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Design of Bioresponsive Polymers
Published in Deepa H. Patel, Bioresponsive Polymers, 2020
Anita Patel, Jayvadan K. Patel, Deepa H. Patel
The polymerization controls given by ATRP are an effect of the radical’s formation which can grow; however, they are reversibly deactivated forming dormant species (see Figure 2.1) [20]. Dormant species reactivation permits on behalf of the polymer chains to grow up another time, merely deactivated afterward. That kind of progression consequences in a polymer chain that gradually, nevertheless progressively, grow, and have a distinct end group (generally, an alkyl halide is ending group for ATRP).
Pharmacology of Therapeutic Agents in Photomedicine
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
Ira C. Davis, Matthew J. Stiller, Jerome L. Shupack
Three generations of retinoids have been developed based on modifications of the prototype vitamin A molecule (Fig. 6) (55). The first-generation retinoids, including isotretinoin and all-trans-retinoic acid, were synthesized by altering the polar end group and polyene side chain. The second generation, aromatic retinoids, etretinate and etretin, were formed by modifying the cyclic end group. Arotenoids, the third generation of retinoids were derived by cyclizing the polyene side chain.
PEGylated Dendritic Nanoparticulate Carriers of Anti-Cancer Drugs
Published in Mansoor M. Amiji, Nanotechnology for Cancer Therapy, 2006
D. Bhadra, S. Bhadra, N. K. Jain
One very important derivative that has been used in number of derivatisation reactions that has one hydroxyl group blocked is monomethyl-ether of polyethylene-glycol or monomethoxy-polyethylene-glycol (MPEG), i.e., considered equivalent in terms of reaction for formation of PEG derivatives. This was generally brought in use for conjugation to bioactive species. It is generally used when multiple chains of polymers had to be linked to the intended substrates. Because of structural simplicity and possession of only one-derivatizable end group, the use of MPEG minimizes cross-linking possibilities and leads to improved homogeneity of conjugate. Therefore, it usually is a starting material of choice for the covalent modification of proteins, biomaterials, particulates, lipids, drugs, etc. (Zalipsky 1995).
An overview of PLGA in-situ forming implants based on solvent exchange technique: effect of formulation components and characterization
Published in Pharmaceutical Development and Technology, 2021
Tarek Metwally Ibrahim, Nagia Ahmed El-Megrab, Hanan Mohammed El-Nahas
Another parameter that can control the PLGA hydrophobicity is the type of chemical moieties present at the end of polymeric chains either end-capped with free carboxylic acids or esters (Lanao et al. 2013). Where, polymers of the ester end group are relatively more hydrophobic than acid end group ones. Wang et al. (2020) pointed out that utilization of ester-capped PLGA polymer can slow down the release rate and sustain the release period of the drug, whereas the acid-terminated PLGA facilitated much faster drug release. In addition, the end-capping of PLGA chains has a marked impact on the type of solvent used in the preparation of ISFI systems. For example, ester-capped PLGA polymers are insoluble in hydrophilic solvents and need more hydrophobic solvents to provide optimal solubility of the polymer and successful development of the ISFI systems (Jivawala and Goyani 2017).
How subtle differences in polymer molecular weight affect doxorubicin-loaded PLGA nanoparticles degradation and drug release
Published in Journal of Microencapsulation, 2020
Natalya Kumskova, Yulia Ermolenko, Nadezhda Osipova, Aleksey Semyonkin, Natalia Kildeeva, Marina Gorshkova, Andrey Kovalskii, Tatyana Kovshova, Vadim Tarasov, Joerg Kreuter, Olga Maksimenko, Svetlana Gelperina
As mentioned above, the performance of the PLGA nanoparticles as drug delivery systems relies to a great extent on the properties of the polymer. However, researchers conducting studies of PLGA nanoparticles very rarely specify the precise characteristics of the polymers they have used in their experiments. The manufacturers’ data are generally limited to the polymer composition (lactide–glycolide ratio) and the chemical structure of an end group (ester or carboxyl end group). There is no common standard as to the indication of the polymer’s molecular weight: either intrinsic viscosity or – more often – inherent viscosity of the polymer solution measured under given conditions or a molecular weight range are indicated. While most of the authors do not leave out these essential parameters, other parameters such as the acid value (AV), a parameter characterising the number of available carboxylic groups at the nanoparticle surface, as well as the residual monomer content are rarely mentioned in the publications. At the same time, these latter parameters are very important and can have a drastic effect on the properties of the nanoparticulate drug formulation.
Biodegradable composite porous poly(dl -lactide-co-glycolide) scaffold supports mesenchymal stem cell differentiation and calcium phosphate deposition
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Serena Casagrande, Roberto Tiribuzi, Emanuele Cassetti, Francesca Selmin, Gian Luca Gervasi, Lanfranco Barberini, Marco Freddolini, Maurizio Ricci, Aurélie Schoubben, Giuliano G. Cerulli, Paolo Blasi
In the case of coated scaffolds, the accuracy of GPC analysis was compromised, probably by the presence of residual CH coating that could not be completely removed. Indeed, ATR-FTIR data confirmed the presence of an interaction between the PLGA scaffold and the coating. It can be assumed that CH chains, which are positively charged, can form electrostatic interactions with the PLGA negatively charged surface. This feature is in agreement with the model proposed by Guo and Gemeinhart. The adsorption of chitosan follows a multilayer adsorption behaviour suggesting that the adsorption of chitosan occurred on an energetically heterogeneous surface. Chemical heterogeneity (the distribution of carboxylic end group and intermediate segments of PLGA molecules) could also contribute to this interaction [30].