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Nano-gels a Potential Carrier for Nanomedicine: A Review

Jagmeet Singh1*, Poonam Jaggi2 and Simranjeet Kaur3

1Department of Biotechnology, Lovely Professional University, Jalandhar, Punjab, India

2Department of Biotechnology, Amity University, Noida, New Delhi, India

3Department of Pharmacy, Chandigarh Group of Colleges, Landran, Mohali, Punjab, India

*Corresponding Author:
Jagmeet Singh
Department of Biotechnology
Lovely Professional University
Jalandhar, Punjab, India

Received Date: 08/11/2016; Accepted Date: 12/11/2016; Published Date: 16/11/2016

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Nanogels are being examined as medication conveyance specialists to target cancer cells/tissues because of easy accommodating characteristic and capability to smoothly encapsulate therapeutic agents of diverse nature by simple process. Nanogels are easily received by the target cancer cells, avoid gathering in non-target tissues thereby reduce the therapeutic amount and unsafe symptoms. However, we need essential clinical information identified with nanogels in order to permit rendering of the idea of nanogel for cancer treatment. This review concentrates on few of the latest advancement in nanogels as a delivery agent in the field of nanomedicine for cancer treatment.


Nano-medicine, Nanomachines, Nanobots, Drug delivery, Quantum dot


There has been sufficient research going on hydrogels that depicts the water cherishing 3D-polymer systems of nanogels that are equipped for expending a lot of physiological fluids or water, without bringing about any impact to the internal network structure. In past few years there is an increase interest in hydrogels circumscribed to nanoscale dimensions [1-4]. Nanogels can be modified to promote encapsulation of various diverse categories of bioactive compounds & various nanogel applications show their applicability as potential carrier for nanomedicine (1) Dispersion of nanogels have greater surface area that is very useful for in vivo nanogel applications. (2) Compounds having high or low molecular weights can be encapsulated in nanogels and increase therapeutic activity in biological environments is increased [5-8]. (3) For more effective and exact drug delivery of biopharmaceuticals in tissues/cells or crosswise over cell boundaries nanogels can be a promising alternate. (4) Nanogels have low buoyant density, high scattering solidness and sizable drug stacking limit in aqueous solutions. (5) Areas that are not effectively got to by hydrogels can be effortlessly surveyed by nanogels upon intravenous infusion [8-11].

Nanogels can be incorporated without drug as the drug can be effectively stacked into nanogels later when the nanogels are equilibrated and swollen in the biological fluid or water. Thus, the drug or therapeutic agent is not being exposed to any harsh conditions during synthesis. After organization into the body nanogels deliberately deliver the stacked therapeutic drug, can move inside the cells or tissues and discharge drug at the focused cell in vivo. The nanogels blend is being completed in fragile environment and in watery arrangement. Self-associating hydrophilic polymers grant encapsulation of bio-macromolecules and are helpful in synthesis of protein-loaded nanogels [12-17]. Chemical crosslinking is one method for manufacturing nanogel with bigger pore sizes. In order to avoid dissolution of the water loving polymer chains in aqueous solution crosslinks in the nanogels should be present. Labile bonds are introduced in hydrogels to prepare biodegradable hydrogels [18,19]. Various degradable bonds, such as phosphazene, amide, ester, anhydride, phosphate esters and carbonate are introduced either in polymeric chains or in cross-linkers that allows nanogel network degradation [20].

