Polymer Template-Directed Synthesis

Abstract

The use of spatially and dimensionally constrained (co)polymers as templates is an effective method to prepare metal nanocrystals. These spatially and dimensionally constrained polymers can serve as reaction cages to control the growth of the particles, leading to the formation of nanoparticles with a morphology complementary to that of the template. By varying the shape of the sacrificial template nanoparticle and its ratio to the more noble metal precursor added, one can obtain a variety of morphologies such as, for example, triangular rings, wires, tubes, boxes, or cages. Block copolymers, especially amphiphilic, have been used to prepare aggregation-free noble metal nanoparticles. New template methods based on a synergistic soft-hard template mechanism were suggested for the preparation of flexible noble metal/cross-linked nanomaterials. Infinite coordination polymer particles are a class of emerging functional materials that are formed by bridging repeating organic ligands with metallic nodes. Noble metal nanoparticles have also been synthesised using biopolymer template such as proteins, nucleic acids, and polysaccharides known as polyelectrolytes. The synthetic polymers known as polyelectrolytes can be used as reducing/stabilizing agents in one single-step syntheses. Highly branched macromolecules-dendrimers are well defined with hollow cores and dense shells. They are constructed from an initiator core to which radially branched layers are covalently attached. Most of the dendritic containers reported so far use the concept of closing the dendritic box in order to keep the guest metal particle inside the dendrimer host. Dendrimer-entrapped nanoparticles are often formed using fast reduction and nucleation chemistry. With PAMAM dendrimers as templates, dendrimer-entrapped metal nanoparticles can be formed with each noble metal nanoparticle entrapped within each dendrimer molecule. Likewise, bimetallic core@shell or alloy dendrimer-(stabilized) entrapped metal nanoparticles can be prepared by coreduction of the metal ions within the dendrimer templates. Colloidally stable and water-soluble functional nanoparticles can be formed with plasmonic and fluorescent activities. The functionalized plasmonic-fluorescent nanoparticles have been used as cell imaging and plasmon-based optical detection probe. Dendrimers find many applications in drug delivery due to the opportunity of their internal niches to host a variety of molecules. They have also been reported to enter tumors and carry either chemotherapeutic agents or genetic therapeutics. Incorporation of photoactive components in either the core or the periphery of these nanostructures enriches them with new functionalities opening new perspectives in nanomedicine.

Glossary

Boltorn polyols

and their derivatives are hyperbranched polymers which are widely used in material and medicinal chemistry to prepare polymers with improved mechanical properties, to modify the properties of membranes, and to control drug delivery. A characteristic example of such hyperbranched molecules, which can now be produced on an industrial scale, belongs to the aliphatic polyester family bearing the commercial name Boltorn^®. The hyperbranched Boltorn polymers can be aliphatic polyesters constructed with ethoxylated pentaerythritol as central cores and 2,2-bis(methylol)propionic acid (bisMPA) as dendritic units. For example, Boltorn H20 should contain 16 hydroxyl end groups per molecule indicating that it contains on average two generations of MPA. Similarly Boltorn H30 and H40, respectively, are third and fourth generation containing 32 hydroxyl and 64 hydroxyl per molecule.

Folic acid

another form of which is known as folate, is one of the B vitamins. It is used as a supplement by women to prevent neural tube defects (NTDs) developing during pregnancy. It is also used to treat anemia caused by folic acid deficiency. Long-term supplementation is also associated with small reductions in the risk of stroke and cardiovascular disease.

Folate targeting is a method utilized in biotechnology for drug delivery purposes. Based on the natural high affinity of folate for the folate receptor protein (FAR), which is commonly expressed on the surface of many human cancers, folate–drug conjugates also bind tightly to the FR and trigger cellular uptake via endocytosis. α_vβ₃ is a type of integrin that is a receptor for vitronectin. It consists of two components, integrin alpha V and integrin beta 3 (CD61), and is expressed by platelets. Furthermore, it is a receptor for phagocytosis on macrophages or dendritic cells.

Hematologic toxicity

is a common treatment complication of chronic hepatitis C virus (HCV) infection, especially when interferon (IFN) and ribavirin are used. The side effects of treatment are often augmented in cancer patients due to baseline cytopenias. These adverse events often lead to dose reduction or discontinuation of antivirals.

Hepatotoxicity

(from hepatic toxicity) implies chemical-driven liver damage. Drug-induced liver injury is a cause of acute and chronic liver disease.

HOMO and LUMO

are acronyms for highest occupied molecular orbital and lowest unoccupied molecular orbital, respectively. The energy difference between the HOMO and LUMO is termed the HOMO–LUMO gap. HOMO and LUMO are sometimes referred to as frontier orbitals. The difference in energy between these two frontier orbitals can be used to predict the strength and stability of transition metal complexes, as well as the colors they produce in solution. Roughly, the HOMO level is to organic semiconductors and that the valence band maximum is to inorganic semiconductors and quantum dots. The same analogy exists between the LUMO level and the conduction band minimum. In organometallic chemistry, the size of the LUMO lobe can help predict where addition to pi ligands will occur. Each molecular orbital has a calculated energy level. Chemists sort the molecular orbitals (MOs) by energy levels. Chemists assume that the electrons will occupy the lowest energy level MOs first. The difference in the HOMO’s energy level and the LUMO’s energy level is called the band gap. The band gap can sometimes serve as a measure of the excitability of the molecule: the smaller the energy, the more easily a molecule’s electrons will be excited. For example, this can help predict whether a substance will have luminescence. As MOs for larger molecules tend to be more complicated (the electrons are spread out all over the big molecule). At this point, we generally no longer focus on a comparison between the MOs and the AOs but instead just take the MOs as a set of orbitals for the whole molecule. There are many such orbitals (an infinite number), but we will always focus simply on the electrons that are most important for the chemistry.

In immunology, the mononuclear phagocyte system or mononuclear phagocytic system (MPS) (also known as the reticuloendothelial system or macrophage system) is a part of the immune system that consists of the phagocytic cells located in reticular connective tissue. The cells are primarily monocytes and macrophages, and they accumulate in lymph nodes and the spleen. The Kupffer cells of the liver and tissue histiocytes are also part of the MPS. The mononuclear phagocyte system and the monocyte macrophage system refer to two different entities, often mistakenly understood as one.

Immunogenicity is the ability of a particular substance, such as an antigen or epitope, to provoke an immune response in the body of a human or animal. In other words, immunogenicity is the ability to induce a humoral and/or cell-mediated immune responses.

Nephrotoxicity is toxicity in the kidneys. It is a poisonous effect of some substances, both toxic chemicals and medications, on renal function. There are various forms, and some drugs may affect renal function in more than one way. Nephrotoxins are substances displaying nephrotoxicity.

Zebra fish

(Danio rerio) is a tropical freshwater fish belonging to the minnow family (Cyprinidae) of the order Cypriniformes.