According to the National Cancer Institute, radiationtherapy or also simplified as radiotherapy is a growing method used in cancertreatment where it shrinks tumour and cancer cells using a high-energyradiation which include x-rays, gamma rays and charged particles. The therapyis divided into three which is external, internal and systemic radiation therapies.External-beam radiation therapy is done by using a machine called a linearaccelerator or LINAC where the radiation is incident towards the area outsideof the body where the cancer is located. On the other hand, internal radiationtherapy is done by delivering the radiation by means of a carrier inside thebody or on the body. Meanwhile, radioactive substance such as 131-iodine isbeing ingested or injected in systemic radiation therapy for treatment ofthyroid cancer. Radiotherapy for cancer treatment can be given with eithercurative intent or palliative intent. Curative treatment is intended by eradicatingthe tumour, preventing its recurrence or both and it is established eitheralone or in combination with other treatments such as surgery or chemotherapyor maybe both. Palliative treatment will be more focused on relieving the symptomsand minimising the pain in cancer patient rather than curing the cancer itself (National Cancer Institute, 2016).
Generally, radiation therapy works by killing or damaging tumourcells and it will take days to weeks for these cells to dies upon starting thetreatment and will continue to die for weeks or months after the treatment isover. There might be concern regarding the damaging effect of radiation onnormal healthy cells but in normal circumstances the cell will repairthemselves (Fronya and Moshe, 2016). The aims of developing a nano-system for drug delivery is toacquire a more specific drug targeting and delivery, increase efficacy, tominimise toxicity, providing higher biocompatibility and safety, and to developnew safe medicines in a short period of time.
For a nanoparticle to be a partof the drug delivery system, the nanoparticle formulation should bebiodegradable that it can easily release its content to the targeted site whileremaining stable throughout the journey. (De Jong and Borm, 2008). The efficiency ofnanoparticles in delivery drug to the target site relies on their size andsurface area. There are two ways of incorporating a drug to nanoparticles; byintegrating drugs in the particle matrix or by attaching drug molecules ontothe surface of the particle.
(Suri, Fenniri and Singh, 2007). These are done bydissolving, adsorbing, attaching, entrapping, and/or encapsulating the intendeddrugs into or onto a nano-matrix (Singh and W., 2009)Some examples of nanoparticles that have been developed formedical use are polymer, liposome, semiconductor and metal nanoparticles.Polymer of wide range have been used in this field due to their effectivenessin delivering drugs to target site which increases the drug therapeutic effectswhile keeping the side effects under control.
Liposomes is another type ofnanoparticles that have showed successful results in transporting drug due totheir capability to carry the drugs to the target site, prevent the degradationof drugs as well as reduce the side effects. Meanwhile, semiconductor andmetallic nanoparticles play a significant role in diagnosis and treatment forcancer. This is due to enhanced light scattering and absorption by theirsurface plasmon resonance (SPR) . Developing target specific nanoparticles has been a greatchallenge in establishing nano-system drug delivery. However, the challengesare amplified in the application of nanoparticles in cancer therapy sincetumour is known to be localised by metastasising to other organs. To overcomethis problem, technology of the nanoparticle which has specific characteristicswhich can be used as tools for local drug delivery and targeting is beneficial.Their small size enables them to penetrate the lipid bilayer, bind andstabilise proteins, and easier for them to be released from lysosome followingendocytosis.
(De Jong and Borm, 2008). Since it is required for thenano-system to be specific in targeting a target organ, tissues or organelles,there are a few ways for drug delivery targeting which include passive, activeand physical targeting (Yu et al.,2016).