In spite of the hydrophilic nature, nanogels may offer limitation for the encapsulation of hydrophobic drugs; proper engineering of polymer matrix allows efficient encapsulation of less soluble anticancer drugs. Less soluble anticancer drugs can be introduced into nanogels to improving their stability and solubility that increases the chances of cellular uptake of the drug [21-23]. A study indicates two less dissolvable anticancer drug, 10-hydroxycamptothecin and paclitaxel (PTX) were stacked into nanogels by shell cross-linking of Pluronic F127 micelles. The nanogels has an unmistakable and smooth spherical shape that permit drug to scatter homogenously in the polymer network [24,25].

siRNA Loading on Nanogels

A small unit of interfering RNA (siRNA) is a double-stranded RNA molecule comprises of 21-23 nucleotides that repress synthesis of the proteins that are encoded by the messenger RNA (mRNA). The siRNA cause post-transcriptional gene silencing of particular protein by exasperating mRNA when it brought into cells. Nanogels are a promising interchange for any disease-causing gene and in addition for focusing on particular cell/tissue. As a gene directing tool siRNA has an inconceivable remedial ability in the areas of cancer treatment [26-29]. It's hard to stack siRNA in nanogel with high proficiency of encapsulation as it effectively gets spilled from the nanogel because of its water cherishing properties. siRNA is consolidated with cationic excipients to enhance the intractions between the molecule lattice and siRNA [30]. A Polyethyleneimine (PEI) nanogel is a potential siRNA delivery agent and the negative charge on siRNA permits it to form a solid electrostatic crosslinking with the postively charged polyethyleneimine. The meaningful poly-ionic complexes also safeguard siRNA from enzymatic degradation. Other negatively charged agents used for complexing are polyamines and di-oleyltrim-ethyl-ammoniumpropane [31-33].

Nanogels based on cationic dextran hydroxyethyl methacrylate (dex-HEMA) are potential siRNA transporters, as siRNA can be proficiently stacked into them are taken by tissues/cells in vitro and can transport immaculate/unique siRNA into the cells cytosol. The photopolymerization process is being utilized to stack siRNA into dextran nanogels with the assistance of UV prompted emulsion. Dextran nanogels were utilized as siRNA store from where siRNA can be discharged at the attractive time to increase the effect of gene silencing. It's been accounted for that with this the siRNA shot have been all the more productively come to the targeted cell [34-39]. Photochemical internalization is being utilized as a trigger to fortify endosomal leakage of siRNA with the assistance of amphiphilic photosensitizers. It was depicted that PEGylate cationic dex-HEMA nanogels with covalent connection of NHS-PEG to the dynamic amine group of the nanogels with a target to deliver siRNA in vivo. After PEGylation it was watched that dex-(HE)- MA-co-AEMA-co-TMAEMA nanogels kept up high stacking capability of siRNA. The dissemination of the negatively charged siRNA particles into the nanogels happens step by step and the siRNA was caught in the nanogels with the assistance of scat ionic charges [40-45].

Nanogel for Tumor Extracellular pH Targeting

Variation in pH between tumor tissue and healthy tissue can be used as an internal stimulus to trigger the release of drug. Due to the high rate of anaerobic and aerobic glycolysis in cancer cells, the pH of tumor tissue is lightly lower (pH 6.8) than that of healthy tissue (pH 7.4). Researchers utilized glycol chitosan (GCS) to manufacture a peculiar pH-sensible drug-carrying system that recognize the tumor pH [46-49]. The pH sensitivity was achived by propagating 3-diethylaminopropyl iso-thiocyanate (DEAP) to GCS. The pKb of DEAP ranges from 7.0 to 7.3 is similar to pH of tumor. The GCS-g-DEAP complex was used to manufacture pH senstive self-organized nanogel loaded with doxorubicin (DOX). The release of DOX was increased at pH 6.8 as compared to that at normal pH 7.4 signifies that the concentration of DOX is higher at cancer sites with an acidic pH 6.8. Such nanogel would therefore increase the therapeutic activity of the drug for treatment of in vivo cancers [50-56]. It was recommended that DOX loaded GCS-g-DEAP nanogels can be used for successfully targeting cancer-related acidic pH 6.8 and can also be used for triggering release at endosomal pH 6.0.

