Silk hydrogels for tissue repair are usually pre-formed via chemical or physical treatments from silk solutions. For many medical applications, it is desirable to utilize injectable silk hydrogels at high concentrations (>8%) to avoid surgical implantation and to achieve slow in vivo degradation of the gel. In the present study, injectable silk solutions that formed hydrogels in situ were generated by mixing silk with low-molecular-weight @entity968 ( @entity970 ), especially PEG300 and 400 (molecular weight 300 and 400gmol(-1)). Gelation time was dependent on the concentration and molecular weight of @entity970 . When the concentration of @entity970 in the gel reached 40-45%, gelation time was less than 30min, as revealed by measurements of optical density and rheological studies, with kinetics of @entity968 faster than PEG300. Gelation was accompanied by structural changes in silk, leading to the conversion from random coil in solution to crystalline b-sheets in the gels, based on circular dichroism, attenuated total reflection Fourier transform infrared spectroscopy and X-ray diffraction. The modulus (127.5kPa) and yield strength (11.5kPa) determined were comparable to those of sonication-induced hydrogels at the same concentrations of silk. The time-dependent injectability of 15% @entity970 -silk hydrogel through 27G needles showed a gradual increase of compression forces from    10 to 50N within 60min. The growth of @entity1 mesenchymal stem cells on the @entity970 -silk hydrogels was hindered, likely due to the presence of @entity970 , which grew after a 5day delay, presumably while the @entity970 solubilized away from the gel. When 5% @entity970 -silk hydrogel was subcutaneously injected in @entity35 , significant degradation and tissue in-growth took place after 20days, as revealed by ultrasound imaging and histological analysis. No significant @entity32 around the gel was observed. The features of injectability, slow degradation and low initial cell attachment suggests that these @entity970 -silk hydrogels are of interest for many biomedical applications, such as anti-fouling and anti-adhesion.

Injectable silk- XXXX hydrogels.

@entity1 :: ('9606', 'Species') :: ['human'] @entity32 :: ('MESH:D007249', 'Disease') :: ['inflammation'] @entity35 :: ('10116', 'Species') :: ['rats'] @entity970 :: ('CHEBI:46793', 'Chemical') :: ['PEG'] @entity968 :: ('MESH:D011092', 'Chemical') :: ['polyethylene glycol', 'PEG400']
@entity968 :: (MESH:D011092,Chemical) :: ['polyethylene glycol']
