A drug bringing system can be defined as the mechanism for the debut of drug and other curative agents into the organic structure for handling any disease. An ideal drug bringing system possesses two elements: ( 1 ) the ability to aim -to guarantee high efficiency and cut down the side effects, ( 2 ) controlled drug release & A ; ( 3 ) bar of side effects [ 8 ] . Using nanomaterials for drug bringing NDD ( nanoparticle drug bringing ) has the undermentioned advantages:
reduced drug toxicity
better incursion of the atoms
different bringing paths
minimizes the irritant reactions
improved bio-availability and increased circulation clip
controlled drug release and aiming
It is one of the “ Green Technology ” methods as the focal point is on minimising the jeopardy & A ; side effects and maximising the efficiency of any chemical ( drug ) of pick and replacing the bing merchandises with new nanoparticles that are friendly throughout their lifecycle [ 8 ] , [ 7 ] .
QUANTUM DOTS FOR NDDS:
NDDS means Nanoparticle Drug Delivery System. A system with high sensitiveness, big declaration, and low cost is needed for the care of drug bringing i.e. to look into the nanocarrier distribution, drug release and debasement inside the organic structure. Quantum Dots are extremely suited for such systems. [ 1 ] The of import features of Quantum points which make them suited for drug bringing systems are: little size, versatility of surface chemical science to integrate assorted drugs, alone optical belongingss for existent clip monitoring of drug conveyance and let go of both at systemic and cellular degrees. These Quantum Dots can be used as bearers by incorporating with many drugs and besides used as tickets for other drug bearers. [ 6 ]
WHY QUANTUM DOTS? ? ?
One of the of import grounds why Quantum Dots are preferred is that it can be used for the traceable drug bringing as it has the possible to clarify the pharmacokinetics ( what the organic structure does to the drug ) and pharmacodynamics ( what the drug does to the organic structure ) of drug when it is introduced into our organic structure [ 6 ] . Using QDs will be a combination of alone physical, chemical, and optical belongingss which helps to analyze the interactions of these nanocarriers with biological systems through real-time monitoring and ciphering the biodistribution of nanoparticle, drug release, intracellular consumption and debasement [ 5 ] . Comparing to the conventional imagination techniques like MRI and PET, the optical imagination utilizing Quantum Dots is extremely sensitive with high declaration and at really inexpensive cost which will automatically take to the decrease of clip involved in the development of new drug and many finds in the field [ 6 ] .
ADVANTAGES OF USING QDs
Optical imagination with high declaration, high sensitiveness, multiplexing, and low cost
Small size which leads to less sum of drug use and low drug toxicity
Versatile surface chemical science,
Improved bioavailability and bringing of drug in a controlled and sustained mode
Decreased incidence of side effects and better patient conformity
Comparing other conventional investigations, QDs are more immune which allows tracking cell processes for longer periods of clip and which will take to discovery of new molecular interactions
Quantum points have size dependent emanation which can be modified harmonizing to our demand ( from UV to IR scope )
Fluorescence is seen for longer clip when compared to conventional dyes.
The highly little size gives them great flexibleness by leting them utilizing different bringing paths eg. they can be injected as liquid mixtures, cloths, and polymer. [ 7 ]
PROPERTIES OF QDs
Some of the belongingss of Quantum Dots that are used to analyze nanocarrier behaviour in biological systems are: ( [ 2 ] , [ 5 ] , [ 7 ] )
Small size: size possibly around 2-10 nanometer in diameter that enables labeling of drug/carriers. Single or multi-component systems can be labeled for tracing and monitoring
Surface chemical science: compatibility with assorted drug bearers incorporating a broad scope of nanoparticle drug bearer system.
Emission profile: identifying quantum points by its crisp narrow emanation extremum allows coincident observation of multiple nanocarriers within a same system.
High brightness: sensing of QDs inside organic structure facilitates the tracing of nanocarriers in vivo.
High photostability: QDs are more immune to photobleaching that enables long term existent clip tracking.
QUANTUM DOTS AS NANOCARRIERS
Quantum Dots are considered as bearers and the curative drug molecules are straight linked to them to be delivered to the mark sites. Here it serves as both vehicle transporting the drug and following investigation used for the existent clip monitoring. In drug bringing, size of the Quantum Dots is considered as a really of import parametric quantity. The size of QDs varies from 2 – 10 nanometer, and it increases to 5 – 20 nanometer in diameter after drug encapsulation. It should be noted that QDs of size smaller than 5 nanometers are removed in the procedure of nephritic filtration and those atoms bigger is size have jobs in perforating through the tissues and many bigger atoms are wiped out before they could make their finish.
Another of import features of QDs to be considered for drug bringing is the ratio of surface-to-volume. If this ratio is high so multiple bearers can be linked on individual QDs without altering the mean diameter of the nanocarrier system. Thus the ratio of surface-to-volume should be high.
