3D Bioprinted Xanthan Hydrogels with Dual Antioxidant and Chondrogenic Functions for Post-traumatic Cartilage Regeneration.

Intra-articular trauma typically initiates the overgeneration of reactive oxidative species (ROS), leading to post-traumatic osteoarthritis and cartilage degeneration. Xanthan gum (XG), a branched polysaccharide, has shown its potential in many biomedical fields, but some of its inherent properties, including undesirable viscosity and poor mechanical stability, limit its application in 3D printed scaffolds for cartilage regeneration. In this project, we developed 3D bioprinted XG hydrogels by modifying XG with methacrylic (MA) groups for post-traumatic cartilage therapy. Our results demonstrated that the chemical modification optimized the viscoelasticity of the bioink, improved printability, and enhanced the mechanical properties of the resulting scaffolds. The XG hydrogels also exhibit decent ROS scavenging capacities to protect stem cells from oxidative stress. Furthermore, XGMA(H) (5% MA substitution) exhibited superior chondrogenic potential in vitro and promoted cartilage regeneration in vivo. These dual-functional XGMA hydrogels may provide a new opportunity for cartilage tissue engineering.

Tetramethylphosphinane as a new secondary phosphine synthon.

Secondary phosphines are important building blocks in organic chemistry as their reactive P-H bond enables construction of more elaborate molecules. In particular, they can be used to construct tertiary phosphines that have widespread applications as organocatalysts, and as ligands in metal-complex catalysis. We report here a practical synthesis of the bulky secondary phosphine synthon 2,2,6,6-tetramethylphosphinane (TMPhos). Its nitrogen analogue tetramethylpiperidine, known for over a century, is used as a base in organic chemistry. We obtained TMPhos on a multigram scale from an inexpensive air-stable precursor, ammonium hypophosphite. TMPhos is also a close structural relative of di-tert-butylphosphine, a key component of many important catalysts. Herein we also describe the synthesis of key derivatives of TMPhos, with potential applications ranging from CO2 conversion to cross-coupling and beyond. The availability of a new core phosphine building block opens up a diverse array of opportunities in catalysis.

Nano-Strategies for Lignin Biomaterials toward Cancer Therapy.

Lignin is a nontoxic and biocompatible biopolymer with many promising characteristics, including a high tensile strength and antioxidant properties. This natural polymer can be processed through several chemical methods and modified into lignin nanomaterials for potential biomedical applications. This review summarizes the latest developments in nanolignin (NL)-based biomaterials for cancer therapy; various NL applications related to cancer therapy are considered, including drug and gene delivery, biosensing, bioimaging, and tissue engineering. The manuscript also outlines the potential use of these materials to improve the therapeutic potency of chemotherapeutic drugs by decreasing their dose and reducing their adverse effects. Due to its high surface area-to-volume ratio and the easy modification of its chemical components, NL could serve as an appropriate matrix for the binding and controlled release of various pharmaceutical agents. Moreover, the challenges in the utilization of NL-based materials for cancer therapy are discussed, along with the prospects of advances in such nanomaterials for medical research applications.

Hydrogel-Based Flexible Electronics.

Flexible electronics is an emerging field of research involving multiple disciplines, which include but not limited to physics, chemistry, materials science, electronic engineering, and biology. However, the broad applications of flexible electronics are still restricted due to several limitations, including high Young's modulus, poor biocompatibility, and poor responsiveness. Innovative materials aiming for overcoming these drawbacks and boost its practical application is highly desirable. Hydrogel is a class of 3D crosslinked hydrated polymer networks, and its exceptional material properties render it as a promising candidate for the next generation of flexible electronics. Here, the latest methods of synthesizing advanced functional hydrogels and the state-of-art applications of hydrogel-based flexible electronics in various fields are reviewed. More importantly, the correlation between properties of the hydrogel and device performance is discussed here, to have better understanding of the development of flexible electronics by using environmentally responsive hydrogels. Last, perspectives on the current challenges and future directions in the development of hydrogel-based multifunctional flexible electronics are provided.

Facile Fabrication of Lignin-Cellulose Green Nanogels.

There has been increasing exploration of the development and production of biodegradable polymers in response to issues with petrol-based polymers and their impact on the environment. Here we report a new approach to synthesize a natural nanogel from lignin and nanocellulose. First, lignin nanobeads were synthesized by a solvent-shifting method, which showed a spherical shape with a diameter of 159.7 nm. Then the lignin nanobeads were incorporated into a nanocellulose network to form the lignin/cellulose nanogels. The nanocellulose fibrils (CNF-C) nanogels reveal a higher storage modulus than the nanocellulose crystal (CNC-C) ones due to the denser network with self-entanglement of longer cellulose chains. The presence of lignin nanobeads in the nanogels helped to increase the viscoelasticity of the nanogels. This work highlights that the new kinds of green nanogels could be potentially utilized in a variety of biomedical applications such as drug delivery and wound dressing.