Tumoral acidic extracellular pH focusing was investigated for oridonin (ORI), a water revoking anticancer medication in Chinese conventional pharmaceutical. A pH-sensitive chitosan-g-poly(N-isopropylacrylamide) (CS-g-PNIPAm) based nanogel as a drug delivery system was created by self-assembly method. ORI-loaded nanogels have a pH-senstive fast drug release under lightly acidic conditions [57-63]. The drug release at pH 7.4 was slow, while it increased at lower pH of 6.0and6.5. ORI-stacked nanogels show a more cell cytotoxicity with respect to ORI solution at same pH. The anticancer cytotoxicity of ORI-stacked nanogels rather than HepG2 cells was impressively intensified at pH 6.5 contrasted with that at pH 7.4. Moreover, the IC50 value for the ORI-stacked nanogels was lesser at pH 6.5 compared to that at pH 7.4. Furthermore, the IC50 value for the ORI-loaded nanogels was lesser at pH 6.5 in comparison to pH 7.4 which indicates pH-dependent effect [64-69].

PEGylated Nanogels

PEGylation is the alteration of a particles surface by covalently entrapping, adsorbing or grafting polyethylene glycol (PEG). PEGylated nanoparticles stay in blood for longer time making the drug available for a long period of time. PEGylation of nanogels not only boost circulation time of nanogels but also delivers drug loaded on it into tumors following intravenous injection [70-73]. PEGylated nanogels can also be synthesized by chemically crosslinking poly(2-N,N-(diethylamino)ethyl methacrylate) (PEAMA) gel cores surrounded by PEG palisade layers. The PEGylated nanogels showed higher stability under very dilute and high salt conditions, in contrast to self-assembled nano-carriers. Moreover, the nanogels showed pH-senstive swelling/deswelling transitions across the pKa of the PEAMA gel core around pH 7.0. Such type of nanogels deswell under basic conditions and swells under acidic conditions.

Polysaccharide-PEG crossover nanogels (CHPOA-PEGSH) were cross-connected by both physical associations and covalent ester crosslinking by the synthetic response of a thiol-altered poly(ethylene glycol) (PEGSH) with acryloyl-changed cholesterol-bearing pullulan (CHPOA). The formulations were then injected intravenously in the mice to study blood clearance. CHP nanogels were get eliminated from the blood within time period of 6 hr, whereas the CHPOA-PEGSH nanogels had a longer circulation time of approximately 40-50% of the nanoparticles remained in circulation 6 h following injections and after 24 hr, 20-30% of the nanoparticles remained in the blood. The CHPOA-PEGSH nanoparticles half-life was about 15 fold greater than half-life of CHP nanogels demonstrating long circulation behavior of PEGylated nanogels [74-79].

Stimuli-responsive Nanogels

Nanogels displaying a stage move because of progress in outside conditions, for example pH, ionic quality, temperature or electric streams are known as ‘‘stimuli-responsive’’ nanogels. Nanogels swell due to solvent penetration into free spaces and this swelling behavior is influenced by external triggers, such as changes in environmental pH, ionic strength or temperature [80,81]. Nanogels show much faster responsiveness as compared to the conventional hydrogels. Multi-stimuli responsive nanogels are more powerful in focused treatment for cancer when contrasted with single responsive nanogels.

Kim et al. stacked doxorubicin in polypeptide-based nanogels with hydrophobic moieties in the cross-connected ionic centers. The nanogels had high drug stacking limit of 30 w/w% and were of extensively small size of 70 nm in diameter. The nanogels were observed to be enzymatically degradable prompting to quickened sedate discharge under mimicked lysosomal acidic pH. The doxorubicin stacked nanogels demonstrated enhanced antitumor movement contrasted with a free doxorubicin in an ovarian tumor xenograft mouse model conveying the utilization of such biodegradable nanogels as alluring transporters for delivery of chemotherapeutics. Doxorubicin was also loaded in chitin nanogels having pH sensitive controlled release. The drug release studies showed that doxorubicin release was more in acidic pH compared to neutral pH [82-85]. In the first hour 32% doxorubicin was released, which was similar in acidic and neutral pH. But after 24 h 60% of the drug was released under acidic condition, while just around 40% was discharged in the neutral environment. This distinction in discharge was ascribed to higher swelling of nanogel in acidic pH. Once more in another study doxorubicin was stacked in double boosts responsive empty nanogel spheres for pH subordinate intracellular delivery. The nanogels exhibited a pH-controlled drug release profile in an aqueous solution at 37 or 4 C. The cumulative drug release performed at pH 5.0 over a period of 3 h (50%) was much higher than that (20%) at pH 7.4. The delivery system showed guarantee in intracellular drug discharge for transport inside acidic endosomal or lysosomal compartments [86-88].

