Over the past two decades, hydrogels have come to the
forefront
of tissue engineering and regenerative medicine due to their biocompatibility,
tunable degradation and low immunogenicity. Due to their porosity
and polymeric network built up, it is possible to incorporate inside
drugs, bioactive molecules, or other biochemically active monomers.
Among biopolymers used for the fabrication of functional hydrogels,
silk fibroin (SF) has received considerable research attention owing
to its known biocompatibility and tunable range of mechanical properties.
However, its relatively simple structure limits the potential usability.
One of the emerging strategies is a chemical functionalization of
SF, allowing for the introduction of methacrylate groups. This allows
the versatile processing capability, including photo-cross-linking,
which makes SF a useful polymer as a bioink for 3D printing. The methacrylation
reaction has been done using numerous monomers such as methacrylic
anhydride (MA), 2-isocyanatoethyl methacrylate (IEM), or glycidyl
methacrylate (GMA). In this Review, we summarize the chemical functionalization
strategies of SF materials and their resulting physicochemical properties.
More specifically, a brief explanation of the different functionalization
methods, the cross-linking principles, possibilities, and limitations
of methacrylate compound functionalization are provided. In addition,
we describe types of functional SF hydrogels and link their design
principles to the performance in applications in the broad fields
of biofabrication, tissue engineering, and regenerative medicine.
We anticipate that the provided guidelines will contribute to the
future development of SF hydrogels and their composites by providing
the rational design of new mechanisms linked to the successful realization
of targeted biomedical application.