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Glove Selection for Work with Acrylates Including Those Cured by Ultraviolet, Visible Light, or Electron Beam
Published in Robert N. Phalen, Howard I. Maibach, Protective Gloves for Occupational Use, 2023
More than 50 different acrylic monomers are commercially available and used industrially. They range from monofunctional acrylates (i.e., with one acrylic double bond) to difunctional acrylates (i.e., with two acrylic double bonds) and to multifunctional acrylates (i.e., with three, four, five, or six acrylic double bonds). Table 23.1 provides examples of these main groups of acrylates (acrylic resins or monomers) associated with dermatitis and contact dermatitis, which are discussed in this chapter. They can be divided roughly into two categories: the rather well-defined molecules with narrow molecular weight distribution and the so-called alkoxylated (i.e., ethoxylated and propoxylated) types. The former category is mostly referred to by an acronym, an abbreviation of their chemical name. The more widely used monomers in this category are the following:TPGDA, tripropyleneglycol diacrylateHDDA, 1,6-hexanediol diacrylateTMPTA, trimethylolpropane triacrylate
Engineered Nanoparticles for Drug Delivery in Cancer Therapy *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Tianmeng Sun, Yu Shrike Zhang, Pang Bo, Dong Choon Hyun, Miaoxin Yang, Younan Xia
Several hurdles must be surpassed before polysaccharides can be effectively applied as drug carriers. First, most polysaccharides are of natural origin, and there is a high degree of variability with respect to the molecular weight and structure depending on the source. These properties critically determine the biological activities of polysaccharides, and alternative methods need to be established to produce polysaccharides with consistent properties. Second, the desired effect of the polysaccharides may be counteracted by the biologically active contaminants of polysaccharide, such as endotoxins and pathogens. More effective methods for purifying polysaccharides are urgently needed [225]. Third, the exact mechanisms of the biological actions of most polysaccharides are still unclear. A subtle difference in molecular weight, the arrangement of monomers, and the degree of branching can all result in significant differences in biological activities. A complete understanding of the mechanisms of biological effects is the prerequisite for successful introduction of polysaccharides into nanomedicine applications.
Antibacterial, pH Neutralizing, and Remineralizing Fillers in Polymeric Restorative Materials
Published in Mary Anne S. Melo, Designing Bioactive Polymeric Materials for Restorative Dentistry, 2020
Abdulrahman A. Balhaddad, Maria S. Ibrahim, Michael D. Weir, Hockin H.K. Xu
Another concern is related to the polymerization behavior of these materials. Most of the studies did not investigate important parameters such as degree of conversion, depth of cure, and polymerization shrinkage, which can highlight a better understanding of the polymerization behavior of such materials. Incomplete polymerization is associated with a considerable amount of unreacted monomers. Unreacted monomers have the ability to enhance plaque accumulation and increase the attachment of dental microorganisms. Besides, unreacted monomers may induce a cytotoxic effect on the surrounding dental tissues (Beriat et al. 2010; Mayanagi et al. 2017; Al-Hiyasat et al. 2005). Other concerns are related to biocompatibility and degradation behavior, and very small numbers of the previously discussed bioactive resin composites were subjected to cytotoxicity and degradation tests. Materials with a high amount of cytotoxicity may affect the surrounding tissues inside the oral cavity causing serious complications, and materials with high susceptibility for degradation may detach causing microleakage and restoration failure. To conclude, with a long-term assessment, bioactive resin composites should have a strong antibacterial action, excellent mechanical properties, acceptable polymerization behavior, and low cytotoxicity with no degradation over time.
