Voltaglue Bioadhesives Energized with Interdigitated 3D‐Graphene Electrodes

Abstract

Soft tissue fixation of implant and bioelectrodes relies on mechanical means (e.g. sutures, staples, screws), with associated complications of tissue perforation, scarring, and interfacial stress concentrations. Adhesive bioelectrodes address these shortcomings with voltage cured carbene-based bioadhesives, locally energized through graphene interdigitated electrodes.Electro-rheometry and adhesion structure activity relationships were explored with respect to voltage and electrolyte on bioelectrodes synthesized from graphene 3D-printed onto resorbable polyester substrates. Adhesive leachates effects on in vitro metabolism and human derived platelet rich plasma response serves to qualitatively assess biological response. The voltage activated bioadhesives are found to have gelation times of 60 sec or less with maximum shear storage modulus (G') of 3 kPa. Shear modulus mimics reported values for human soft tissues (0.1-10 kPa). The maximum adhesion strength achieved for the ~50 mg bioelectrode films is 170 g cm -2 (17 kPa), which exceeds the force required for tethering of electrodes on dynamic soft tissues. The method provides the groundwork for implantable bio/electrodes that may be permanently incorporated into soft tissues, vis-à-vis graphene backscattering wireless electronics since all components are bioresorbable.

Precise Control of Diazirine Reduction to Tune the Mechanical Properties of Electrocuring Adhesives

“…The level of grafting and the quantification of the diazirine molecules conjugated to the PAMAM dendrimer has been verified more precisely in the past with size exclusion chromatography (SEC) connected in series to UV/Vis, multiangle laser light scattering, and refractive index detectors. [22,26,30] A solid correspondence between the theoretical conjugation level from the stoichiometric calculations and the experimental value was demonstrated. [24] SEC multi-detector analysis, as reported previously, ensured that only grafted diazirine is present on VG.…”

“…Synthesis and structure-property relationships of voltage, current, electrode design, DC/AC signals, cation, and temperature on viscoelastic properties have been previously reported. [22,26,28,[30][31][32] Electric fields are hypothesized to reduce diazirine to a reversible and semi-stable diazirinyl radical (t 1 = 2 = 46 s), that then transitions to a shortlived (6 ns) carbene intermediate. [22,26] The primary evidence supporting this mechanism is diazirine decay, nitrogen gas emission, and rheological viscoelastic transition from viscous to elastic stress deformation (aka gelation) of the high solute (� 50 %) PAMAM-diazirine formulations.…”

Structure–Activity Relationships of Voltaglue Organic Blends

“…Voltaglue, a diazirine‐grafted PAMAM dendrimer (G5‐Dz), serves as a model system in the field of carbene‐based bioadhesive research to investigate and develop adhesives that cure under low voltage. [ 1 ] Crosslinking in Voltaglue can be initiated with diverse electrode geometries such as disposable three‐electrode chips, [ 1,2 ] bioresorbable interdigitated 3D‐graphene electrodes (IDE), [ 3 ] and semiconductive substrates. [ 4 ] Despite these advances, Voltaglue has some limitations (when stimulated/electrocured) in aqueous environments: 1) it displays low storage modulus (1 kPa) in comparison to photo‐ and thermal‐curing (100 kPa) and 2) the water electrolysis that takes place at –1.3 V may lead to excessive foaming.…”

Pulsed Laser Activation of Carbene Bioadhesive Boosts Bonding Strength

“…By grafting TAD onto G5 PAMAM dendrimer, a model system is easily synthesized in a one‐step reaction to explore photochemical and bioadhesive structure–activity relationships. Previous investigations have explored PDz with respect to grafting/solid content, voltage‐activation, and non‐aqueous formulations . Previous studies have also focused on biocompatibility and cytotoxicity behavior of the primary components.…”