Glucose-Responsive Boronic Acid Hydrogel Thin Films Obtained via Initiated Chemical Vapor Deposition

Abstract

Glucose-responsive materials are of great importance in the field of monitoring the physiological glucose level or smart insulin management. This study presents the first vacuum-based deposition of a glucose-responsive hydrogel thin film. The successful vacuum-based synthesis of a glucose-responsive hydrogel may open the door to a vast variety of new applications, where, for example, the hydrogel thin film is applied on new possible substrates. In addition, vacuumdeposited films are free of leachables (e.g., plasticizers and residual solvents). Therefore, they are, in principle, safe for in-body applications. A hydrogel made of but-3-enylboronic acid units, a boronic acid compound, was synthesized via initiated chemical vapor deposition. The thin film was characterized in terms of chemical composition, surface morphology, and swelling response toward pH and sucrose, a glucose−fructose compound. The film was stable in aqueous solutions, consisting of polymerized boronic acid and the initiator unit, and had an undulating texture appearance (rms 2.1 nm). The hydrogel was in its shrunken state at pH 4−7 and swelled by increasing the pH to 9. The pK a was 8.2 ± 0.2. The response to glucose was observed at pH 10 and resulted in thickness shrinking.

Recent advances in responsive hydrogels for diabetic wound healing

“…Recently, smart hydrogels with stimulus-responsive functions have attracted considerable attention. Briefly, stimulus-responsive hydrogels can respond to internal physiological signals (i.e., temperature [ 28 , 29 ], pH [ 30 , 31 ], redox [ 32 , 33 ], glucose [ 34 , 35 ], or enzymes [ 36 , 37 ]), external stimuli (i.e., temperature [ 38 , 39 ], magnetic field [ 40 , 41 ], pressure [ 42 , 43 ], reactive oxygen species (ROS) [ 44 , 45 ], light [ 46 , 47 ] and electric field [ 48 , 49 ]) or a combination of the above, which can reversibly or irreversibly change the physical properties or chemical structure ( Fig. 2 ).…”

Advances in surface modification and functionalization for tailoring the characteristics of thin films and membranes via chemical vapor deposition techniques

“…iCVD is one of the most attractive variations of CVD in which a precursor is introduced to the CVD chamber at low pressures and relies on the use of a radical initiator that can be thermally activated at low temperatures and preserving the functionality of the precursor 138,139 . A free‐radical polymerization occurs between the radicals formed by initiator decomposition and monomer species 16 .…”

“…[135][136][137] 4.9 | Initiated CVD iCVD is one of the most attractive variations of CVD in which a precursor is introduced to the CVD chamber at low pressures and relies on the use of a radical initiator that can be thermally activated at low temperatures and preserving the functionality of the precursor. 138,139 A free-radical polymerization occurs between the radicals formed by initiator decomposition and monomer species. 16 During the deposition, substrate is kept at room temperature which is advantageous in utilization of all kinds of substrates including polymeric membranes.…”

Applications of soft biomaterials based on organic and hybrid thin films deposited from the vapor phase

“…Glucose-responsive polymers are at the basis of biosensors that monitor the physiological glucose level and/or regulate insulin delivery. Recently, the first example of a vapor-phase deposited glucose-responsive layer was demonstrated by iCVD [150]. This layer was based on a boronic acid compound.…”