Bacterial cellulose (BC) possesses the desirable properties of biocompatibility, high porosity, high surface area and noticeable mechanical strength as a scaffold in bone tissue engineering. However, the lack of osteogenic activity restricts its application. In this study, gold nanoparticles (GNPs) with excellent osteogenic differentiation ability were incorporated into the network of BC hydrogel (Au/BC hydrogels) by the in-situ fermentation. The effects of GNPs on physicochemical properties of BC hydrogel and subsequently in vitro osteogenic differentiation and in vivo bone regeneration of Au/BC hydrogels were comprehensively investigated. The results showed that the increased feeding amounts of GNPs could remarkablly enhance the Au/BC hydrogels with better mechanical properties, higher porosity, larger surface area, and biocompatibility. The sustainable release of GNPs endowed the hydrogels with an outstanding biological activity in facilitating osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Mechanism research showed that autophagy might be a potential pathway for Au/BC hydrogels-induced osteogenic differentiation of hBMSCs. In addition, Au/BC hydrogel exhibited an excellent in vivo bone repair performance in a rabbit model of femoral defect, which was evidenced by the significant newly bone formation. Overall, the multifunctional Au/BC hydrogels fabricated by in-situ fermentation could serve as a good scaffold for promoting bone tissue regeneration in clinic. • Gold nanoparticles (GNPs) with excellent osteogenic differentiation ability were incorporated into the network of BC hydrogelby the in-situ fermentation. • The developed hydrogels demonstrated desirable mechanical properties, sustainable release ability of GNPs, favorable biocompatibility and excellent osteogenic activities. • Mechanism research revealed that autophagy might play a vital role in osteogenic differentiation of hBMSCs treated with Au/BC hydrogels. • The incorporation of GNPs into hydrogels remarkably improved the bone regeneration performance in vivo. 

Biofabrication of natural Au/bacterial cellulose hydrogel for bone tissue regeneration via in-situ fermentation

Today, sustainable and natural resources including biowastes have been considered attractive starting materials for the fabrication of biocompatible and biodegradable carbon dots (CDs) due to the benefits of availability, low cost, biorenewability, and environmentally benign attributes. These carbonaceous nanomaterials have been widely explored in the field of sensing/imaging, optoelectronics, photocatalysis, drug/gene delivery, tissue engineering, regenerative medicine, and cancer theranostics. Designing multifunctional biowaste-derived CDs with a high efficacy-to-toxicity ratio for sustained and targeted drug delivery, along with imaging potentials, opens a new window of opportunity toward theranostic applications. However, crucial challenges regarding the absorption/emission wavelength, up-conversion emission/multiphoton fluorescence mechanisms, and phosphorescence of these CDs still need to be addressed to attain the maximum functionality and efficacy. Future studies ought to focus on optimizing the synthesis techniques/conditions, evaluating the influence of nucleation/growth process on structures/properties, controlling their morphology/size, and finding the photoluminescence mechanisms. Reproducibility of synthesis techniques is another critically important factor that needs to be addressed in the future. Herein, the recent developments related to the biowaste-derived CDs with respect to their biomedical applications are deliberated, focusing on important challenges and future perspectives.

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Biowaste-Derived Carbon Dots: A Perspective on Biomedical Potentials

Designing a novel bio-compatible hydroxyapatite (HA)/hydroxyquinoline (8-HQ)-inbuilt polyvinylalcohol (PVA) composite coatings on Mg AZ31 implants via electrospinning and immersion protocols: smart anti-corrosion and anti-bacterial properties reinforcements

Novel composite hydrogels representing interpenetrating polymeric networks (IPN) have been synthesized and consisted of Gluconacetobacter xylinus cellulose (GxC) and poly-1-vinyl-1,2,4-triazole (PVT) with Cu2⁺. The composite hydrogels’ mesostructure has been studied from 1.6 ​nm to 2.5 ​μm by small-angle and ultra-small-angle neutron scattering methods. It has been found that IPN complexes have three types of inhomogeneities: GxC, PVT, and PVT complex with Cu2⁺. The amount of the absorbed ions can be tuned as confirmed by electron paramagnetic spectroscopy. Besides, three hierarchy levels of GxC remained in the supramolecular structure of composite hydrogels. Reveling structure formation in these composite hydrogels is essential in fabricating hybrid polymeric materials for regenerative medicine, involving antibacterial or antifungal applications. 

Novel biocompatible Cu2+-containing composite hydrogels based on bacterial cellulose and poly-1-vinyl-1,2,4-triazole

https://doi.org/10.1016/j.bioactmat.2022.12.014

Nanomaterial-assisted theranosis of bone diseases

Additive manufacturing, also known as 3D-printing, has been successfully employed to create novel bioactive scaffolds incorporating carbon dots for bioimaging purposes. Fused filament fabrication technique (FFF) was used to print a hybrid poly-lactic acid (PLA)-based filament bearing bioactive material, suited for hydroxyapatite (HAp) development, as well as carbon dots which by virtue of their strong luminescence could support an optical characterization of the composite, thus, its regenerative stages. This technique using FFF biodegradable PLA can be used to create the exact custom-made scaffold depending on the user needs (i.e. shape of a bone fracture), whereas the bioactive material (bioglass® 45S5) assists bone regeneration by HAp development. On the other hand, biocompatible red emissive boron-doped carbon dots could allow for monitoring of the procedure. Scaffolds were tested for their in vitro bioactivity by soaking in simulated body fluid (SBF) solution. In addition, in vitro cytotoxicity testing confirmed the low toxicity of the composite materials used for creating the scaffolds. Degradation of the PLA scaffold initiated immediately providing space for bone regeneration. HAp development was confirmed by scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM/EDS) and infrared spectroscopy (IR). Ultraviolet visible and photoluminescence spectroscopies were used to evaluate the properties of the carbon dots as well as composite materials. Results indicate that this is a promising technique for confronting asymmetric or irregular-shaped bone fractures with simultaneous monitoring of the healing process through bioimaging.

Athanasia Saranti

Papers

3D-printed bioactive scaffolds for bone regeneration bearing carbon dots for bioimaging purposes