China
Africa
Explore chapters and articles related to this topic
Hydrogels with Ubiquitous Roles in Biomedicine and Tissue Regeneration
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
Priyanka, Pooja A Chawla, Aakriti, Viney Chawla, Durgesh Nandini Chauhan, Bharti Sapra
Natural polymers (e.g. collagen and alginate), acellular tissue matrices (e.g. decellularised tissues or organs), and synthetic biodegradable polymers (e.g. polyglycolic acid (PGA), polylactic acid (PLA), poly (lactic-co-glycolic acid) and their copolymers are frequently used for TE application (Kim et al., 2000; Lee et al., 2018). Biomaterials can be classified on the basis of structure as well as function (Dolcimascolo et al., 2019) (Figure10.1 summarises this classification), e.g. whether biomaterials are applied directly in the tissue in the form of injectable (Gutowska et al., 2001) or non-injectable hydrogels; carriers or scaffolds and as surface modification, etc. (Baroli, 2007; Kretlow et al., 2007).
Vaccine Adjuvants in Immunotoxicology
Published in Mesut Karahan, Synthetic Peptide Vaccine Models, 2021
Nanoparticles are manufactured using albumin, collagen, starch, chitosan, and dextran out of natural polymers and polymethylmethacrylate, polyesters, polyanhydrides, and polyamides among synthetic polymers (Li et al. 2014). There are biodegradable or non-biodegradable polymers. Non-biodegradable polymers may cause unexpected effects by accumulation in the body. In the vaccine studies, the characteristics such as toxic effects of the polymer on the organism, antigen release speed capacity, stability status under storage conditions, and stability in the in vivo conditions should be taken into account in making a decision for an ideal polymer carrier system (Skwarczynski and Toth 2011, 2016). The comprehensive toxicity tests for several synthetic polymers such as polyesters, polylactic acid (PLA), polyglycolic acid, and their copolymers poly(lactic-co-glycolic acid) (PLGA) have been carried out and they are FDA-approved for use in humans (Li et al. 2014; Cordeiro and Alonso 2016). The most commonly used biodegradable polymers are PLA, PLGA, polyglutamic acid (PGA), polycaprolactone (PCL), and polyhydroxybutyrate. PLGA is the most frequently used polymer in the nanoparticle studies (Li et al. 2014). Skwarczynski and Toth (2011) have reported in their study that MUC-1 peptide vaccine assembled into PLGA nanoparticle carrier system accompanied with adjuvant MPLA created immune response by inducing T cells. However, it has been noted in the same article that need for use of adjuvant in the PLGA-based systems still continues (Skwarczynski and Toth 2011).
Animal Selections in Orthopaedic Research
Published in Yuehuei H. An, Richard J. Friedman, Animal Models in Orthopaedic Research, 2020
Yuehuei H. An, Richard J. Friedman
For example, in the development of a new bioabsorbable material, measurements of its mechanical strength and degradation rate in a saline environment must be tested. Its biocompatibility in cell culture must also be assessed (Figure 1). After these in vitro studies, the material cannot immediately be tested in humans because it may have undetected toxic effects in human tissues. In the past, some products containing polylactide acid (PLA) and polyglycolic acid (PGA) have caused tissue lysis in human subjects leading to aseptic abscesses. Will the new absorbable material cause a similar problem? This question has to be answered before clinical trials are undertaken. Therefore, an animal model (using lower level animals such as rats) can be used to test the biocompatibility and degradation rate of the material, in vivo. Tests such as these are normally accomplished by subcutaneous and intraosseous implantation. If the experiment does not reveal any significant toxic effects, a second animal model (using higher level animals such as rabbits) can be used to evaluate the potential applications of the material, such as fixation of fractures or osteotomies or repair of ligaments or cartilage defects. At the same time, the process of material degradation and replacement by host tissues could investigated. If the material functions well enough for fracture fixation or ligament repair in all animal models, then consideration may be given to a cautious, well controlled human trial (Figure 1).1
Cell homing strategy as a promising approach to the vitality of pulp-dentin complexes in endodontic therapy: focus on potential biomaterials
Published in Expert Opinion on Biological Therapy, 2022
Elaheh Dalir Abdolahinia, Zahra Safari, Sayed Soroush Sadat Kachouei, Ramin Zabeti Jahromi, Nastaran Atashkar, Amirreza Karbalaeihasanesfahani, Mahdieh Alipour, Nastaran Hashemzadeh, Simin Sharifi, Solmaz Maleki Dizaj
One of the essential aspects of tissue engineering is the use of biodegradable scaffolds [18]. For tissue engineering, a variety of synthetic or natural polymers and calcium phosphate-based materials have been used. Polyglycolic acid (PGA) was employed as a scaffold in the first work on dental tissue engineering [19]. In addition, collagen sponge scaffolds and collagen gels have recently been found to be effective for tooth regeneration [16,20]. Thus, scaffolds promote cell recruitment, proliferation, and differentiation and serve as a vehicle for bioactive or targeted cells [6,21,22]. These functions may contribute to their capacity to stimulate the revitalization of tooth regeneration. However, there are various alternative scaffold materials available, and knowledge of their effects on tooth regeneration is currently limited [23].
