China
Africa
Explore chapters and articles related to this topic
Phototherapy Using Nanomaterials
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
A. N. Resmi, V. Nair Resmi, C. R. Rekha, V. Nair Lakshmi, Shaiju S. Nazeer, Ramapurath S. Jayasree
Compared to the first-generation PSs, the second-generation PSs showed improvement in tissue accumulation time. Therapy becomes more patient friendly and can be conducted as an outpatient procedure, as the time between PS administration and light irradiation is reduced. Therapy can be carried out on the same day of administration. Photosensitivity window of the second-generation PSs also reduces as they stay less than 2 weeks only in the normal tissue [126]. These PSs with porphyrin ring structures are highly hydrophobic in nature. The degree of PS hydrophobicity has negative influence in the route of administration along with biodistribution/pharmacokinetic profile [122, 139]. Tumor to normal ratio is high for hydrophobic PSs (7:1−8:1) compared to hydrophilic PS (2:1) [140]. Even though hydrophobicity facilitatives the ability to penetrate the cell membrane and locate in the photosensitive sub-cellular compartment, formation of aggregates in aqueous solution is an issue that adversely affect 1O2 generation and photo killing properties. Hydrophobicity can also lead to blood incompatibility and limit the clinical application. These hydrophobic PSs are not soluble in physiological solvents and body fluids that lead to blood incompatibility and limitation in clinical application [141, 142].
Emollient Esters and Oils
Published in Randy Schueller, Perry Romanowski, Conditioning Agents for Hair and Skin, 2020
John Carson, Kevin F. Gallagher
Since we already have an understanding of the effect of variations in the fatty acid hydrochain for the triglycerides, it may be useful to review this information since it applies to the synthetic esters as well. As we increase the hydrocarbon chain length of the fatty acid, keeping the alcohol portion the same, we increase the melting point of the resulting ester. At the same time, we decrease the fluidity and increase the hydrophobicity. This will typically result in an oilier-feeling ester or, if the molecular weight is high enough, an ester with a waxier feel.
Antigens
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Since T cells recognize antigen fragments, T cell epitopes are of the sequential type. Immunodominant T cell epitopes appear to be regions of a protein which are amphipathic (have both hydrophilic and hydrophobic residues) and which are capable of forming helical secondary structure. In particular, a pattern of periodic hydrophobicity appears to be important. That is, within an amphipathic helix, the non-polar residues are all aligned along one edge of the helix (Figure 3–7). Presumably, this would orient the helix such that the lipophilic side would lie in the peptide-binding groove of the MHC molecule (see Figure 8–9) while the polar residues protruded from the surface. Algorithms which detect such recurrent hydrophobicity patterns in primary protein sequences are often (but not always) very successful at predicting which segments will be T cell epitopes. As an example, consider two regions of the Plasmodium falciparum circumsporozoite protein. The two immunodominant helper T cell (Th) epitopes of this molecule are amino acids 326–345 and 361–380 (Table 3–II). The amphipathic nature of these segments is readily apparent, as is some periodicity of hydrophobic residues.
Pullulan based derivatives: synthesis, enhanced physicochemical properties, and applications
Published in Drug Delivery, 2022
Surendra Agrawal, Divya Budhwani, Pravina Gurjar, Darshan Telange, Vijay Lambole
Pullulan can be used to deliver antitumor drugs if it forms the self-assembled nanoparticle in the aqueous phase. For that, modification of pullulan is required by a hydrophobic group such as long carbon chains or cholesterol groups (Yuan et al., 2020). This will result in an amphiphilic polymer that can be processed to form the self-assembled nanoparticle. Pullulan with a hydrophobic group is prepared by binding of cholesterol group to pullulan via monochloroacetate and alkylenediamine in the presence of 1-ethyl-3(3-dimethylamino)-propyl carbodiimide hydrochloride as depicted in Figure 4 (Singh et al., 2015). Nanoparticles of cholesterol-modified pullulan showed higher loading capacity and sustained-release effect. The hydrophobicity of nanoparticles can be changed by altering the degree of substitution of cholesterol. Change in hydrophobicity will affect the size, drug loading, and release from the nanoparticle. Hydrophobicity is directly proportional to drug loading capacity, and drug release from nanoparticles i.e., higher the hydrophobicity, higher will be the drug loading and better sustain release of the drug. It is inversely proportional to the size of the nanoparticle that means an increase in hydrophilicity of pullulan will lead to a small size of the nanoparticle (Yuan et al., 2020).
A thermodynamic study of F108 and F127 block copolymer interactions with liposomes at physiological temperature
Published in Journal of Liposome Research, 2022
Obed Andres Solis-Gonzalez, Juan Ramon Avendaño-Gómez, Aarón Rojas-Aguilar
Another parameter to take into account to explain the partition phenomena in our EYPC/poloxamer systems is that F108 and F127, as members of the poloxamer family, are sensitive to temperature changes. This high sensitivity was also observed in our CMC results. Consequently, an increment in temperature can cause the PPO blocks to become more hydrophobic (Zhang and Lam 2007, Petrov et al.2008). This means that due to its longer hydrophobic (PPO) domain, F127 is less stable as a monomer than F108. Therefore, monomers of F127 have a greater tendency than F108 to stabilise and interact with the lipophilic part of the bilayer, which gives rise to the different partition coefficients of the systems. Indeed, the hydrophobic part of copolymer is the main leading force so as to insert it into the lipid membrane. The hydrophobicity is a strong force that can even overcome unfavourable electric charge repulsions between polymer/liposome interactions of the same charges (Vial et al.2005) or repulsive hydration forces in the fusion event of viruses (Ramalho-Santos et al.1994) for instance. So, the larger the hydrophobicity, the most stable anchoring of the copolymer. This is reflected on the larger partition coefficient and free energy on F127 when compared with F108. In summary, the liquid phase state of the lipid bilayer “enables” the insertion of block copolymers into the bilayer and an increment in temperature enhances this interaction (e.g., from 25 °C to 37 °C) due to an augmentation in hydrophobicity of the PPO block, as temperature rises.
A novel multi-stimuli-responsive theranostic nanomedicine based on Fe3O4@Au nanoparticles against cancer
Published in Drug Development and Industrial Pharmacy, 2020
Bakhshali Massoumi, Amir Farnudiyan‐Habibi, Hossein Derakhshankhah, Hadi Samadian, Rana Jahanban-Esfahlan, Mehdi Jaymand
PNIPAAm exhibits a sharp lower critical solution temperature (LCST) and inverse aqueous solubility with temperature. The LCST of this polymer is around 32–34 °C near human body temperature. The change accrued in response to hydrophilicity–hydrophobicity interactions between polymer chains and water. The LCST value of the PNIPAAm can be manipulated around the body temperature and properly up to 42–43 °C through the various modification approaches (e.g. copolymerization with hydrophilic monomers) [20–22]. In contrast, PAA is the most famous pH-responsive polymer with superior physicochemical properties, including ionization state, reversible variance activity in volume, excellent solubility, and proper balance between the extended and collapsed state in respond to pH change as well as excellent biological features such as biodegradability and biocompatibility, and good instantaneous mucoadhesive properties [23,24].