Hydroxyapatite (HA) and related materials have been frequently studied as ceramic-based bone graft materials due to their outstanding biocompatibility and osteoconduction. Since the bones are the load supporting parts of a vertebrate, they must have good fracture toughness (KIC) to avoid fracture at high loading during limb movements. However, the main shortcomings of HA are the poor fracture toughness and brittleness. The mechanical properties of HA need to be improved for orthopedic applications, therefore it is often fabricated with other materials into a composite. This article focuses on the effect of carbon nanostructures (CNSs) especially graphene nanoplatelets (GNPs) on the mechanical, physicochemical properties and in-vitro bio-functional performances of HA. We provide an overview on the preparation and characterization of the HA–GNPs composites. To conclude, the challenges in the fabrication of multi-substituted HA–GNPs composites and future outlooks in the biomedical domain are discussed.

Overview of Hydroxyapatite–Graphene Nanoplatelets Composite as Bone Graft Substitute: Mechanical Behavior and In-vitro Biofunctionality

We report on the design, development, characterization, and a preliminary cellular evaluation of a novel solid material. This material is composed of low-molecular-weight hyaluronic acid (LMWHA) and polyarginine (PArg), which generate aqueous ionic nanocomplexes (INC) that are then freeze-dried to create the final product. Different ratios of LMWHA/PArg were selected to elaborate INC, the size and zeta potential of which ranged from 100 to 200 nm and +25 to −43 mV, respectively. Turbidimetry and nanoparticle concentration analyses demonstrated the high capacity of the INC to interact with increasing concentrations of LMWHA, improving the yield of production of the nanostructures. Interestingly, once the selected formulations of INC were freeze-dried, only those comprising a larger excess of LMWHA could form reproducible sponge formulations, as seen with the naked eye. This optical behavior was consistent with the scanning transmission electron microscopy (STEM) images, which showed a tendency of the particles to agglomerate when an excess of LMWHA was present. Mechanical characterization evidenced low stiffness in the materials, attributed to the low density and high porosity. A preliminary cellular evaluation in a fibroblast cell line (RMF-EG) evidenced the concentration range where swollen formulations did not affect cell proliferation (93–464 µM) at 24, 48, or 72 h. Considering that the reproducible sponge formulations were elaborated following inexpensive and non-contaminant methods and comprised bioactive components, we postulate them with potential for biomedical purposes. Additionally, this systematic study provides important information to design reproducible porous solid materials using ionic nanocomplexes.

https://www.mdpi.com/2079-4991/9/7/944/pdf

Ionic Nanocomplexes of Hyaluronic Acid and Polyarginine to Form Solid Materials: A Green Methodology to Obtain Sponges with Biomedical Potential.

In a general wound healing process, foreign bodies and tissue detritus have to be broken down and then a new tissue is produced. However, the new tissue formation sometimes fails to proceed under the impaired conditions such as burn injury and intractable skin ulcer. A major obstruction to wound healing is infection. Another obstruction to wound healing is deficiency of growth factors. The endogenous levels of growth factors are reduced in some chronic wounds. To improve these wound conditions, researchers have been trying to create several types of artificial skins. The tissue-engineered products include three prime constituents, i.e., cells, growth factors, and materials. In this review, the practical design of tissue-engineered products for skin regenerative medicine is introduced. The first design makes it possible to release silver sulfadiazine (AgSD) from a wound dressing. The second design makes it possible to release Epidermal Growth Factor (EGF) from a wound dressing or a skin care product composed of hyaluronic acid spongy sheet containing bioactive ingredients. The third design makes it possible to release several types of growth factors from allogeneic fibroblasts within cultured dermal substitute. This tissue-engineered product is prepared by seeding allogeneic fibroblasts into a collagen and hyaluronic acid spongy sheet. Although allogeneic cells are rejected gradually in immune system, they are able to release some types of growth factors, thereby regenerating a damaged tissue. The clinical study demonstrates that these tissue-engineered products are promising for the treatment of burn injury and intractable skin ulcer.