PLA-lignin nanofibers as antioxidant biomaterials for cartilage regeneration and osteoarthritis treatment.

BACKGROUND: Osteoarthritis (OA) is common musculoskeletal disorders associated with overgeneration of free radicals, and it causes joint pain, inflammation, and cartilage degradation. Lignin as a natural antioxidant biopolymer has shown its great potential for biomedical applications. In this work, we developed a series of lignin-based nanofibers as antioxidative scaffolds for cartilage tissue engineering. RESULTS: The nanofibers were engineered by grafting poly(lactic acid) (PLA) into lignin via ring-opening polymerization and followed by electrospinning. Varying the lignin content in the system was able to adjust the physiochemical properties of the resulting nanofibers, including fiber diameters, mechanical and viscoelastic properties, and antioxidant activity. In vitro study demonstrated that the PLA-lignin nanofibers could protect bone marrow-derived mesenchymal stem/stromal cells (BMSCs) from oxidative stress and promote the chondrogenic differentiation. Moreover, the animal study showed that the lignin nanofibers could promote cartilage regeneration and repair cartilage defects within 6 weeks of implantation. CONCLUSION: Our study indicated that lignin-based nanofibers could serve as an antioxidant tissue engineering scaffold and facilitate the cartilage regrowth for OA treatment.

How far is Lignin from being a biomedical material?

Lignin is a versatile biomass that possesses many different desirable properties such as antioxidant, antibacterial, anti-UV, and good biocompatibility. Natural lignin can be processed through several chemical processes. The processed lignin can be modified into functionalized lignin through chemical modifications to develop and enhance biomaterials. Thus, lignin is one of the prime candidate for various biomaterial applications such as drug and gene delivery, biosensors, bioimaging, 3D printing, tissue engineering, and dietary supplement additive. This review presents the potential of developing and utilizing lignin in the outlook of new and sustainable biomaterials. Thereafter, we also discuss on the challenges and outlook of utilizing lignin as a biomaterial.

Highly Efficient Supramolecular Aggregation-Induced Emission-Active Pseudorotaxane Luminogen for Functional Bioimaging.

The direct tracking of cells using fluorescent dyes is a constant challenge in cell therapy due to aggregation-induced quenching (ACQ) effect and biocompatibility issues. Here, we demonstrate the development of a biocompatible and highly efficient aggregation-induced emission (AIE)-active pseudorotaxane luminogen based on tetraphenylethene conjugated poly(ethylene glycol) (TPE-PEG2) (guest) and α-cyclodextrin (α-CD) (host). It is capable of showing significant fluorescent emission enhancement at the 400-600 nm range when excited at 388 nm, without increasing the concentration of AIE compound. The fluorescent intensity of TPE-PEG2 solution was effectively enhanced by 4-12 times with gradual addition of 1-4 mM of α-CD. 2D NOSEY 1H NMR revealed clear correlation spots between the characteristic peaks of α-CD and PEG, indicating the interaction between protons of ethylene glycol and cyclodextrin, and the structures are mainly based on threaded α-CD. The host-guest complex exhibits boosted fluorescent emission because the PEG side chains are confined in "nano-cavities" (host), thus, applying additional restriction on intermolecular rotation of TPE segments. In vitro cell experiments demonstrated the potential of AIE-active pseudorotaxane polymer as a biocompatible bioimaging probe.

Long-Term Real-Time In Vivo Drug Release Monitoring with AIE Thermogelling Polymer.

A new drug concentration meter is developed. In vivo drug release can be monitored precisely via a self-indicating drug delivery system consisting of a new aggregation-induced emission thermoresponsive hydrogel. By taking the advantage of a self-indicating system, one can easily detect the depletion of drugs, and reinject to maintain a dosage in the optimal therapeutic window.

Advances in nanomaterials and their applications in point of care (POC) devices for the diagnosis of infectious diseases.

Nanotechnology has gained much attention over the last decades, as it offers unique opportunities for the advancement of the next generation of sensing tools. Point-of-care (POC) devices for the selective detection of biomolecules using engineered nanoparticles have become a main research thrust in the diagnostic field. This review presents an overview on how the POC-associated nanotechnology, currently applied for the identification of nucleic acids, proteins and antibodies, might be further exploited for the detection of infectious pathogens: although still premature, future integrations of nanoparticles with biological markers that target specific microorganisms will enable timely therapeutic intervention against life-threatening infectious diseases.