Potential lipid-based strategies of amphotericin B designed for oral administration in clinical application
Published in Drug Delivery, 2023
Xiaoming Zhong, Jianqiong Yang, Hongyan Liu, Zhiwen Yang, Ping Luo
AmB molecules are divided into three different aggregation states in aqueous media, including monomeric monomers, oligomers or oligo-aggregates, and poly-aggregates (Torrado et al., 2013; Zielińska et al., 2016). Due to its amphiphilic structure and low solubility, AmB tends to aggregate in aqueous solution. AmB monomers exist in water at a very low concentration of 5 × 1 0 −7–1 0 −4 M (Torrado et al., 2013; Zielińska et al., 2016). Above this concentration, AmB molecules occur mostly in the self-aggregated form. Generally, the monomers self-assembled into oligomers or oligo-aggregates form and these into poly-aggregates (Torrado et al., 2013). Oligo-aggregates are usually defined as dimers, even 4 and 8 molecules aggregation of AmB (Zielińska et al., 2016). AmB exhibits four characteristic peaks in the UV absorption spectra i.e., around 407 nm, 385 nm, 365 nm and 344 nm (Torrado et al., 2013; Zielińska et al., 2016). The ratio of the intensity of peak I to peak IV determines the aggregation state of AmB molecules. As reported, the lower ratio of the intensity represents the monomeric state, while its higher ratio confirms molecular aggregates (Thanki et al., 2018).
Sustained release ocular drug delivery systems for glaucoma therapy
Published in Expert Opinion on Drug Delivery, 2023
Zinah K. Al-Qaysi, Ian G. Beadham, Sianne L. Schwikkard, Joseph C. Bear, Ali A. Al-Kinani, Raid G. Alany
Drug release begins immediately upon insertion, and a constant daily dose is delivered continuously over the treatment period. Zero-order release profiles are achieved without any ‘burst’ effect on the first day of treatment. PolyActiva has introduced a technology platform that enables slow drug release, combined with specific drug delivery to the site of action [131]. PolyActiva relies on poly(ester), poly(triazole) or poly(urethane) systems, which biodegrade either alone or in combination to release the active drug. PA5108 composed of latanoprost acid that is covalently attached to a monomeric polymer unit through a labile linker. The precise structure of the polymer or the labile linker to latanoprost acid has not yet been disclosed. Polymerization of the drug-monomer with appropriate co-monomers or polymer segments occurs. The polymer in PA5108 is a polytriazole hydrogel that allows for 20 weeks of medication release before the polymer backbone biodegrades [132]. In a preclinical study on 10 glaucomatous dogs, three different formulations of latanoprost implant including PA5108 were evaluated. IOP was reduced after 10, 19, and 34 weeks compared latanoprost eye drops and placebo implants. The implants were well tolerated with no sign of inflammation [62]. A Phase I safety and tolerance clinical trial is now pending [133].
Surface-modified polymeric nanoparticles for drug delivery to cancer cells
Published in Expert Opinion on Drug Delivery, 2021
Arsalan Ahmed, Shumaila Sarwar, Yong Hu, Muhammad Usman Munir, Muhammad Farrukh Nisar, Fakhera Ikram, Anila Asif, Saeed Ur Rahman, Aqif Anwar Chaudhry, Ihtasham Ur Rehman
Conjugation technique is employed to link two different or similar polymers through a covalent bond (block copolymers). Block copolymers can be formed by either coupling preformed polymers or by in situ polymerization from monomers. In recent years, many coupling agents and conjugating chemistries have been introduced, and several efficient and functional copolymers have been synthesized. Among them, amphiphilic block copolymers, such as polycaprolactone-polyethylene glycol (PCL-PEG) and polylactic-co-glycolic acid-polyethylene glycol (PLGA-PEG) are extensively employed in drug delivery system due to their biocompatibility, low toxicity, and core-shell structure formation in a selective solvent [124]. These nanoparticles consist of hydrophilic corona and hydrophobic drug-loaded core (Figure 4b). The conjugation technique can be further applied to synthesize triblock copolymers and their polymeric nanoparticles. For instance, our research group synthesized polycaprolactone-polyethylene oxide-polycaprolactone (PCL-PEO-PCL) [125] and polycaprolactone-polyethylene oxide-polylactic acid (PCL-PEO-PLA) [126] with different PEG chain lengths to obtain better conformation of the outer layer of nanoparticles. Similarly, targeting agents, such as folic acid, can be conjugated on the surfaces of nanoparticles [127]. Moreover, stimuli-responsive cleavable bonds, e.g., pH sensitive, reduction sensitive, and enzyme sensitive linkages [128] are also inserted in block polymeric nanoparticles via conjugation.