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Effects of Thermal Cycling on Surface Hardness, Diametral Tensile Strength and Porosity of an Organically Modified Ceramic (ORMOCER)-Based Visible Light Cure Dental Restorative Resin
Published in P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas, Advanced Studies in Experimental and Clinical Medicine, 2021
Our previous studies [18] showed that the selection of photo-initiator has a significant effect on monomer conversion and clinical performance. Compared to CQ/amine, photo-polymerization of BisGMA is found to be more efficient with TPO. Both exposure and storage times were important variables in CQ/amine, but not in TPO. Free radicals generated by CQ/Amine showed more radiative and nonradiative energy loss compared to TPO photolysis. The better monomer conversion of TPO based system reduces the adverse toxicological effects due to chemical and mechanical degradation.
Methods for Characterization of Bioactivity Using Confocal Microscopy *
Published in Mary Anne S. Melo, Designing Bioactive Polymeric Materials for Restorative Dentistry, 2020
Jirun Sun, Joy P. Dunkers, Sheng Lin-Gibson, Nancy J. Lin
Ethoxylated bisphenol-A dimethacrylate (EDMA, degree of ethoxylation ≈ 6), was obtained from Esstech, Inc. Camphorquinone (CQ) and ethyl 4-N,N-dimethylaminobenzoate (4E) were purchased from Aldrich Corp. All reagents were used as received. The resin monomer was activated with a redox photoinitiator system consisting of 0.2% CQ and 0.8% 4E (by mass), and stored in the dark until use. Sodium chloride crystals were ground into small particles using a mortar and pestle and then separated into defined size ranges using brass sieves.
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
Another way to activate the hardening effect in the injectable paste at targeted site is use of ultraviolet (UV) light. Si doped HAp nanopowder incorporated photocurable aligate paste was prepared for orthopaedic application. Si doped HAp nanopowder incorporated alginate-based paste showed good injectability and hardened after UV exposure to generate a sparsely porous matrix (Gupta 2018). However, the chromosomal and genetic instability of exposed cells possess concern while using the UV lights for photo-polymerization (Dahle et al. 2005, Kappes et al. 2006). Care should also be taken with use of toxic photoinitiator or intense UV light irradiation along with these cell-encapsulated pastes as they can lead to cell damage.
Gelatin-methacryloyl hydrogel based in vitro blood–brain barrier model for studying breast cancer-associated brain metastasis
Published in Pharmaceutical Development and Technology, 2021
Robin Augustine, Alap Ali Zahid, Fatima Mraiche, Khurshid Alam, Ala-Eddin Al Moustafa, Anwarul Hasan
Polymer solution was prepared by dissolving GelMA (2.5% or 5% w/v) in DPBS. 2-hydroxy-1-(4-(hydroxyethoxy)phenyl)-2-methyl-1-propanone (0.5% w/v, Irgacure 2959, CIBA Chemicals) was as used as the photoinitiator. As the first step of fabrication, we used various amounts of GelMA solution over the transwell membrane in order to form a thin coating, a slightly thicker one ∼50 μl and a thicker coating of ∼100 μl of the GelMA solution over the transwell insert. The GelMA solution was then allowed to infiltrate through the pores of transwell membranes for 1 min, and photo-crosslinked by exposure to UV for 3–10 s using a UV chamber (500 nm wavelength, 7 mW/cm2, Ommicure S1000). The GelMA-Transwell assemblies were then washed several times in DPBS to remove unreacted reagents. Samples were dried by serially dehydrating in alcohol and used for characterizing the morphology and weight gain upon coating.
Synthesis of high payload nanohydrogels for the ecapsulation of hydrophilic molecules via inverse miniemulsion polymerization: caffeine as a case study
Published in Drug Development and Industrial Pharmacy, 2019
Fiora Artusio, Ada Ferri, Valeria Gigante, Daniele Massella, Italo Mazzarino, Marco Sangermano, Antonello Barresi, Roberto Pisano
Concerning the differences in the plateau quantity of released caffeine, some considerations must be done. It is indeed well known that caffeine molecules undergo degradation under UV irradiation. Such an issue is quite common to several drug molecules and sometimes limits the shelf life of pharmaceutical formulations. Given the use of UV light in the synthesis of the nanocarriers, the potential degradation of the caffeine molecules had been initially assessed by spectrophotometry. After UV irradiation of a solution of caffeine, using the same operating conditions used for the encapsulation process, we observed a decrease of about 40% in the absorbance peak at 273 nm. Conversely, when photoinitiator was added to the solution according to the ratios used in the nanohydrogel synthesis, the decrease in caffeine absorbance turned out to be around 1%. Therefore, the photoinitiator had a vital role as concerns the protection of the active ingredient from UV degradation. These results suggest that our encapsulation process allows the protection of the drug molecule from external factors that could degrade it and is in agreement with the findings of Bazzano et al. [49] who successfully employed this approach to incorporate an even more UV-sensitive drug such as curcumin. Instead, the amount of drug released by the caffeine-loaded miniemulsion is lower and this is ascribed to the absence of the photoinitiator in the emulsion and therefore of UV protection.
3D printing of oral drugs: a new reality or hype?
Published in Expert Opinion on Drug Delivery, 2018
Wen-Kai Hsiao, Barbara Lorber, Herbert Reitsamer, Johannes Khinast
3DP technologies can be classified by the physical mechanisms used to consolidate materials into layers. The main approaches include photochemical and thermal transformation, as well as binding/adhesion. Prominent 3DP techniques include stereolithography (SLA) [1], inkjet-powder bed [2], and material extrusion, including fused deposition modeling (FDM) [3]. Table 1 summarizes their key attributes and applications for producing oral solid dosage forms (OSDF). Clearly, the main techniques used are inkjet-powder bed and FDM. This is likely due to the intrinsic material limitation of the other 3DP processes. For example, although SLA and FDM can both process polymeric materials, they do so in very different fashions. Whereas FDM creates layers by melting and re-solidifying polymer filaments, SLA does so by photo-polymerization, a process in which a liquid mixture of monomers, oligomers, and photo-initiators is activated by light and cross-linked into solids. However, the activation process often decomposes the photo-initiators into reactive species which can create stability and toxicity concerns, complicating formulation design.