Tissue engineering
John Dudley Langdon, Mohan Francis Patel, Robert Andrew Ord, Peter Brennan in Operative Oral and Maxillofacial Surgery, 2017
The underlying hard tissues offer the framework for overlying facial aesthetics, as defects in osseous and cartilaginous tissues are visibly portrayed through the soft tissues. Classically, significant morbidity and deformity is traded in a distant donor area for reconstruction of craniofacial structures. Allogeneic grafts are available; however, in order to achieve minimal immunologic response, all cellular tissues are removed reducing the potential for reliable integration. Lastly, alloplastic materials are at risk for foreign body reaction, with significant inflammation and increased risk of infection. Tissue-engineered scaffolds have been created to capitalize on a patient’s innate healing response while adding specific factors at the local site to attempt to improve hard tissue regeneration. Tissue engineering has explored a number of materials for creation of scaffolds including polymers, ceramics and composites. Polymers (polylactic acid, polyglycolic acid, polycaprolactone, polypropylene fumarate) have variable properties and offer reliable biodegradation. More permanent ceramics (hydroxyapetite, tricalcium phosphate) can be used alone, but are frequently combined with polymers in composite grafts. Composites can also include biofactors such as purified concentrated growth factors, transduced cells with various viral vectors, and autogenous bone marrow cells.
The Mirage microfiber sirolimus eluting coronary scaffold
Yoshinobu Onuma, Patrick W.J.C. Serruys in Bioresorbable Scaffolds, 2017
The MMSES is a coil-like structure with three longitudinal supporting monofilaments. It is made of mechanically strengthened polylactide (PLA) monofilament. The high mechanical strength of PLA monofilament results in the high radial strength of MMSES. Circular monofilaments in diameter of 125 and 150 μm are used for building scaffolds with diameter less or equal to 3.0 mm and greater or equal to 3.5 mm, respectively. Circular geometry of PLA monofilament is also well preserved in MMSES. MMSES has a circular strut that is believed to accelerate the re-endothelialization process and minimize the risk for scaffold thrombosis [1]. PLA monofilament technology offers great flexibility in manufacturing bioresorbable scaffolds. MMSES was made into various sizes that were virtually the same as those in DESs. In this study, MMSES were used for lesions with reference diameters from 2.27 to 4.0 mm and length ≤48 mm. Scaffolds of 10 sizes, i.e., 2.5 × 18, 2.5 × 28, 2.75 × 18, 2.75 × 28, 3.0 × 18, 3.0 × 28, 3.5 × 18, 3.5 × 28, 4.0 × 18, and 4.0 × 28 mm, were supplied for this trial.
Applications of Nanoparticles in the Treatment of Gliomas
Hala Gali-Muhtasib, Racha Chouaib in Nanoparticle Drug Delivery Systems for Cancer Treatment, 2020
Polymer NPs have dimensions ranging from 10 to 1000 nm in diameter. They consist of natural or synthetic polymers; among the first being cellulose, alginate, gliadin; and among the second polylactide (PLA), and poly-(lactide-co-glycolide) (PLGA). In general, synthetic polymers are preferred since their chemical-physical properties, such as solubility or permeability, can be easily quantified. Polymeric NPs can convey a large amount of therapeutic agents, both hydrophilic and lipophilic, both high and low molecular weight (e.g., DNA or antisense oligonucleotides) [2]. The techniques of synthesis of polymeric NPs are different and include adsorption, entrapment, encapsulation, and dissolution. Based on the technique used, we distinguish nanospheres and nanocapsules. In nanospheres, the drugs are entrapped or adsorbed within the polymers, while in nanocapsules the medications are inside the liquid core surrounded by the polymeric membrane. Polymer particles can also be used to coat other NPs; for example, the hydrophilic PEG prevents the recognition of NPs by the endothelial systems and its phagocytosis; hydrogel and dextran guarantee an increase in the plasma half-life of drugs [2]. The disadvantages of polymeric NPs relate to the complexity and the cost of preparation and the concrete possibility of triggering immune responses and allergic reactions [41].
Synthetic biodegradable polyesters for implantable controlled-release devices
Published in Expert Opinion on Drug Delivery, 2022
Jinal U. Pothupitiya, Christy Zheng, W. Mark Saltzman
Polylactide (PLA) or polylactic acid is a biodegradable polyester, which is extensively used in the textile, packaging, and biomedical industries. Polylactide is synthesized from lactide monomers and polylactic acid from lactic acid. The widespread use of PLA is attributed to its relatively simple bulk production methods, high abundance, recyclability, composability, and mechanical strength (which is comparable to polystyrene). Furthermore, the long history of PLA use in implanted devices – and its well-characterized biodegradability – make it an attractive material for biomedical implants. PLA is synthesized from lactic acid or lactide, which are monomers derived from renewable resources such as corn, wheat, carbon dioxide, and rice. The polymer degrades in biological systems by hydrolysis and enzymatic activity to produce lactic acid, which is a natural metabolite in the body. PLA is generally recognized as safe; it is a component in many FDA-approved products [2,111,112].
The role of additive manufacturing and antimicrobial polymers in the COVID-19 pandemic
Published in Expert Review of Medical Devices, 2020
The development of an affective antimicrobial polymer for additive manufacturing seems increasingly critical due to the extensive used of polymers in the prototyping of critical medical devices. It has been suggested [12] that the addition of nanoparticles of copper to polymers and the resulting antimicrobial properties have promising applications to the development of medical devices associated to bacterial growth [12]. Previous investigations have used copper nanocomposites to enhance the antimicrobial properties of polymers used in injection molding and additive manufacturing to develop medical device [9,11] Currently, the most commonly used polymer in additive manufacturing is polylactic acid. Polylactic acid has been described as the main commodity polymer derived from annually renewable resources, such as corn [13]. Thus, the use of a renewable resource to produce antimicrobial polymers for additive manufacturing could significantly assist the current medical product supply chain disruptions involving the manufacturing of critical medical devices in austere clinical settings.
A polymer–lipid membrane artificial cell nanocarrier containing enzyme–oxygen biotherapeutic inhibits the growth of B16F10 melanoma in 3D culture and in a mouse model
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Yun Wang, Thomas Ming Swi Chang
The editorial also mentioned the problem that with intravenous administration of different drug carrier systems, the delivery efficiency was less than 1% [4]. In the present study of local injection, the nanoencapsulation efficiency of PH-TYR into the nanocarrier is 75.4% [16,17]. In the present report, by administrating this locally, most of this reached the site of injection. Analysis at the site of injection showed a small foreign body granular containing the nanocarriers with no inflammation. With time the polylactide–lipid will be biodegraded. Decreasing the molecular weight of the polylactide would increase the rate of biodegradation of the polymer. The content of PH-TYR will be metabolized like another of our enzyme–oxygen therapeutic poly-[haemoglobin–catalase–superoxide dismutase-carbonic anhydrase] that did not show any safety or immunological problem [21] and is now under development for clinical trial.
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