymer reservoir, a wireless power harvester, and a metal gate valve. Polybutanedithiol 1,3,5-triallyl-1,3,5-triazine-2,4,6(1 H ,3 H ,5 H )-trione penteonic anhydride (PBTPA), a bioresorbable polyanhydride ( 13 ), serves as a substrate and a containment vessel for an aqueous drug of interest. Synthesis of the PBTPA relies on thiol-ene click reactions of three compounds initiated by exposure to ultraviolet (UV) light: 4-pentenoic anhydride (4PA), 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT), and 1,4-butanedithiol.…”

“…Preparation of the materials began with mixing of 4-PA, TTT, and 1,4-butanedithiol with a molar ratio of 1:4:7 (PBTPA 1:4:7) or 1:1:2.5 (PBTPA 1:1:2.5) in polydimethylsiloxane (PDMS) molds. Initiating a thiol-ene click reaction by adding photoinitiator (5 weight %) and exposing to UV light (λ = 365 nm) formed PBTPA for the bioresorbable reservoirs ( 13 ). Wet etching of foils (Mg foil, 10 to 50 μm thick; or Mo foil, 10 μm thick) yielded bioresorbable metal electrodes.…”

A Review: Electrode and Packaging Materials for Neurophysiology Recording Implants

“…However, it must be noted that some applications only require stable biotic-abiotic interfaces for a certain period of time (Muskovich and Bettinger, 2012 ; Lu et al, 2020 ). In the area of biodegradable encapsulation, Choi et al ( 2020 ) demonstrated a bioresorbable polyanhydride-based polymer (PBTPA). The result shows PBTPA film has good biocompatibility, low swelling during dissolution in water, mechanical properties supporting robust operation in flexible devices, and good processability potential.…”

Stretchable, dynamic covalent polymers for soft, long-lived bioresorbable electronic stimulators designed to facilitate neuromuscular regeneration

“…As shown in Fig. 2a , extending the in vivo operational lifetime of bioresorbable electronic stimulators from a few days to several months demands solutions to daunting challenges in materials science and device design that follow directly from requirements that the system must be (1) electrically reliable in operation, with minimal permeation of biofluids and parasitic leakage of current 26 – 30 , (2) mechanically robust under various deformations, including stretching, twisting and bending, during natural motions 31 , (3) completely dissolvable (i.e., bioresorbable), at the materials level, without adverse effect 32 , and (4) entirely biocompatible during and after the treatment duration 23 . The operational lifetimes reported here are significantly longer than those of previously reported flexible or stretchable bioresorbable devices, where the operation is limited typically to a few days (Supplementary Note 2 ) 15 , 33 – 35 .…”