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Two-dimensional and Three-dimensional Dosimetry
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Mark Oldham, Devon Godfrey, Titania Juang, Andrew Thomas
Polymer gels belong to another class of dosimeters created with an aqueous gel-based matrix. The mechanism of dose response for these dosimeters is radiation-induced polymerisation of vinyl monomers (e.g. acrylamide, N,N'-methylene-bis-acrylamide, acrylic acid or methacrylic acid) through reaction with free radicals generated within the gel from water ionisation (Oldham 2014; Baldock et al. 2010). The polymerisation reaction results in the formation of polymer microparticles which have a density which increases in proportion to the dose. Since these polymer microparticles have the property of scattering visible light, irradiated portions of a polymer gel dosimeter are visible to the naked eye, exhibiting an opaque, clouded appearance. Readout can be performed with MRI, x-ray CT or optical CT.
Spray Drying and Pharmaceutical Applications
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
Metin Çelik, Pavan Muttil, Gülşilan Binzet, Susan C. Wendell
One specific polymer type that has been employed in the spray drying of drugs to modify its release is acrylic resin. A commercial blend of neutral methacrylic acid esters was used for the preparation of spray dried controlled-release microcapsules containing model drugs [62]. The dissolution results of tablets compressed from these microspheres showed successful controlled release with advantages over a matrix system. In a similar study, sustained release and enteric tablets were prepared by directly compressing spray dried microspheres produced using different types of acrylic resins [63]. Complete enteric properties were observed for tablets made from pH-dependent, anionic acrylic polymers while a sustained release profile was observed for tablets made from microspheres containing pH-dependent, cationic acrylic polymers.
Alternative Tumor-Targeting Strategies
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
One example of this approach developed by Zhao and co-workers utilized two types of polymeric micelles made from two different amphiphilic Block Co-Polymers (BCPs), of which the hydrophobic block was a polymethacrylate that contained either o-nitrobenzyl or coumarin molecules which exhibit two-photon absorption of NIR light. It was demonstrated that upon exposure to NIR light, absorption photolysis of the chromophores was induced, resulting in their conversion from polymethacrylate to the more hydrophilic poly(methacrylic acid), leading to irreversible disruption of the micelles and release of their drug cargo.
Biomedical Applications of polymeric micelles in the treatment of diabetes mellitus: Current success and future approaches
Published in Expert Opinion on Drug Delivery, 2022
Jaskiran Kaur, Monica Gulati, Flavia Zacconi, Harish Dureja, Raimar Loebenberg, Md Salahuddin Ansari, Othman AlOmeir, Aftab Alam, Dinesh Kumar Chellappan, Gaurav Gupta, Niraj Kumar Jha, Terezinha de Jesus Andreoli Pinto, Andrew Morris, Yahya E. Choonara, Jon Adams, Kamal Dua, Sachin Kumar Singh
For instance, Hu et al. reported the formation of pH-responsive cationic polymeric micelles (PCPMs) formed from poly(methyl methacrylate-co-methacrylic acid)-block-poly(2-amino ethyl methacrylate) for oral insulin delivery. The PCPMs exhibited sharp pH-sensitive behavior with a change in particle size, allowing for an increased absorption of insulin in the gastrointestinal tract. An increase in pH from 1.8 to 6.0 showed a decrease in size while the progressive elevation in pH from 6.0 to 7.4 resulted in and increased size. This was attributed to the increased ionization of the methacrylic acid segments with an increase in the neutral pH-range, inducing swelling of PCPMs. The swollen PCPMs released the loaded insulin at pH 7.4 in a sustained manner (more than 50%) as compared to pH 1.2 (30%) over a period of 6 h showing a low burst release of insulin at acidic pH without any cytotoxicity against Caco-2 cells [125].
Effect of substitution of plasticizer dibutyl phthalate with dibutyl sebacate on Eudragit® RS30D drug release rate control
Published in Pharmaceutical Development and Technology, 2019
Rakesh Singh Chaudhary, Tejas Patel, Job Richard Kumar, Mohamed Chan
Acrylic Acid polymers are widely used in the film coating of pharmaceutical dosage forms for a variety of functional and non-functional usage, e.g. moisture protection, gastric acid resistance, taste masking, and to control the drug release in the controlled release dosage form. For controlling the drug release by barrier film formed on the dosage form consists of film forming polymer, insoluble fillers such as colors, opacifiers, plasticizers, and solvent. For the controlled release dosage form, where the drug release is controlled by the polymer film, use of methacrylic acid derivative is often used. The presence of plasticize in film coating formulations has an important role in providing increased elasticity and flexibility to the film formed (Godwin 2000). The use of plasticizer in polymeric solution or dispersions for film coating allows to increase the workability, flexibility, and reduced tensile strength of the polymer by modifying thermal and mechanical properties of the polymer (Rowe et al. 1984; Bodmeier and Paeratakul 1994). The plasticizers in polymeric dispersion during plasticization, partition into and soften the colloidal polymeric particles and promote particle deformation to enable coalescence into a homogenous film. The plasticization effect is dependent on the plasticizer–polymer compatibility and the plasticizer performance in the film during coating, storage, and during contact with artificial or biological fluids.
Eudragit S100 coated microsponges for Colon targeting of prednisolone
Published in Drug Development and Industrial Pharmacy, 2018
Amrita Kumari, Ankit Jain, Pooja Hurkat, Ankita Tiwari, Sanjay K. Jain
Eudragit S 100 (ES) is one of the most employed enteric polymers for colon targeting of drugs. It is a copolymer of methacrylic acid and methyl methacrylate. It is pH responsive and protects MDS from degradation in hostile gastric milieu (low pH and enzymes) and effectively delivering drug to the distal part of intestinal region [15,16]. Hence, we developed prednisolone loaded microsponges (PLM) which were compressed into tablets and coated with ES for safe and effective colon-specific drug delivery to manage the inflammation in case of IBD. This approach not only increases the bioavailability of the drug but also reduces the dose and side effects of the drug. Microsponges also protect the drug from the hostile environment of upper gastro-intestinal tract and release the drug at the inflamed colonic site.