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Radiometry
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Organic materials consist mainly of carbon and hydrogen atoms and thus have an atomic composition close to that of tissue, which is useful when the detectors are used for dosimetry. Due to the approximate tissue equivalence, the cross section for photon interactions is similar to that in water or soft tissue. Many of these materials can also be mixed with liquids and plastics, which make it possible to produce detectors that can be fairly large. For example, plastic scintillators are often utilized in portal monitors that are used to monitor passing vehicles for radioactive elements. The large detector volume will then compensate for the comparatively low counting efficiency, due to the low-Z materials in the organic molecules.
A Brief Background
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
Life is based on carbon. Organic chemistry is dedicated to this element, whose properties are defined by the nature of the carbon atom. Carbon is in group 4 of the periodic table, which identifies that there are four valence electrons. These are the outer electrons involved in bonding, so a further four electrons are required through bonding to other atoms to satisfy the octet rule; hence, carbon atoms characteristically form four covalent bonds, and each bond comprise of shared pairs of electrons with partner atoms. These may be single bonds, with one shared pair of electrons, or double bonds and even triple bonds, with two and three pairs of electrons being shared. It is common for carbon atoms to bond together in chains and rings to produce the carbon skeleton that defines an organic molecule; the remaining valences are often satisfied by hydrogen atoms, which offer their single electron to form a bonding pair. This produces the simplest class of organic compounds: hydrocarbons, typically separated according to molecular mass through fractional distillation of crude oil.
Sunscreens
Published in Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters, Cosmetic Formulation, 2019
Sunscreens can be categorized in a variety of ways. The most common is to split them into two sections depending on how they work. The first, and largest, group is frequently referred to as chemical or organic filters and their mode of action is absorption (Figure 17.1 ). They are typically large organic molecules with multiple unsaturated bonds. When subjected to UV radiation the molecule absorbs the photon(s), which increases the energy of the molecule from the ground state to the higher level of energy called an excited state. The molecule will then attempt to return to the lower energy ground state level and, if successful, returns back to the same form it was in prior to irradiation, ejects the extra energy as infrared radiation, and is ready to receive more photons and continue the cycle once more.
Therapeutic and cosmetic applications of mangiferin: an updated patent review (patents published after 2013)
Published in Expert Opinion on Therapeutic Patents, 2019
Farha Quadri, Manasi Telang, Anita Mandhare
Most organic molecules form various crystalline structures; a polymorph refers to one of the well-defined crystalline structures where the molecules are attached to each other in a ‘repeatable pattern’. The active ingredient might be present in different polymorphic forms [43]. Different polymorphs have different stability, which depends on the ‘strength of attachment’ to the neighbor molecules. In development of a pharmaceutical drug, it is usually desired to use the most stable polymorph to avoid the risk of transformation into another form. The more stable polymorph has a lower solubility and dissolution rate. Different polymorphic forms can be produced by exposing the molecule to different crystallization conditions. According to regulatory guidelines a polymorph screening is required to get a new drug approved [43].
Responsive polymer conjugates for drug delivery applications: recent advances in bioconjugation methodologies
Published in Journal of Drug Targeting, 2019
Daniel Cristian Ferreira Soares, Caroline Mari Ramos Oda, Liziane Oliveira Fonseca Monteiro, Andre Luis Branco de Barros, Marli Luiza Tebaldi
The use of polymers in designing prodrugs to enhance the efficacy, pharmacokinetics and biodistribution profiles of a series of delivery systems has been extensively explored in the last few decades [1–4]. A number of organic molecules used clinically, including proteins, have emerged as attractive therapeutic agents. However, existing methods of administering these therapeutic agents result in toxicity to healthy human body cells and other undesirable side effects [5–7]. Improving the efficacy of therapeutic molecules, by focussing on the delivery platform or vehicle, rather than the drug itself is an emerging and challenging area of opportunity in modern medicine. Despite many efforts and progress, advancement in combining structure, versatility and adaptability to achieve an effective administering vehicle remains far from being a practical reality [5–10].
Emerging PEGylated non-biologic drugs
Published in Expert Opinion on Emerging Drugs, 2019
Eun Ji Park, Jiyoung Choi, Kang Choon Lee, Dong Hee Na
Protein-based biopharmaceuticals have been the most actively studied targets for PEGylation and therapeutics in various classes, including enzymes, interferons, granulocyte-colony stimulating factors, hormones, antibody fragments, and coagulation factors, are available on the market (Table 1). In the development of these protein-based drugs, PEGylation conferred several in vitro and in vivo advantages to the linked proteins, such as extended circulation half-life, improved aqueous solubility, enhanced stability against proteolytic enzymes, and reductions in toxicity and immunogenicity. These advantages could be applied to relatively small sized non-protein drugs, such as small organic molecules, synthetic peptides, and aptamers. However, these non-protein drugs may require different aspects to be assessed from protein drugs, based on their physicochemical properties and applications.