China
Africa
Explore chapters and articles related to this topic
Absorbable Soft Tissue Fillers: Core Characteristics
Published in Ali Pirayesh, Dario Bertossi, Izolda Heydenrych, Aesthetic Facial Anatomy Essentials for Injections, 2020
Ali Pirayesh, Colin M. Morrison, Berend van der Lei, Ash Mosahebi
The process of crosslinking (Figure F.1) adds a molecule to link the polymer chains to each other, thus modifying their physical properties to make them longer-lasting and less likely to be degraded. The most commonly used crosslinker is 1,4-butanediol diglycidyl ether (BDDE); BDDE has a significantly lower toxicity than other crosslinking agents (e.g., divinyl sulfone or formaldehyde) and is biodegradable [9–11].
Biological reactions to reconstructive materials
Published in Steven J. Kronowitz, John R. Benson, Maurizio B. Nava, Oncoplastic and Reconstructive Management of the Breast, 2020
Steven J. Kronowitz, John R. Benson, Maurizio B. Nava
Collagen cross-linking in ADMs has been shown to be another determinant of biologic response. The purpose of cross-linking is to mechanically strengthen the ADM and prevent its degradation.7,28 Intentional cross-linking occurs through the use of chemical agents such as gluteraldhyde, whereas unintentional cross-linking of collagen can result from processes such as gamma irradiation used to sterilize the ADM.7 Cross-linked porcine ADM has been shown to undergo less cellular infiltration and neovascularization when compared to non-cross-linked porcine ADM.29 However, newer cross-linking technologies may offer benefits of improved strength paired with improved biointegration.30
Injectable Scaffolds for Bone Tissue Repair and Augmentation
Published in Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon, Tissue Engineering Strategies for Organ Regeneration, 2020
Subrata Bandhu Ghosh, Kapender Phogat, Sanchita Bandyopadhyay-Ghosh
There is a growing trend to develop the injectable hydrogel scaffolds using physical cross-linking techniques (Huh et al. 2012). This is because of the fact that chemical cross-linking involves use of cross-linkers which are often toxic in nature and the unreacted cross-linkers if present, have to be removed/extracted, before application inside the body. Besides, the chemical cross-linkers can adversely affect the immobilized substances (e.g. proteins, cells) within the hydrogel. Physical cross-linking can surpass the above limitations; however, the polymeric network, obtained primarily from inter-chain secondary bonding usually results into limited mechanical strength and stability (Hoffman 2012, Hou et al. 2004, Huh et al. 2012). Physical cross-linking may be initiated by different techniques. Examples of such techniques include ionic interactions, crystallization, use of amphiphilic block and graft copolymers, hydrogen bonding, protein interactions, in situ precipitation, etc (Jeong et al. 2016). The physically cross-linked gels have been used as injectable delivery vehicles for bone scaffold applications (Paige et al. 1995). Table 7.2 lists some of the useful techniques for synthesis of physical cross-linked hydrogels.
PDMS networks meet barnacles: a complex and often toxic relationship
Published in Biofouling, 2022
Daniel Rittschof, Beatriz Orihuela, Jan Genzer, Kirill Efimenko
In the initial studies, the range of TDSS toxicity on the nauplii by changing the concentration of TDSS molecules was tested by mixing it with base polymer without employing the crosslinking reaction, thus remaining free in the silicone mixture. In PDMSe coatings, a crosslinker is one of the components that can be potentially extracted into the AFSW even from the fully crosslinked system. Our approach directly assesses crosslinker toxicity without employing the network structure. All studies were performed using v-PDMS with Mw = 49.5 kDa using the protocol outlined in the material section. While the acute naupliar toxicity of seawater equilibrated with v-PDMS for 24 h (1 ml of PDMS in 10 ml of AFSW) was minimal, it was still toxic enough to barnacle nauplii with full-strength leachate killing 35% of the population compared to control mortality of 6% in AFSW. Leachates from a dilution series of crosslinkers were mixed in v-PDMS and then leached with seawater. They showed a concentration-dependent response with toxicity increasing from about 40% mortality at leachate collected from 3.0 mg ml−1 (TDSS in PDMS) to leachate at 19.0 mg ml−1 (TDSS/PDMS), at which 100% of nauplii were killed (cf. Figure 1). For reference, the recipe used in the formulation of the siloxane network uses 11.3 mg of TDSS, and 92 µg of Pt (II) catalyst in 1.0 ml of polymer of v-PDMS with a molecular weight of 49.5 kDa. It is important to note that the reference system undergoes the crosslinking reaction, which significantly reduces the leachable unbound components from the network.
The measurement of wound tensile strength and the effect of PRP on wound tensile force: an experimental investigation on rabbits
Published in Journal of Plastic Surgery and Hand Surgery, 2022
Ali Gökkaya, Metin Görgü, Jehat Kızılkan, Ertuğrul Karanfil, Ali Doğan
Platelets start the inflammation phase of wound healing and manage it. Inflammatory, proliferative and remodeling are stages of wound healing. After activation by tissue damage, platelets initiate hemostasis and wound healing. Activated platelets promote wound healing by releasing biologically active proteins and growth factors (such as platelet-derived growth factor, transforming growth factor-b, fibroblast growth factor, epidermal growth factor, keratinocyte growth factor, and vascular endothelium growth factors) resulting in connective tissue healing, epithelial development, angiogenesis, and deposition of the collagen matrix. During the wound healing process, the tensile strength of the wound increases progressively. This increase is greater in the first week; later on, it is directly related to the increase in collagen production, and it stabilizes when collagen production and destruction are in balance. Weak crosslinks change to strong crosslinks and tensile strength increases progressively until the tensile force reaches an optimum strength. The stages of wound healing directly affect the tensile strength of the wound.
Crosslinking hyaluronic acid soft-tissue fillers: current status and perspectives from an industrial point of view
Published in Expert Review of Medical Devices, 2021
Jimmy Faivre, Amos I. Pigweh, Julien Iehl, Pauline Maffert, Peter Goekjian, François Bourdon
Each of these crosslinkers raise interesting advantages and challenges from the process point of view, yet in all cases, the principal issue to be considered in medical practice remains the metabolic fate of the crosslinker during resorption. The three key rationales for developing new crosslinkers for native HA are thus: (1) improving the physical properties of the hydrogel filler; (2) improving process issues, including reaction conditions, crosslinker solubility, and purification conditions, the latter being a necessarily time-consuming and costly step of the process; (3) improving the metabolic fate of the crosslinker and crosslinking residues. The perfect crosslinker would add useful properties to the gel, be perfectly water soluble, react under mild conditions, be easy to extract from the gel, and be metabolized though well-known and nontoxic pathways.