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Bioprinting is a recent technology in tissue engineering used for the design of porous constructs through layer-by-layer deposition of cell-laden material. This technology would benefit from new biomaterials that can fulfill specific requirements for the fabrication of well-defined 3D constructs, such as the preservation of cell viability and adequate mechanical properties. We evaluated the suitability of a novel semi-interpenetrating network (semi-IPN), based on hyaluronic acid and hydroxyethyl-methacrylate-derivatized dextran (dex-HEMA), to form 3D hydrogel bioprinted constructs. The rheological properties of the solutions allowed proper handling during bioprinting, whereas photopolymerization led to stable constructs of which their mechanical properties matched the wide range of mechanical strengths of natural tissues. Importantly, excellent viability was observed for encapsulated chondrocytes. The results demonstrate the suitability of hyaluronic acid/dex-HEMA semi-IPNs to manufacture bioprinted constructs for tissue engineering.

The chain stiffness of "native" xanthan (NX) (commercial product of Kelco Inc.), pyruvate-free xanthan (PFX), and acetyl-free xanthan (AFX) has been determined from static light scattering measurements. The Kuhn lengths were determined as being lK = 255 ± 15 nm for NX, 310 ± 40 nm for PFX, and 198 ± 13 for AFX by employing a recently suggested technique of evaluating the angular dependence of the scattered light. The radii of gyration were calculated with these data from the Benoit-Doty equation for polydisperse chains and found to agree within 0.5% of the measured radii. The hydrodynamic radii were derived from measurements of the translational diffusion coefficients by means of dynamic light scattering. Using the mentioned Kuhn lengths and assuming a chain thickness of d = 2.2 nm, we calculated the hydrodynamic radii by the theory of Yamakawa and Fujii. The values were found to be in agreement with the measurement for PFX but about 18% lower for NX and even still 8% lower if d = 5 nm is assumed; for AFX agreement was found with d = 3.3 nm. The time correlation functions (TFC) measured at various angles can be cast into a general shape function <£(Pt), which is only dependent on , where is the first cumulant of the individual TCF's. This shape function follows that of a rigid rod for small and approaches the shape function of a flexible chain for larger , as can be expected for a wormlike chain. Examination of the angular dependence of the first cumulant again reveals intermediate behavior to rigid rods and flexible chains.

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