In vitro study of transportation of porphyrin immobilized graphene oxide through blood brain barrier.

Blood brain barrier (BBB), a barrier formed by endothelial cells, separates the brain from the circulatory system and protects the stability of central neural system normally, however, it also results in low permeability of vast majority of drugs for brain disease therapy. In this work, the cytotoxicity, uptake and transportation of 2D graphene nanosheet through BBB were investigated in in vitro models of BBB constructed by human brain microvascular endothelia cells (hBMECs). Permeability of two types of graphene nanosheet, including graphene oxide (GO) and porphyrin conjugated graphene oxide (PGO) through BBB were studied. With hydrophobic chemicals conjugation on its surface, permeability of PGO was greatly improved compared to GO. Furthermore, transportation behavior of assorted sizes of PGO obtained by differential velocity centrifugation through BBB was also explored, revealing that PGO with larger size has higher permeability than smaller-size PGO. The significant improved permeability of 2D graphene nanosheet through BBB compared to traditional drugs provides promising applications in drug delivery and disease therapy for brain disease in the near future.

Ultrasensitive Wearable Strain Sensors of 3D Printing Tough and Conductive Hydrogels.

In this study, tough and conductive hydrogels were printed by 3D printing method. The combination of thermo-responsive agar and ionic-responsive alginate can highly improve the shape fidelity. With addition of agar, ink viscosity was enhanced, further improving its rheological characteristics for a precise printing. After printing, the printed construct was cured via free radical polymerization, and alginate was crosslinked by calcium ions. Most importantly, with calcium crosslinking of alginate, mechanical properties of 3D printed hydrogels are greatly improved. Furthermore, these 3D printed hydrogels can serve as ionic conductors, because hydrogels contain large amounts of water that dissolve excess calcium ions. A wearable resistive strain sensor that can quickly and precisely detect human motions like finger bending was fabricated by a 3D printed hydrogel film. These results demonstrate that the conductive, transparent, and stretchable hydrogels are promising candidates as soft wearable electronics for healthcare, robotics and entertainment.

Thermal-Recoverable Tough Hydrogels Enhanced by Porphyrin Decorated Graphene Oxide.

Artificial tissue materials usually suffer properties and structure loss over time. As a usual strategy, a new substitution is required to replace the worn one to maintain the functions. Although several approaches have been developed to restore the mechanical properties of hydrogels, they require direct heating or touching, which cannot be processed within the body. In this manuscript, a photothermal method was developed to restore the mechanical properties of the tough hydrogels by using near infrared (NIR) laser irradiation. By adding the porphyrin decorated graphene oxide (PGO) as the nanoreinforcer and photothermal agent into carrageenan/polyacrylamide double network hydrogels (PDN), the compressive strength of the PDN was greatly improved by 104%. Under a short time of NIR laser irradiation, the PGO effectively converts light energy to thermal energy to heat the PDN hydrogels. The damaged carrageenan network was rebuilt, and a 90% compressive strength recovery was achieved. The PGO not only significantly improves the mechanical performance of PDN, but also restores the compressive property of PDN via a photothermal method. These tough hydrogels with superior photothermal recovery may work as promising substitutes for load-bearing tissues.

Porphyrin Immobilized Nanographene Oxide for Enhanced and Targeted Photothermal Therapy of Brain Cancer.

Brain cancer is a fatal disease that is difficult to treat because of poor targeting and low permeability of chemotherapeutic drugs through the blood brain barrier. In a comparison to current treatments, such as surgery followed by chemotherapy and/or radiotherapy, photothermal therapy is a remarkable noninvasive therapy developed in recent years. In this work, porphyrin immobilized nanographene oxide (PNG) was synthesized and bioconjugated with a peptide to achieve enhanced and targeted photothermal therapy for brain cancer. PNG was dispersed into the agar based artificial tissue model and demonstrated a photo-to-thermal conversion efficiency of 19.93% at a PNG concentration of only 0.5 wt %, with a heating rate of 0.6 °C/s at the beginning of irradiation. In comparison, 0.5 wt % graphene oxide (GO) indicated a photo-to-thermal conversion efficiency of 12.20% and a heating rate of 0.3 °C/s. To actively target brain tumor cells without harming healthy cells and tissues surrounding the laser path, a tripeptide l-arginyl-glycyl-l-aspartic (RGD) was further grafted to PNG. The photothermal therapy effects of PNG-RGD completely eliminated the tumor in vivo, indicating its excellent therapeutic effect for the treatment of brain cancer.

Tough and fully recoverable hydrogels.

In natural cartilage, collagen fibers form the extracellular matrix, while aggrecan entangles with these fibers and provides cartilage with its osmotic properties, which are critical to resist cyclic compressive loads. In this paper, a hydrogel was fabricated via the entanglement of a bio-inspired nanostructure (chondroitin sulfate-coated vinyl silica nanoparticles, CS-SNP) within an agar/poly(acrylamide) double network hydrogel. The highly charged chondroitin sulfate groups provide additional compression resistance within the macromolecular chains, while the solid silica cores anchor these entanglements. The presence of the CS-SNP not only improved the compressive modulus, compressive strength, fracture toughness, and fatigue resistance of this hydrogel, but also ensured the full recovery of all these properties after thermal heating. This tough, fully recoverable, and robust hydrogel is a promising material for applications with strong mechanical requirements.