This article reports the first hydrogel with the strength and modulus of cartilage in both tension and compression, and the first to exhibit cartilage‐equivalent tensile fatigue strength at 100 000 cycles. These properties are achieved by infiltrating a bacterial cellulose (BC) nanofiber network with a poly(vinyl alcohol) (PVA)–poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid sodium salt) (PAMPS) double network hydrogel. The BC provides tensile strength in a manner analogous to collagen in cartilage, while the PAMPS provides a fixed negative charge and osmotic restoring force similar to the role of aggrecan in cartilage. The hydrogel has the same aggregate modulus and permeability as cartilage, resulting in the same time‐dependent deformation under confined compression. The hydrogel is not cytotoxic, has a coefficient of friction 45% lower than cartilage, and is 4.4 times more wear‐resistant than a PVA hydrogel. The properties of this hydrogel make it an excellent candidate material for replacement of damaged cartilage.
Acne vulgaris is a common inflammatory skin disease associated with a colonization of Propionibacterium acnes (P. acnes), which can cause both physiological and psychological impact to the patients. Although antibiotic cream is commonly used to treat acne, limited transport of drug to the lesions within the pilosebaceous unit leads to poor bactericidal effect. Here, the authors described a new method of drug administration using a reactive oxygen species (ROS)‐responsive microneedle (MN) patch for anti‐acne therapy. Compared to the commonly used anti‐acne cream, enhanced efficacy toward dermis lesions can be achieved through the skin penetration by MNs. A controlled and sustained drug release in response to the over‐generated ROS within acne is also important for improving the antibacterial effect and reducing the side effects. In addition, the patch base, formed by hyaluronic acid (HA) and diatomaceous earth (DE) with high physical adsorption capability, is beneficial for accelerating healing of skin via the absorption of pus and dead cell debris. In vivo studies in a P. acnes‐induced mouse model demonstrated this bioresponsive patch with adsorption capability could efficiently reduce the skin swelling and inhibit the bacterial growth.
Key hurdles for replacing damaged cartilage with an equivalent synthetic construct are the development of a hydrogel with a strength that exceeds that of cartilage and fixation of this hydrogel onto the surface of an articulating joint. This article describes the first hydrogel with a tensile and compressive strength (51 and 98 MPa) that exceeds those of cartilage (40 and 59 MPa), and the first attachment of a hydrogel to a metal backing with a shear strength (2.0 MPa) that exceeds that of cartilage on bone (1.2 MPa). The hydrogel strength is achieved through reinforcement of crystallized polyvinyl alcohol with bacterial cellulose. The high attachment strength is achieved by securing freeze-dried bacterial cellulose to a metal backing with an adhesive and a shape memory alloy clamp prior to infiltration and crystallization of the polyvinyl alcohol. The bacterial cellulose-reinforced polyvinyl alcohol is three times more wear resistant than cartilage over one million cycles and exhibits the same coefficient of friction. These advances in hydrogel strength and attachment enable the creation of a hydrogel-based implant for durable resurfacing of damaged articulating joints.
A multimodal cancer therapeutic nanoplatform is reported. It demonstrates a promising approach to synergistically regulating the tumor microenvironment. The combination of intracellular reactive oxygen species (ROS) generated by irradiation of photosensitizer and endoplasmic reticulum (ER) stress induced by 2‐deoxy‐glucose (2‐DG) has a profound effect on necrotic or apoptotic cell death. Especially, targeting metabolic pathway by 2‐DG is a promising strategy to promote the effect of photodynamic therapy and chemotherapy. The nanoplatform can readily release its cargoes inside cancer cells and combines the advantages of ROS‐sensitive releasing chemotherapeutic drugs, upregulating apoptosis pathways under ER stress, light‐induced generation of cytotoxic ROS, achieving tumor accumulation, and in vivo fluorescence imaging capability. This work highlights the importance of considering multiple intracellular stresses as design parameters for nanoscale functional materials in cell biology, immune response, as well as medical treatments of cancer, Alzheimer's disease, etc.
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