Fig.1 A Multifunctional Quantum Dot coated with Amphiphillic Polymer [ 6 ]
The above figure illustrates that QD acts as nucleus structural hydrophobic scaffold and the amphiphillic polymer is coated outside the nucleus. The drug molecules which are hydrophobic in nature are embedded between the nucleus and the polymer coating. And those hydrophilic curative molecules can be incorporated on the amphiphillic coating. Multiple beds of ligands can be linked in subsequent beds non straight linked to the QD nucleus but to the old beds of coating and is controlled by them. These nanocarriers besides protect the curative molecule or proteins used from the organic structure ‘s ain immune system defence mechanism by encapsulating them within themselves. [ 6 ]
Yamomoto et al did research on utilizing quantum points to handle shot in and reported that the nanocarriers “ QD – Capoten conjugates ” were capable of take downing blood force per unit area in rats. But it was non known whether the curative consequence of take downing force per unit area was due to the conjugate or the degage drug from the quantum points. [ 6 ] . Not merely drugs, other curative molecules like little interfering RNA, oligodeoxynucleotide and biomolecules e.g. antibodies, peptides can besides be incorporated into the nanocarriers. siRNA bringing utilizing quantum points was reported by Bhatia et Al. siRNA moleculeas were successfully delivered utilizing targeted nanocarriers because of the size similarity between QDs and siRNA. Whereas larger molecules like plasmid will necessitate many QDs for successful bringing. [ 6 ]
Mn-doped ZnS Qds encapsulated with glycopolypeptide were fabricated for the drug bringing. Word picture and in vitro surveies were done to turn out the low cytotoxicity of the nanocarriers and it was good attempt for the targeted drug bringing [ 4 ] .
QUANTUM DOTS AS TAGS FOR OTHER DRUG CARRIERS
Due to the alone belongingss of Quantum Dots, they are used as tickets to label other drug bearers and are used as traceable drug bringing. The high photostability helps in the existent clip trailing of the nanocarrier inside the organic structure. Therefore strong fluorescence signal indicates higher consumption of drug by the cells. The wavelength of the emitted signal depends on the size of the Quntum Dots used. Thus it is really specific to the QDs and thereby coincident nanocarriers can be used and the signals can be easy identified.
Chen et Al. reported about their work of siRNA bringing with QD conjugated with Lipofectamine. The consequences showed that fluorescence strength of QD is relative to the grade of hushing i.e. if lipoplex consumption is more than the fluorescence will be stronger. [ 6 ] Another work done by Zhang et Al. reported the synthesis of QD-chitosan conjugate nanobeads for the bringing of siRNA. It was successfully traced because of the junction with QDs. [ 6 ] Amphipol nanocpmplex were prepared for the existent clip imagination of siRNA by Lifeng et Al. it was delivered intracellularly and imaged in a existent clip form. [ 12 ]
SYNTHESIS AND CHARACTERIZATION
There are many ways of fixing Quantum Dots. Some of the celebrated procedure of manufacturing QDs are Lithography, Colloidal synthesis, Epitaxial methods, some chemical methods [ 2 ] , [ 10 ] .
By and large NDDS is prepared in the undermentioned stairss:
Nowadays many non-toxic semiconducting material QDs are used for the drug bringing. See for illustration ZnO. It is a non-toxic semiconducting material when compared to other Quantum Dots such as Cadmiums, CdTe. These QDs can be combined with biocompatible and biodegradable polymer to increase the stableness and non-immunogenicity of the nanocarriers. It besides shields the nanocarriers from the intervention of other interacting molecules indoors biological environment. Chitosan is a natural copolymer which on encapsulation enhances the quantum dots belongingss like solubility in H2O, metal chelation and easy processing and biocompatibility [ 3 ] .
Characterization surveies like TEM, UV-VIS, PL spectrometry, FTIR, Drug release response trial are done after the synthesis. TEM is used to happen out the size scope of the fancied QD. PL and PLE spectra give information about the emanation spectra. FTIR confirms the incorporation of the drug into the QD and Drug release response trial gives the sum of drug released and Tells about the type of drug bringing. [ 10 ] , [ 3 ] .
Quantum Dots will be the hereafter of drug bringing systems if the lone drawback has been eliminated. The lone disadvantage in utilizing Quantum Dots is their “ long term toxicity ” . This can be overcome by replacing the nucleus of the QD with biocompatible agents like gold or magnetic nanoparticles which offers a alone combination of therapy like magnetofection and photothermal intervention. Recent surveies show that quantum points to be safe on Primatess [ 9 ] . Quantum Dots will be a powerful tool to name and handle malignant neoplastic disease [ 11 ] . Thus quantum points will go the new epoch of drug bringing.