Tissue mimetic hyaluronan bioink containing collagen fibers with controlled orientation modulating cell migration and alignment

Biofabrication is providing scientists and clinicians the ability to produce engineered tissues with desired shapes and gradients of composition and biological cues. Typical resolutions achieved with extrusion-based bioprinting are at the macroscopic level. However, for capturing the fibrillar nature of the extracellular matrix (ECM), it is necessary to arrange ECM components at smaller scales, down to the micron and the molecular level. Herein, we introduce a bioink containing the tyramine derivative of hyaluronan (HA; henceforth known as THA) and collagen (Col) type 1. In this bioink, similar to connective tissues, Col is present in the fibrillar form, and HA functions as a viscoelastic space filler. THA was enzymatically cross-linked under mild conditions allowing simultaneous Col fibrillogenesis, thus achieving a homogeneous distribution of Col fibrils within the viscoelastic HA-based matrix. The THA-Col composite displayed synergistic properties in terms of storage modulus and shear thinning, translating into good printability. Shear-induced alignment of the Col fibrils along the printing direction was achieved and quantified via immunofluorescence and second-harmonic generation. Cell-free and cell-laden constructs were printed and characterized, analyzing the influence of the controlled microscopic anisotropy on human bone marrow-derived mesenchymal stromal cell (hMSC) migration. Anisotropic HA-Col showed cell-instructive properties modulating hMSC adhesion, morphology, and migration from micropellets stimulated by the presence and the orientation of Col fibers. Actin filament staining showed that hMSCs embedded in aligned constructs displayed increased cytoskeleton alignment along the fibril direction. Based on gene expression of cartilage/bone markers and ECM production, hMSCs embedded in the isotropic bioink displayed chondrogenic differentiation comparable with standard pellet culture by means of proteoglycan production (safranin O staining and proteoglycan quantification). The possibility of printing matrix components with control over microscopic alignment brings biofabrication one step closer to capturing the complexity of native tissues.

Photoinduced chitosan–PEG hydrogels with long-term antibacterial properties

The photo-induced synthesis of chitosan–PEG hydrogels with tremendous antibacterial and anti-adhesive properties even after 6 months’ storage.

Eosin-mediated synthesis of polymer coatings combining photodynamic inactivation and antimicrobial properties

Eosin-derived coatings exhibiting photodynamic bacterial inactivation and antibacterial properties.

A specific beta 3-adrenoceptor agonist induces increased pancreatic islet blood flow and insulin secretion in rats

In order to study the role of beta 3-adrenoceptor stimulation on insulin secretion in rats, plasma insulin level and islet blood flow were measured during treatment with CL 316243 which is chemically named disodium (R,R)-5-[2-[[2,3-(3-chlorophenyl)-2-hydroxyethyl]-amino]propyl]-1, 3-benzodioxole-2,2-dicarboxylate, a specific beta 3-adrenoceptor agonist. CL 316243 induced a marked increase in both islet blood flow and plasma insulin concentration without changes in whole pancreatic blood flow. This increase was totally prevented when the rats were pretreated with bupranolol, a beta 1, beta 2, beta 3-adrenoceptor antagonist, but not with nadolol, a beta 1, beta 2-adrenoceptor antagonist. We conclude that beta 3-adrenoceptor stimulation provokes a marked vasodilatation of microvessels in the islets of Langerhans, which in turn could contribute to the increase in insulin secretion.