Risk factors for recurrent bleeding from acute hemorrhagic rectal ulcer
Published in Scandinavian Journal of Gastroenterology, 2018
Naoyuki Nishimura, Motowo Mizuno, Yuichi Shimodate, Akira Doi, Hirokazu Mouri, Kazuhiro Matsueda
We found also that although bleeding from AHRU usually ceased spontaneously or with hemostatic treatment, recurrent bleeding was common (30%). Similar or higher rates have been reported by others (24–50%) [3,5,9]. Various methods of endoscopic hemostasis have been used in the treatment of bleeding from AHRU: argon plasma coagulation, forceps coagulation, clipping, hypertonic saline-epinephrine injection, and band ligation [3,5,7]. In the present study, all these methods, plus forceps coagulation, were used singly or in combination, and hemostasis was achieved in most patients. As in previous studies [3,9], we found no significant difference among hemostatic methods used in the rate of recurrent bleeding from AHRU. Second-look colonoscopy has been reported effective for reducing recurrent bleeding from AHRU [9]. In a recent case report, the polyglycolic acid sheet was applied in the attempted promotion of ulcer healing and prevention of recurrent bleeding [12]. The optimal procedure for prevention of recurrent bleeding from AHRU has not been established.
Effect of Cryopreserved Amniotic Membrane on the Mechanical Properties of Skeletal Muscle after Strabismus Surgery in Rabbits
Published in Current Eye Research, 2018
Marta Sierra, Ángel Ortillés, Francisco J Miana-Mena, Jorge Grasa, Begoña Calvo
Animals were intramuscularly anesthetized with medetomidine (0.14 mg/kg, Medeson®; Uranovet, Barcelona, Spain), buprenorphine (0.02 mg/kg, Buprex®; Fort Dodge, Girona, Spain), and ketamine (20 mg/kg, Imalgene 1000®; Merial, Barcelona, Spain), and topically with tetracaine hydrochloride 0.1% and oxybuprocaine 0.4% eye drops (Colircusi anestésico doble®; Alcon Cusi, Barcelona, Spain). A SRM resection described as strabismus treatment was performed in both eyes 24 (Figure 1). First, the muscle was isolated through a conjunctival incision parallel to the limbus followed by dissection (Figure 1A, 1B and 1C). The muscle was secured placing two sutures (temporal and nasal) at 3 mm of the scleral insertion of the muscle (Figure 1D and 1E). Subsequently, 1 mm muscle segment anterior to the sutures was resected (Figure 1E), and the muscle was sutured back to its original insertion site using the sutures previously fixed. An additional suture was placed in the center to ensure a correct apposition of the muscle edges (Figure 1F). All sutures included the full-thickness of the muscle, and scleral or conjunctival passes were avoided. Finally, the conjunctival incision was closed by a continuous suture (Figure 1H). In both procedures, 7/0 absorbable monofilament polyglycolic acid (Sinusorb®; Péters Surgical, Bobigny, France) was used. All surgeries were performed by the same surgeon (A.O.) to avoid inter individual variations.