Versatile lysine dendrigrafts and polyethylene glycol hydrogels with inherent biological properties: in vitro cell behavior modulation and in vivo biocompatibility

Abstract

Poly(ethylene glycol) (PEG) hydrogels have been extensively used as scaffolds for tissue engineering applications, owing to their biocompatibility, chemical versatility and tunable mechanical properties. However, their bio-inert properties require them to be associated with additional functional moieties to interact with cells. We propose here to reticulate PEG molecules with poly(L-lysine) dendrigrafts (DGL) to provide inherent cell functionalities to PEG-based hydrogels. The physico-chemical characteristics of the resulting hydrogels were studied in regard of the concentration of each component. With increasing amounts of DGL, the cross-linking time and swelling ratio could be decreased, conversely to mechanical properties, which could be tailored from 7.7±0.7 to 90±28.8 kPa. Furthermore, fibroblasts adhesion, viability and morphology on hydrogels were then assessed. While cell adhesion significantly increased with the concentration of DGL, cell viability was dependant of the ratio of DGL and PEG. Cell morphology and proliferation, however appeared mainly related to the overall hydrogel rigidity. To allow cell infiltration and cell growth in 3D, the hydrogels were rendered porous. The biocompatibility of resulting hydrogels of different compositions and porosities was evaluated by 3-week subcutaneous implantations in mice. Hydrogels allowed an extensive cellular infiltration with a mild foreign body reaction, histological evidence of hydrogel degradation and neovascularization.

Design and characterization of an in vivo injectable hydrogel with effervescently generated porosity for regenerative medicine applications

“…Moreover, the effervescently porous hydrogel could be injected directly in vivo while eliciting a mild inflammatory reaction with the presence of macrophages degrading hydrogel walls as previously shown for DGL/PEG systems [35]. The local blood flow around the injected implants and the hydrogel water content are hypothesized to help the diffusion and solubility of CO 2 gas generated by effervescence in the bloodstream and biological tissues, preventing the formation of a gas cavity.…”

“…However, in the case of injected effer-vescent porous hydrogels, the DGL is sufficiently sequestrated inside the network to prevent cell mortality in direct contact. As a result, the inherent cell-interaction properties of the DGL/PEG hydrogels (brought by the DGL amine residues [35]) are conserved and cells can attach, spread and proliferate on the porous hydrogels surface without any washing or post formulation treatments. Of particular interest, cell behaviour and morphology could still be modulated through the conserved ability to tune the DGL/PEG hydrogels mechanical properties by varying their compositions.…”

“…The effect of DGL/PEG mechanical and biochemical versatility on cells [35] was thus preserved in the EPH settings.…”

“…These conditions are present in our candidate formulations, based on recently developed poly (L-lysine) dendrimers (DGL) and Nhydroxysuccinimide (NHS) bi-functionalized polyethylene glycol (PEG) hydrogels, which present the advantages of a swift and tailorable crosslinking (seconds to minutes), extensively controllable mechanical properties (from 8 to 90 kPa), inherent interactions with cells through polycationic charges brought by the DGL and biocompatibility [35,36]. Thus we hypothesized that the introduction of potassium carbonate (Pc) and glacial acetic acid (Gaa) as CO 2 producers in the DGL/PEG hydrogels' precursors, to allow an effervescent reaction to occur, could be a facile strategy enabling the formation of a porosity inside DGL/PEG hydrogels while preserving their injectable and mechanical versatility potential as illustrated in Fig.…”

Controlled Polyelectrolyte Association of Chitosan and Carboxylated Nano-Fibrillated Cellulose by Desalting

“…In the case of chitosan-rich systems, nanofibrillated cellulose-reinforced chitosan hydrogels were successfully obtained using a weakly charged nanocellulose and ultrasonic treatment of a pre-mixture to ensure a satisfactory dispersion of the nanofibrils within the chitosan solution, before gelation of chitosan with a base [ 31 , 32 ]. The possibility to tune the mechanical properties of hydrogels, at subcellular scale, with the possibility to prepare soft materials in a wide elastic modulus range appears to be key to control the fate of cells at their contact [ 37 ], since cell phenotype may be impacted by the mechanical cues of their micro-environment. The stretching and drying of such nanocomposite hydrogels yields solid materials with inherited improved mechanical properties, in particular in the case of yarns [ 38 ].…”