Mussel-Inspired Anisotropic Nanocellulose and Silver Nanoparticle Composite with Improved Mechanical Properties, Electrical Conductivity and Antibacterial Activity

Materials for wearable devices, tissue engineering and bio-sensing applications require both antibacterial activity to prevent bacterial infection and biofilm formation, and electrical conductivity to electric signals inside and outside of the human body. Recently, cellulose nanofibers have been utilized for various applications but cellulose itself has neither antibacterial activity nor conductivity. Here, an antibacterial and electrically conductive composite was formed by generating catechol mediated silver nanoparticles (AgNPs) on the surface of cellulose nanofibers. The chemically immobilized catechol moiety on the nanofibrous cellulose network reduced Ag+ to form AgNPs on the cellulose nanofiber. The AgNPs cellulose composite showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria. In addition, the catechol conjugation and the addition of AgNP induced anisotropic self-alignment of the cellulose nanofibers which enhances electrical and mechanical properties of the composite. Therefore, the composite containing AgNPs and anisotropic aligned the cellulose nanofiber may be useful for biomedical applications.open11128sciescopu

해양 무척추동물 모사 골형성연구

DoctorBone regeneration is a well-integrated physiological process of bone formation which can notably be seen during fracture healing. Generally, bone regeneration happened slowly in continuous bone remodeling process throughout adult life. However, there are special conditions in which bone regeneration is required in large quantity and in a short time period, for example in a case of skeletal reconstruction of large bone defects which usually created by trauma, infection, tumor resection, or other abnormalities. Other cases are in which the regenerative process is needed to overcome avascular necrosis, atrophic non-unions, and osteoporosis. Currently, there are a plethora of different strategies to augment the impaired or 'insufficient' bone regeneration process. The clinical 'gold standard' methods commonly used now are autologous bone graft, allograft implantation, and use of growth factors, osteoconductive scaffolds, osteoprogenitor cells and distraction osteogenesis. However, these methods usually are limited in their efficacy, cost-effectiveness, and biocompatibility issue. Therefore, in last decades there have been many attempts to accelerate the overall regeneration process and address the aforementioned symptoms. Marine biomaterial is one of the newly emerging bone regeneration research with broad biomedical applications potential. This is thanks to the fact that marine-originated materials offer many similarities with human body condition. For examples, both systems are naturally saline, encounter variation of control over fluid flow, fouling by flowing via macromolecules, and having degradation of organics via cellular-level activities. Therefore, understanding physics properties and chemistry of marine biomaterials has provided scientists useful insights for designing biomaterials for biomedical application. Exoskeletons of marine invertebrates such as squid beak and crab shell have attracted the attentions of scientists and engineers since they are lightweight and have mechanical properties similar to human bone in wet conditions. These exoskeletons are mainly composed of chitin/chitosan and polyphenolic crosslinks which can be utilized to regenerate part of human's skeletal structure. In chapter II, we fabricated HAp-chitosan composites and used dopamine to crosslink the organic chitosan phase to the inorganic HAp phase. Dopamine crosslinking on the HAp-chitosan composite enhanced the mechanical properties of the composite in wet conditions. In addition, in the presence of dopamine, HAp particles grew anisotropically into a needle shape with high AR. In chapter III, inspired by tunicate's self-healing ability, we successfully developed a facile, patient-friendly, aesthetically acceptable and instant dentin hypersensitivity treatment by using catechol derivatives; Gallic acid and Tannic acid with metal chelates. In the first 4 mins, the GA/metal coating showed the best result that blocked almost 60% of tooth slices. After 7 days of saliva-mediated incubation, this densely packed HAp blocked nearly 87%. These products offer tantalizing pre-made options that are versatile, adaptable and have potential functions for current tissue engineers seeking fresh solutions to bone and tissue regenerating issues