/pdf/tissue-engineered-products-for-skin-regenerative-medicine-2trma35xze.pdf

Tissue-Engineered Products for Skin Regenerative Medicine

This study aimed to investigate the potential of a skin care product composed of hyaluronic acid (HA) and collagen (Col) sponge containing epidermal growth factor (EGF), vitamin C derivative (VC), glucosylceramide (GC), poly(γ-glutamic acid) (PGA), and argentine (Arg). High-molecular weight HA aqueous solution, hydrolyzed low-molecular weight HA aqueous solution, and heat- denatured Col aqueous solution were mixed, into which each aqueous solution containing EGF, VC, GC, PGA, or Arg were added, followed by freeze-drying to obtain a spongy EGF-incorporating skin care product (EGF-skin care product). In order to evaluate the first efficacy of EGF, fibroblast proliferation was assessed after 6 days of cultivation in the conditioned medium prepared by dissolving EGF-skin care product in a conventional culture medium. The fibroblast densities increased more effectively in conditioned medium with EGF than in control medium without EGF. In order to evaluate the second efficacy of EGF, the amount of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) produced by fibroblasts were assessed in a wound surface model. A fibroblast-incorporating Col gel sheet (cultured dermal substitute: CDS) was elevated to the air- medium interface, onto which a spongy sheet of EGF-skin care product was placed and cultured for 7 days. The condition covered with or without EGF-skin care product is divided into (+) EGF or (-) EGF, respectively. Fibroblasts in the CDS released 3.7 times more VEGF and 25 times more HGF in (+) EGF compared with (-) EGF. In another experiment, an aqueous solution of EGF-skin care product was added onto CDS and cultured for 7 days. Aqueous solutions were prepared and stored at 4°C or 37°C for a different period of 1 day, 2 weeks, and 4 weeks, respectively. Fibroblasts in CDS under different condition released similar amount of VEGF and HGF. This result indicated that the efficacy of EGF was maintained even after preservation at 37°C for 4 weeks. These findings suggest that EGF-skin care product can be used on damaged skin surface by placing its spongy sheet or its solution.

/pdf/evaluation-of-epidermal-growth-factor-incorporating-skin-1kncqzh5a2.pdf

Evaluation of Epidermal Growth Factor-Incorporating Skin Care Product in Culture Experiment Using Human Fibroblasts

The research progress in in vivo expression, degradative enzyme, serum level detection, immunogenicity and application in pharmaceutical and cosmetic field of poly-gamma-glutamate (poly-gamma-glutamate, PGA) are reviewed in this paper, to provide reference for further research and development.

Research Progress in Poly-gamma-glutamate

Eight types of spongy sheet were prepared by freeze-drying aqueous solutions of hyaluronic acid (HA) and poly(γ-glutamic acid) (PGA) with or without bioactive components including vitamin C derivative (VC), glucosylceramide (GC), and epidermal growth factor (EGF). Spongy sheets were categorized into the following groups: Group I (HA/PGA), Group II (HA/PGA + VC), Group III (HA/PGA + GC), Group IV (HA/PGA + VC, GC), Group V (HA/PGA + EGF), Group VI (HA/PGA + VC, EGF), Group VII (HA/PGA + GC, EGF), and Group VIII (HA/PGA + VC, GC, EGF). In the first experiment, we examined fibroblast proliferation in conditioned medium that had been prepared by immersing each spongy sheet in a conventional culture medium. EGF-incorporating spongy sheets (Groups V-VIII) enhanced fibroblast proliferation more than EGF-free spongy sheets (Groups I-IV). In the second experiment, cytokine production by fibroblasts was evaluated using a wound surface model. This involved elevation of fibroblasts-incorporating collagen gel sheets to the air-liquid interface, on which a spongy sheet (Groups I, IV, V and VIII) was placed and cultured for 1 week. EGF-incorporating spongy sheets (Groups V and VIII) enhanced the production of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) by fibroblasts more than EGF-free spongy sheets (Groups I and IV). The effect of these four types of spongy sheet on wounds was investigated in animal experiments. Chemical peel was performed by contacting 50% trichloroacetic acid (TCA) on the dorsal region of mice, after which a spongy sheet was placed, and the wound condition was then observed in a two-week period. Angiogenesis was facilitated to a greater degree in Group VIII compared with Groups I, IV and V. This finding indicates that Group VIII spongy sheet is a promising aid for skin recovery after chemical peel.

https://file.scirp.org/pdf/OJRM_2014090313293972.pdf

Development of a Freeze-Dried Skin Care Product Composed of Hyaluronic Acid and Poly(γ-Glutamic Acid) Containing Bioactive Components for Application after Chemical Peels

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Development of a Freeze-Dried Skin Care Product Composed of Hyaluronic Acid and Poly(γ-Glutamic Acid) Containing Bioactive Components for Application after Chemical Peels