Abstract
As one kind of “smart” material, thermogelling polymers find applications in biofabrication, drug delivery and regenerative medicine. In this work, we report a thermosensitive poly(2-oxazoline)/poly(2-oxazine) based diblock copolymer comprising thermosensitive/moderately hydrophobic poly(2-N-propyl-2-oxazine) (pPrOzi) and thermosensitive/moderately hydrophilic poly(2-ethyl-2-oxazoline) (pEtOx). Hydrogels were only formed when block length exceeded certain length (≈100 repeat units). The tube inversion and rheological tests showed that the material has then a reversible sol-gel transition above 25 wt.% concentration. Rheological tests further revealed a gel strength around 3 kPa, high shear thinning property and rapid shear recovery after stress, which are highly desirable properties for extrusion based three-dimensional (3D) (bio) printing. Attributed to the rheology profile, well resolved printability and high stackability (with added laponite) was also possible. (Cryo) scanning electron microscopy exhibited a highly porous, interconnected, 3D network. The sol-state at lower temperatures (in ice bath) facilitated the homogeneous distribution of (fluorescently labelled) human adipose derived stem cells (hADSCs) in the hydrogel matrix. Post-printing live/dead assays revealed that the hADSCs encapsulated within the hydrogel remained viable (≈97%). This thermoreversible and (bio) printable hydrogel demonstrated promising properties for use in tissue engineering applications.
Highlights
Recent innovations in biomaterials have had a huge impact on all aspects of tissue engineering, regenerative medicine and drug delivery, resulting in development of “smart”biomaterials [1,2]
Few reports investigated the thermogelation of pure POx or POx/POzi based systems [6,47,48,60,63]
Hydrogel formation was only observed when the pEtOx had extremely high degree of polymerization (DP) [63], in contrast for pPrOzi-b-pMeOx diblock, the gelation was observed at much lower DP [47]
Summary
Recent innovations in biomaterials have had a huge impact on all aspects of tissue engineering, regenerative medicine and drug delivery, resulting in development of “smart”biomaterials (responsive to external stimuli, e.g., temperature, pH, light etc.) [1,2]. A thermogel is a stimuli-responsive “smart” material which responds to change in temperature, above or below the critical temperature by a (typically reversible) sol-gel transition. In the majority of cases, the transition takes place upon increase in temperature [4] but inverse gelation has been observed [5,6,7]. These are highly versatile materials and repetitively proposed for multiple applications in biomedical, pharmaceutical and food industry. Poly(N-isopropylacrylamide) [10,11] and few members of Pluronics® family ( known as poloxamers)
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