## 5 Discussion  
Our research is a probable solution to deal with the problems currently prevalent with the nano-delivery formulations because we demonstrate the use of a reagent free click chemistry technique to make a formulation that gives the flexibility to design a multi-targeted ligand library for nanoparticles with a wide choice of biologically safe carriers on a need-to-need basis. Studies reported, and techniques developed to successfully perform click chemical reactions proved them to be anything but difficult, and that they can be accomplished briskly with high yield to produce non-toxic products. Some scientists  
Figure 7: (**a**) Apoptosis assay studies in MDA-MB-231 for the hypoxia targeting drug delivery system BSA-PTX-ATZ; (**b**) Apoptosis assay studies in MDA-MB-468 for the hypoxia targeting drug delivery system BSA-PTX-ATZ; (**c**) Apoptosis assay studies in MDA-MB-231 and MDA-MB-468 based on the concentration of BSA-PTX-ATZ. now say that click chemistry is a calculatedly logical approach for effective improvement of the new molecular delivery systems. This specific but easy method relies essentially on carbon-heteroatom bonds using spring-loaded reactants. The growing extent of application of these reactions in designing delivery systems is observed in most of the specializations of cutting-edge pharmaceutical sciences discipline from drug delivery strategies to materials science [35; 36]. Due to the simplicity of click chemistry, it has been gaining importance in drug discovery, drug delivery, and bioconjugation reactions [37]. The system synthesized in this research is this sort of simple chemical procedure. This gives us the flexibility to create drug delivery systems for a choice of ligands and carriers for numerous hydrophobic drugs from different classes no longer confined to the cancer treatment. The biosafety of the carrier systems accordingly evolved is the key achievement of these formulation systems [38; 39]. The nanoparticles formed are in the nanoscale with a low PDI indicating nanoparticles to be of identical size as the average size of the particle. This characteristic feature of the particles promotes the uptake of the formulation into the cancerous cells via a weak vasculature system by way of the EPR effect [40; 41]. The formulation is noted to be robust with a minimum drug loss over a period of time establishing a viably long shelf-life by way of this formulation approach. Further, this approach creates a novel drug delivery system that shows sustained release properties too. Mechanistically speaking, the molecule is intended for use to deliver the drug to the core of tumor. To this end, it has been equipped with a targeting ligand, acetazolamide that will target a receptor that is highly expressed in the core of the hypoxic solid tumor. Carbonic anhydrase (CA IX) receptor is expressed in most of the solid tumors. Essentially, it is seen to be overexpressed in the core of the solid tumors where there is a shortage of oxygen. Hypoxia is a physiological condition of lack of oxygen that leads to acidosis which induces CA IX on the tumor cell surface that can be easily targeted using a suitable inhibitor like acetazolamide [19; 29; 33; 34]. Moreover, the BSA used for designing this nanoparticle serves as a biomimetic protein that easily circulates in the blood without producing any immunogenic effects. The incorporation of the NIR dye adds a diagnostic advantage to our drug delivery system. Putting all of these elements together with the advantages mentioned earlier of the synthesis technique and the nanoparticle design, the drug will be delivered with high specificity to the core of the tumor to show its cytotoxicity.To confirm the efficacy of our approach, we can show from the results of the cytotoxic studies, the formulation is observed to have more effect in the MDA-MB-468 that extensively overexpresses CA IX receptor in hypoxic conditions compared to MDA-MB-231 which is known to be a more difficult-to-treat strain [42].