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Chitosan-Based Nanogels for Biomedical Applications
Published in Vladimir Torchilin, Handbook of Materials for Nanomedicine, 2020
Leyre Pérez-Álvarez, Leire Ruiz-Rubio, José Luis Vilas-Vilela
pH-responsive nanogels can be divided into two types. On the one hand, there exist polycationic-based nanogels that induce drug release at neutral/basic pH values due to the ionization of acidic groups on the polymer chains, such as poly(methacrylic acid), hydroxypropyl methylcellulose phthalate and poly(acrylic acid). On the other hand, it is worth highlighting polycationic nanogels which swell at acidic pH values. The first type of pH-responsive nanogels are typically employed for oral drug delivery because physiological pH shift in the gastrointestinal tract endorses their swelling, while, polycationic nanogels have been used to target tumors, lysosomes and endosomes, where the pH is slightly acid.
Biorefineries
Published in M.R. Riazi, David Chiaramonti, Biofuels Production and Processing Technology, 2017
Isabella De Bari, Daniela Cuna, Nicola Di Fidio, M.R. Riazi, David Chiaramonti
Organic acids and polyhydroxyalkanoates (PHA) will have an important role in the production of renewable plastics. In particular, succinic acid is widely used not only in chemical but also in food and pharmaceutical industries. It can be used in the production of polyesters and polyols for polyurethanes, polybutylene succinate, plasticizers, 1-4 butanediol, composite resins for packaging, footwear, clothing, plastic films, and interiors of cars. Lactic acid is the precursor of polylactic acid (PLA) used for the preparation of biodegradable plastic. Acrylic acid and its esters readily combine to form polyacrylic acid or other monomers (e.g., acrylamides, acrylonitrile, vinyl, styrene, and butadiene). The resulting homopolymers or copolymers are used in the manufacture of various plastics, coatings, adhesives, fibers and textiles, resins, and elastomers (synthetic rubbers). Around 85%–90% of adipic acid is used as monomer in the production of nylon 6-6, or it is further processed into fibers (polyurethanes, adipic esters) for applications in carpeting, automobile tire cord, and clothing. Adipic acid is also used to manufacture plasticizers and synthetic lubricant components. Polyhydroxybutyrate (PHB) and polyhydroxyvalerate are common types of PHAs available in nature. Depending on its grade, PHB is similar in the mechanical, physical, and thermal properties to many different plastics, including, for instance, polypropylene, polyethylene, and polystyrene (Petersen et al. 2001). It is currently used in the medical industry for internal suture as it is nontoxic, compatible, and naturally absorbed. Other potential uses are as capsules in pharmacology and packaging (Saharan et al. 2014).
Study of a cross-linked hydrogel of Karaya gum and Starch as a controlled drug delivery system
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Sapna Sethi, Balbir Singh Kaith, Mandeep Kaur, Neeraj Sharma, Sadhika Khullar
Starch is a semi-crystalline polymer composed of two polysaccharide units, linear amylose and branched amylopectin [10]. Starch as an economical and biodegradable material obtained from renewable resources is a potential candidate for developing such sustainable and environmental friendly materials. Starch can be chemically cross-linked to karaya gum to improve thermal and mechanical properties of hydrogels. Generally, the acrylic acid moieties are grafted over natural polymers and then grafted polymer backbones are cross-linked to synthesize hydrogels. Polyacrylic acid grafted hydrogels are hydrophilic, pH responsive and have potential to deliver the water soluble drugs to specific sites in the body [11]. The polysaccharides have always been considered as potential oral drug carriers due to their availability, easy modification, stability, safety and biodegradability [12]. Aspirin and paracetamol are widely used antipyretic and analgesic drugs with anti-inflammatory activity. The direct oral intake of these drugs may cause irritation of gastrointestinal tract, heartburn, gastritis, liver impairment etc. [13]. These drugs if loaded in hydrogel matrix can be safely delivered to body without causing any type of irritation, toxicity and other side effects.
A novel gold nanorods-based pH-sensitive thiol-ended triblock copolymer for chemo-photothermo therapy of cancer cells
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Somayyeh Fallah iri sofla, Mojtaba Abbasian, Mortaza Mirzaei
The self-assembly behavior of the AuNRs@polymer was investigated by means of DLS measurements at various pHs. It is well established that poly acrylic acid demonstrates different hydrophilicity or hydrophobicity depend on protonation or deprotonation of its carboxyl groups in different pH solutions. Hence, PAA block in PAA-b-PDMAEMAQ-b-PCL-SH triblock copolymer can influence the size and size distribution of the AuNRs@polymer. In acidic solutions (pH <4.2) the formation of micelles with PCL, PAA, and PDMAEMAQ as core, shell, and coronas respectively. In addition, in all ranges of pHs the PCL segment placed as the core is expected. In contrast, at higher pH values (pH >4.2) the formation of micelles with PCL, PDMAEMAQ, and PAA as core, shell, and coronas, respectively is preferred, principally due to deprotonation of the carboxyl groups in the PAA section. According to these facts, the mean diameters of the of micelles decreased from initial 243 to 171 nm when pH decreased from initial 4.50 to 3.50, which was likely due to the hydrogen bonding within the protonated PAA outer shell. When the pH increased to 5.50 and 7.4 the mean diameters of the micelles escalated from 243 to 344 and 400 nm respectively, in part due to the intramicellar increasing electrostatic repulsion between PAA outer shells, caused by the deprotonation of carboxyl groups [52]. (Figure 6).