A technique to create hydrogels with tethered concentration gradients of molecules <i>in vitro</i>

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

• Level A · Stronger Clinical Evidence
• Level B · Emerging clinical evidence with positive signals
• Level C · Early human research exploring benefits
• Level D · Scientific groundwork from lab and animal studies
• Emerging · Emerging topic under active research

Abstract (original English)

This work develops a technique to create and quantify tethered molecular concentration gradients in a hydrogel using a flow chamber. This device is designed to enable isotropic scaffold swelling, nutrient diffusion and real-time microrheological measurements. A hydrogel is first photopolymerized in the flow chamber ensuring that the mechanical properties of the hydrogel across samples are the same prior to molecular concentration gradient creation. Then molecules are passively diffused into the scaffold and a second photopolymerization tethers the concentration gradient into the material. This technique creates in vitro mimics of aspects of biological environments, such as the environment around a hydrogel implanted in the body for cell delivery. We use a well-defined synthetic scaffold with a poly(ethylene glycol) (PEG)-norbornene backbone cross-linked with a matrix metalloproteinase (MMP)-degradable peptide, a standard material for cell encapsulation. The method to tether molecular concentration gradients is validated using a fluorescent PEG-thiol (FITC-PEG-SH), an ideal polymer. We first create a calibration curve by measuring the fluorescence intensity of hydrogels with known uniform concentrations of the tethered fluorescent molecule. The calibration curve is used to calculate spatial concentration from measured fluorescence intensity in hydrogels with polymer or protein c

Evidence level

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

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