In general terms, a vector consists of a nanocontainer, in which the therapeutic substance is loaded, and a system for targeted delivery, located on the outer surface of the nanocontainer. In some cases (nano-conjugates, Janus particles, nanosomes, multi-functional nanoparticles in medicine) this system of targeted delivery (especially for molecular engineering in bio-pharmacology) is also called a vector. Nanomaterials used in production of vectors include nanoparticles of biocompatible linear polymers (polyethylene glycol, polylactic acid, etc.) and branched polymers (dendrimers), liposomes, as well as replication-defective viral particles. Research is now underway into the prospect of using fullerenes, nanotubes and other non-biological nano-objects, modified to render them biocompatible. An example of such modification is pegylation, i.e. the attachment of polyethylene glycol (PEG) to a nanoparticle surface. For the purpose of targeting, nanocontainers are modified by molecules that recognize surface receptors of target cells, such as antibodies, folic acid, etc.
Vectors for drugs delivery systems without nanocontainers have been developed with the targeting molecule attached directly to an individual drug molecule. For example, a hybrid molecule consisting of an antibody to cell surface ferritin receptor and biotin-binding protein avidin has been created using genetic engineering techniques. Chemical biotinylation (modification by biotin) of active pharmaceutical ingeredients to be delivered ensures their strong binding to avidin. Then, the delivery of the drug to the cells, in particular, to the cells of central nervous system, is achieved by active transport through the endothelium of brain capillaries.
High accumulation of nanocontainers loaded with drugs in some organs (liver, lungs, spleen) can be achieved even without specific targeting due to the natural barrier function of these organs. Nanocontainer accumulation also occurs in tumours due to the high permeability of tumour microvessels, which allows even larger molecules and particles from the blood to pass easily into the extravascular extracellular space. However, the difference in accumulation of therapeutic agents in the tumour and in healthy tissue is often low, therefore the development of highly specific targeted molecules, or other targeting methods, are required to turn the vectors into high-precision "magic bullets".
Potential nanocontainers for medications. Equipped with a precise delivery system, such nanocontainers become vectors.
- Shirinsky Vladimir P.
- Rajesh S., James W., Lillard Jr. Nanoparticle-based targeted drug delivery // Experimental and Molecular Pathology. 2009. V. 86. P. 215–223.
- Kaparissides C., Alexandridou S., Kotti K., Chaitidou S. Recent Advances in Novel Drug Delivery Systems // J. Nanotechnology Online, 2006. —www.azonano.com/Details.asp?ArticleID=1538