Review of the corrosion behaviour in tannic-acid coated magnesium implants

Magnesium is a bio-degradable material used for bone implants because of its similar mechanical properties to bones. However, magnesium has a high corrosion rate, resulting in an implant’s degradation before the bone is fully healed. Thus, researches are conducted to study ways to improve the corrosion resistance of magnesium. Coating is one of the methods to hinder the corrosion rate of magnesium. There are two types of coatings: organic and inorganic. Organic coatings are preferable due to their non-toxicity and good biocompatibility. Tannic acid (TA) is an organic coating with a strong bond with magnesium due to its many hydroxyl groups. Besides bonding with the substrate material, tannic acid can also bind with other compounds or elements to improve the performance of the coating layer. This review evaluated several types of TA-based coatings on magnesium alloys used in orthopaedic implants and the fabrication processes affecting the structural integrity of the coating. The strategies for using TA-compound combination for corrosion mitigation with ease of fabrication process were also highlighted. This review is expected to provide some insight on the challenges and future directions of TA-based magnesium coatings for orthopaedic applications

Role of Dopamine Chemistry in the Formation of Mechanically Strong Mandibles of Grasshoppers

Role of Dopamine Chemistry in the Formation of Mechanically Strong Mandibles of Grasshopper

Marine hydroid perisarc: a chitin- and melanin-reinforced composite with DOPA-iron(III) complexes.

Many marine invertebrates utilize biomacromolecules as building blocks to form their load-bearing tissues. These polymeric tissues are appealing for their unusual physical and mechanical properties, including high hardness and stiffness, toughness and low density. Here, a marine hydroid perisarc of Aglaophenia latirostris was investigated to understand how nature designs a stiff, tough and lightweight sheathing structure. Chitin, protein and a melanin-like pigment, were found to represent 10, 17 and 60 wt.% of the perisarc, respectively. Interestingly, similar to the adhesive and coating of marine mussel byssus, a DOPA (3,4-dihydroxyphenylalanine) containing protein and iron were detected in the perisarc. Resonance Raman microprobe analysis of perisarc indicates the presence of catechol-iron(III) complexes in situ, but it remains to be determined whether the DOPA-iron(III) interaction plays a cohesive role in holding the protein, chitin and melanin networks together

Marine hydroid perisarc: A chitin- and melanin-reinforced composite with DOPA–iron(III) complexes

Many marine invertebrates utilize biomacromolecules as building blocks to form their load-bearing tissues. These polymeric tissues are appealing for their unusual physical and mechanical properties, including high hardness and stiffness, toughness and low density. Here, a marine hydroid perisarc of Aglaophenia latirostris was investigated to understand how nature designs a stiff, tough and lightweight sheathing structure. Chitin, protein and a melanin-like pigment, were found to represent 10, 17 and 60 wt.% of the perisarc, respectively. Interestingly, similar to the adhesive and coating of marine mussel byssus, a DOPA (3,4-dihydroxyphenylalanine) containing protein and iron were detected in the perisarc. Resonance Raman microprobe analysis of perisarc indicates the presence of catechol-iron(III) complexes in situ, but it remains to be determined whether the DOPA-iron(III) interaction plays a cohesive role in holding the protein, chitin and melanin networks together. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.X111615sciescopu

Biomimetic Janus chitin nanofiber membrane for potential guided bone regeneration application

Biopolymer-based membranes are at the forefront of the guided bone regeneration (GBR) in orthopaedics and dentistry, which prevent fast-growing soft tissue migration to the defected alveolar ridge or implants and allow the bone regeneration. In this study, we fabricated a novel Janus -two-faced, GBR membrane composed of a chitin nanofiber face for bone regeneration and a cell membrane mimetic antifouling 2-Methacryloyloxyethyl phosphorylcholine (MPC) polymeric face for suppressing the migration of the soft tissue. In vitro cell study showed a higher cell proliferation rate of osteoblast cells on the chitin nanofiber surface and a lower proliferation rate of fibroblasts cells on the antifouling MPC side. An increased of Alkaline Phosphatase (ALP) rate was observed in the chitin nanofiber face, indicating the ability to maintain proliferation and differentiation of osteogenic cells. These results suggest the biomimetic Janus chitin membrane may have the potential to develop as an advance GBR membrane.11Nsciescopu