The utilization of marine-based collagen is growing fast due to its unique properties in comparison with mammalian-based collagen such as no risk of transmitting diseases, a lack of religious constraints, a cost-effective process, low molecular weight, biocompatibility, and its easy absorption by the human body. This article presents an overview of the recent studies from 2014 to 2020 conducted on collagen extraction from marine-based materials, in particular fish by-products. The fish collagen structure, extraction methods, characterization, and biomedical applications are presented. More specifically, acetic acid and deep eutectic solvent (DES) extraction methods for marine collagen isolation are described and compared. In addition, the effect of the extraction parameters (temperature, acid concentration, extraction time, solid-to-liquid ratio) on the yield of collagen is investigated. Moreover, biomaterials engineering and therapeutic applications of marine collagen have been summarized.
Shortcomings related to the treatment of bone diseases and consequent tissue regeneration such as transplants have been addressed to some extent by tissue engineering and regenerative medicine. Tissue engineering has promoted structures that can simulate the extracellular matrix and are capable of guiding natural bone repair using signaling molecules to promote osteoinduction and angiogenesis essential in the formation of new bone tissues. Although recent studies on developing novel growth factor delivery systems for bone repair have attracted great attention, taking into account the complexity of the extracellular matrix, scaffolding and growth factors should not be explored independently. Consequently, systems that combine both concepts have great potential to promote the effectiveness of bone regeneration methods. In this review, recent developments in bone regeneration that simultaneously consider scaffolding and growth factors are covered in detail. The main emphasis in this overview is on delivery strategies that employ polymer-based scaffolds for spatiotemporal-controlled delivery of both single and multiple growth factors in bone-regeneration approaches. From clinical applications to creating alternative structural materials, bone tissue engineering has been advancing constantly, and it is relevant to regularly update related topics.
Fabrication
of reinforced scaffolds for bone regeneration remains
a significant challenge. The weak mechanical properties of the chitosan
(CS)-based composite scaffold hindered its further application in
clinic. Here, to obtain hydroxyethyl CS (HECS), some hydrogen bonds
of CS were replaced by hydroxyethyl groups. Then, HECS-reinforced
polyvinyl alcohol (PVA)/biphasic calcium phosphate (BCP) nanoparticle
hydrogel was fabricated via cycled freeze-thawing followed by an in vitro biomineralization treatment using a cell culture
medium. The synthesized hydrogel had an interconnected porous structure
with a uniform pore distribution. Compared to the CS/PVA/BCP hydrogel,
the HECS/PVA/BCP hydrogels showed a thicker pore wall and had a compressive
strength of up to 5–7 MPa. The biomineralized hydrogel possessed
a better compressive strength and cytocompatibility compared to the
untreated hydrogel, confirmed by CCK-8 analysis and fluorescence images.
The modification of CS with hydroxyethyl groups and in vitro biomineralization were sufficient to improve the mechanical properties
of the scaffold, and the HECS-reinforced PVA/BCP hydrogel was promising
for bone tissue engineering applications.
An interpenetrating network (IPN) strategy has been widely facilitated to construct strong and tough hydrogels, but most of the efforts have been focused on organic/organic networks. Herein, aqueous dispersible 2,2'-(ethylenedioxy)-diethanethiol (EDDET) cross-linked graphene oxide (E-cGO) skeleton was in situ incorporated into a PVA matrix, resulting in novel inorganic/organic IPN hydrogels with super mechanical and chondrocyte cell-adhesion properties. The unique interpenetrating structure and hydrogen bonding were demonstrated to play critical roles in enhancing the compressive property of the IPN hydrogels, in comparison to the GO and thermally reduced graphene oxide (T-rGO) filled hydrogels. It is critical that the E-cGO/PVA hydrogels have been demonstrated as being biocompatible, which make the E-cGO/PVA hydrogels promising candidate biomaterials for load-bearing biotissue substitution.
A versatile ion release mediated by GDL is demonstrated to achieve a controlled homogeneous crosslinking of alginate chains, which is critical for the synthesis of highly stretchable and notch-insensitive hybrid hydrogels with controlled properties.
Highlights• The need for the modification of alginate properties was established • Click chemistry reactions were discussed • Functionality of using click chemistry for alginate-based materials was explored
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