Intracellular Delivery of Nanogels

Intracellular drug delivery refers to the delivery of therapeutic agents to specific compartments or organelles within the cell. This targeted intracellular drug delivery brings about the higher bioavailability of a therapeutic at its site of activity, enhances the pharmacologic impact and diminishes the symptoms of the medication. Concentrates, for example intracellular distribution, cytotoxicity, cellular take-up hold guarantee for cancer chemotherapeutics [89-91]. Nanogels because of their small size offer intracellular distribution of therapeutic particles concerning cellular take-up by means of endocytosis and the enhanced permeation and retention (EPR) effect. In a recent study drug-loaded nanogels showed enhanced potency when compared to free drug after exposure to M21 cells. There was an important finding that the EC50 values of the cells exposed for 20 min with the nanogels were comparable with the cells exposed to the free drug for 72 h. Oh et al. arranged a pH-responsive self-sorted out nanogel stacked with DOX and assessed their cytotoxicity against A2780 cell line [92-94].

The better cell disguise of FA-CS-PF127 in the FR overexpressing KB cells was exhibited by CLSM and stream cytometry. Stream (flow) cytometry study was practiced to check the targeting proficiency the FA-altered nanogel (FA-CSPF127) and to examine the cell take-up in FR-positive KB cells. It was observed that FA-CS-PF127 nanogels move in KB cells proficiently and this FA focusing moiety was liable for the better internalization in the KB cells. Scientists have prepared paclitaxel (PTX) loaded nanogel with the help of shell cross-linking of Pluronic F127 micelles with polyethylenimine (PEI) (F127/PEI nanogel). The cytotoxicity of PTX-loaded F127/PEI nanogel was investigated using HEPG-2 cells [95-98]. The IC50 value data suggested that PTX-loaded nanogel displayed higher cytotoxicity compared with that of the free drug. The vacant folate altered F127/PEI nanogel did not demonstrate significant lethality in the entire concentration range correlated with the free PTX. The folate-changed PTX-stacked nanogel demonstrated a forebodingly unrivaled cytotoxicity as it has a much lower IC50 value. Folate-changed PTX-stacked nanogel was up taken proficiently into HEPG-2 cells than the non-altered F127/PEI nanogel because of the connection between the folate on the surface of nanogel and the folate receptors on the HEPG-2 cell surface. This cooperation guaranteed that more medications were reached into the tumor cells to give a superior anti-cancer effect [99,100].

Conclusion and Future of Nanomedicine

Nanogels are being examined as medication conveyance specialists to target cancer cells/tissues because of easy accommodating characteristic and capability to smoothly encapsulate therapeutic agents of diverse nature by simple process. Nanogels are easily received by the target cancer cells, avoid gathering in non-target tissues thereby reduce the therapeutic amount and unsafe symptoms. Although, last few years have endorsed intensive research in the nanogel manufacturing or synthesis, some factors are slowing the process of industrial production of the nanogels. These factors include inefficient translation of in vitro properties of nanogels to in vivo lethality concerns, immunogenicity, pharmacokinetics and viability of in vivo models, regulatory and bio-dissemination issues. There is a critical requirement for pertinent information from nanogels to allow interpretation of the nanogel into a live medical application for cancer treatment. As a drug delivery agent nanogels can improve the efficiency of cancer chemotherapy and benefit of the cancer patients.