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Hydrogels based on cellulose nanofibrils (CNFs) have been widely used as scaffolds for biomedical applications, however, the poor mechanical properties of CNF hydrogels limit their use as ink for 3D bioprinting in order to generate scaffolds for tissue engineering applications. In this study, a dual crosslinkable hydrogel ink composed of a poly(ethylene glycol) (PEG) star polymer and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-oxidized nanocellulose fibers (CNFs) is presented. As the resulting hydrogel had low structural integrity, at first crosslinking of CNFs was introduced by Ca2+. Strong physical interactions between CNFs and Ca2+ cations allowed easy regulation of the viscosity of the inks for extrusion printing raising the solution viscosity by more than 1.5 times depending on the amount of Ca2+ added. The resulting hydrogel had high structural integrity and was further stabilized in a second step by photo crosslinking of PEG under visible light. In only a few seconds, hydrogels with Young's modulus between ∼10 and 30 kPa were obtained just by altering the CNF and Ca2+ content. 3D printed hydrogels supported fibroblasts with excellent cell viability and proliferation. The dual crosslinkable hydrogel ink herein developed is versatile, easy to prepare, and suitable for 3D printing of bioscaffolds with highly tailored viscoelastic and mechanical properties applicable in a wide range of regenerative medicines.

Bioelectronic materials based on conjugated polymers are being developed in the hope to interface with electroresponsive tissues. We have recently demonstrated that a polyaniline chitosan patch can efficiently electro-couple with cardiac tissue modulating its electrophysiology. As a promising bioelectronic material that can be tailored to different types of devices, we investigate here the impact of varying the synthesis conditions and time of the in situ polymerization of aniline (An) on the sheet resistance of the bioelectronic patch. The sheet resistance increases significantly for samples that have either the lowest molar ratio of oxidant to monomer or the highest molar ratio of dopant to monomer, while the polymerization time does not have a significant effect on the electrical properties. Conductive atomic force microscopy reveals that the patch with the lowest sheet resistance has a connected network of the conductive phase. In contrast, patches with higher sheet resistances exhibit conductive areas of lower current signals or isolated conductive islands of high current signals. Having identified the formulation that results in patches with optimal electrical properties, we used it to fabricate patches that were implanted in rats for two weeks. It is shown that the patch retains an electroactive nature, and only mild inflammation is observed with fibrous tissue encapsulating the patch.

In drug therapy, most therapeutic drugs are of low molecular weight and could freely diffuse in the biological milieu depending on the administration route applied. The main reason for the development of polymeric drug carriers is to obtain desired effects such as sustained therapy, local and controlled release, prolonged activity and reduction of side effects. Alternatively, polymeric carriers can be made bioerodible in order to be eliminated by natural ways after a certain time of therapy. Core–shell fibres from coaxial spinneret or emulsion electrospinning are good candidates for the development of such devices; however difficulties remain especially in controlling the release over a sustained period. Here, we present a novel technique combining coaxial and emulsion electrospinning to produce micro-structured core–shell fibres. The design of drug microreservoirs of variable size within the bulk of the fibre combined with a tailored diffusive barrier allows modulating the release kinetics of these novel carriers. A nearly constant and linear release of the model drug Levetiracetam (Mw ≈ 170 g mol−1) from PLGA emulsion-coaxial electrospun fibres is observed over 20 days. This device is aimed to be implanted into the brain for the treatment of epilepsy and is an example of the new capabilities and the promising potential that emulsion-coaxial electrospinning can provide towards the development of future drug carriers.