The Study Of Drug-Loaded Surface Engineered Nanoparticles

Scientists have developed stealthy nanoparticles:in general, the surface of polymeric nanoparticles is modified with hydrophilic polymer material such e.g. polyethylene glycol (PEG), so that after entering the living body, nanoparticles avoid RES capture, enhance their in vivo circulation time and thereby effectively improve the nanoparticles concentration at tumor site. Moreover, carbohydrates, such as cyclodextrin, could be embedded on surface of nanoparticles to enhance the stability of nanoparticles by both hydrophilicity and steric repulsion. In order to increase the effects of nanoparticles on tumor cells, Scientists have developed some intelligent targeting polymeric nanoparticles, such as:stimuli responsive, tumor signaling molecules targeting and other nanoparticles. Stimuli responsive nanoparticles e.g. pH responsive nanoparticles cause structural and functional changes in polymeric nanoparticles in response to pH such as charge reversibility and structural destabilization. pH responsive nanoparticles are stable in physiological pH. But, as they penetrate tumor tissue in low pH, they may change their surface charges or shed their outer coating. Similarly, in signaling molecules targeting technologies, the nanoparticle surface is modified by some of the antibodies or ligands, these ligands can be tumor cell highly specific surface expression of certain molecules. They improve the nanoparticles and tumor cells interaction. Hence, improve the drug delivery efficiency. Meanwhile, the ligand and the polymeric nanoparticles are linked using PEG, in order to improve the in vivo residence time and long circulation of nanoparticles. However, the modified targeting ligands of the nanoparticles only show tumor tissue specific binding capacity in direct contact. When they are circulating in body, they do not show tumor tissue specific binding capacity. This is mainly because when nanoparticles surface ligands are circulating in the body; they can interact with blood protein or enzymes, which could block the effect of ligands in tumor cells and reduce the targeting role of nanoparticles. Furthermore, the role of PEG is weakened owing to interaction of surface ligands with blood proteins. Consequently, the long circulating characteristic of nanoparticles is decreased. These aforementioned disadvantages could be eliminated by fabricating multi-layered stimuli responsive nanoparticles. A protective layer on the nanoparticles could extend the circulation time in the body; surface of protective layer protects the nanoparticles from the body proteins and enzymes attack and maintains their long circulating characteristics. When nanoparticles arrive at tumor sites, protective layer stimulates due to tumor signals (such as, pH, temperature, and reducing environment),protective layer is removed and targeting ligands are exposed for binding to tumor cells. Therefore, ability of nanoparticles to deliver drug is improved.Based on above analysis, it is concluded that surface engineering of nanoparticles should be given special importance and many factors are needed to consider; nanoparticles should have long circulation characteristics as well as show affinity towards tumor cells and maintain their characteristics without disturbing each other independent role. Therefore, safe circulation of nanoparticles before reaching tumor site and precisely targeting to cancer cells is a key research topic in polymeric drug delivery systems.In summary, we developed different types of surface engineered polymeric nanoparticles. First, we formulated stealthy nanoparticles based on Cyclodextrin embedded on poly(e-caprolactone)-Poly(ethylene glycol)-Poly(ε-caprolactone) (PCL-PEG-PCL). Second, shed-able nanoparticles were synthesized by adding disulfide bond and folate was introduced on their surfaces. Later, we also added pH responsive characteristics in nanoparticles through charge-reversal Poly(ε-caprolactone)-Poly(ethylenimine) (PCL-PEI) copolymer. Overall, we have tried to produce different types of Surface engineered drug loaded nanoparticles for effective cancer therapy. Our research work specifically includes:(1)PCL-PEG-PCL was synthesized. It forms core-shell structure in aqueous solution. Antitumor drug, paclitaxel, was loaded in hydrophobic core of nanoparticles. Later, Cyclodextrin was conjugated with poly(acrylic acid) to synthesize poly(cyclodextrin acrylic acid) (PCDAA), and PCDAA was embedded on PCL-PEG-PCL nanoparticles. We focused on synergistic effect PEG and PCDAA. These nanoparticles possess long circulation characteristics due to presence of these two hydrophilic polymers on surfaces. Moreover, drug and other molecules can be encapsulated in inner cavities of cyclodextrin. The particle size of these nanoparticles was found to be less than 200nm. It is observed that the stability of these nanoparticles is due to hydrogen bonding between oxygen of PEG and carboxyl group of PCDAA. Drug loaded experiments described that these nanoparticles have very good encapsulation efficiency for Paclitaxel (PTX). Moreover, during in vitro drug release experiments, PTX is released very smoothly without any initial burst release of drug.In vitro cytotoxicity experiments show that these nanoparticles are not toxic for HepG2, but after loading PTX, They display the cytotoxicity of PTX.(2) Surface engineered nanoparticles (NPs) were fabricated from poly(ε-caprolactone)- Poly(ethylenimine)-Folic acid (PCL-PEI-FA) and poly(ε-caprolactone)-SS-Polyethylene glycol (PCL-SS-PEG) copolymers. Field emission Scanning Electron Microscope (FESEM) revealed the Core-shell structure of these NPs with about 225 nm size. It is assumed that Inner core of these NPs are composed of PCL containing Paclitaxel, while outer shell is adorned with PEG and folate introducing stealthy nature and specific targeting capability. Moreover, disulfide bonds of PCL-SS-PEG copolymers add reduction induced degradation characteristic in these NPs. Different properties of these NPs were determined:Inner hydrophobic core with maximum number of PEG chains have shown effective encapsulation of the greater amount of PTX. In vitro drug release studies confirmed the reduction induced shedding of NPs and exhibited drug release profile under reductive environment. Cell line experiments have exhibited the enhanced endocytosis and cytotoxicity of these NPs. Thus, these PCL-PEI-FA/PCL-SS-PEG Core-shell structure NPs could be better candidate for the tumor specific delivery of hydrophobic drug.(3)In last, we synthesized three kinds of amphiphilic copolymer i.e. PCL-SS-PEG, PCL-PEI and PCL-PEI-FA and self-assembled them into multifunctional nanoparticles. Morphological studies elucidated that these nanoparticles contain stable sandwich structure in aqueous solvent with hydrophobic PCL core, PEG and PEI hydrophilic shell. Detailed stimuli responsive capabilities of these NPs were carried out. Negative-to-positive charge reversible property and in response to pH change, were investigated by Zeta potential and Nuclear Magnetic Resonance (NMR).The structure cleavage, due to redox gradient, was studied by Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). These nanoparticles show negative-to-positive charge reversible property in response to pH change, degradation under reductive environment, and effective uptake in MCF-7 breast cancer cells. These multifunctional capabilities significantly improve the therapeutic efficacy of cancer treatment.