Kinetic Investigation of Poly(ethylene glycol) Hydrogel Formation via Perfusion‐Based Frontal Photopolymerization: Influence of Free‐Radical Polymerization Conditions on Frontal Velocity and Swelling Gradients

Abstract

Poly(ethylene glycol) diacrylate (PEGDA) hydrogels are extensively used as scaffolds in tissue engineering. The ability to spatially control hydrogel properties is critical for designing scaffolds that direct cell behavior and tissue regeneration. To this end, we have recently developed a polymerization technique, perfusion‐based frontal photopolymerization, to generate tunable gradients in PEG hydrogels. This study explores the effects of polymerization conditions on the velocity of the propagating front and its influence on gradients in hydrogel swelling. Alterations in photoinitiator perfusion rate result in the largest variations in frontal velocity and in the magnitude of the swelling gradient among all polymerization conditions investigated.

Protease-Sensitive Hydrogel Biomaterials with Tunable Modulus and Adhesion Ligand Gradients for 3D Vascular Sprouting

“…Localized and controlled perfusion of a photoinitiator within a monomeric mixture resulted in the establishment of a localized reaction zone and in the formation of a photopolymerizable front that propoagated through the polymer mixture to form cross-linked gradient hydrogel scaffolds upon exposure to visible light. Using this approach, scaffolds with simultaneous gradients in elastic modulus, immobilized RGD concentration, and matrix metalloproteinase (MMP) sensitivity were created, which indiced 3D bidirectional vascular sprout alignment and invasion in culture. ,, The presence of the coupled gradients, however, makes it difficult to clearly elucidate the effects of matrix properties on 3D neovascularization responses. This motivated the development of an alternative, distinct, and robust method to create proteolytically degradable scaffolds with decoupled gradients of initial (i.e., prior material degradation) mechanical properties and immobilized RGD concentration to elucidate their role on vascular sprouting in 3D culture.…”

Role of heat generation and thermal diffusion during frontal photopolymerization

“…Photopolymerization is particularly attractive from a manufacturing perspective because it can be performed at room temperature and in open or controlled atmospheres using readily available UV light sources and commercial monomer or prepolymer formulations [1][2][3]. In practice, photopolymerization has been used in a number of contexts [3], ranging from photolithography [4,5], three-dimensional stereolithography [6], rapid prototyping [7,8], coatings [9], adhesives [10], biomedicine [11], tissue engineering [12,13], and dentistry [14], all of which demonstrate the great versatility of this fabrication method as well as the exciting possibility of manufacturing with light.…”

“…The material properties of the cured solid, e.g., its elastic modulus [18] or refractive index, can be strongly dependent on the conversion fraction φ; therefore, the ability to finely tune the conversion profile is directly relevant to the fabrication of gradient polymer solids having material properties that vary in a systematic manner. Indeed, as demonstrated by Turturro et al [12,13], FPP offers a flexible approach for the controlled production of hydrogel scaffolds with gradient material properties used in tissue engineering. 1.…”

Photoinitiating systems and kinetics of frontal photopolymerization processes – the prospects for efficient preparation of composites and thick 3D structures

“…27 There are publications in the literature focusing on approximating the kinetic basis of the phenomena occurring during the FPP techniques described above. 19,[28][29][30][31][32][33][34] Initiators of radical frontal photopolymerisation When choosing an initiator for FPP, it is necessary to pay attention to several important aspects. First, the appropriate type of initiator for the initiating system is needed.…”