Self-assembled polymeric nanoparticles based on oleic acid-grafted chitosan oligosaccharide: biocompatibility, protein adsorption and cellular uptake

Carbohydrate anchored lipid nanoparticles

Nanotechnology has been a dynamic field for formulation scientists with multidisciplinary research being conducted worldwide. Advancements in development of functional nanosystems have led to evolution of breakthrough technologies. Lipidic nanosystems, in particular, are highly preferred owing to their non-immunogenic safety profiles along with a range of versatile intrinsic properties. Surface modification of lipid nanoparticles by anchoring carbohydrates to these systems is one such attractive drug delivery technology. Carbohydrates confer interesting properties to the nanosystems such as stealth, biostability, bioavailability, reduced toxicity due to decreased immunogenic response, targeting potential as well as ease of commercial availability. The carbohydrate anchored systems can be developed using methods such as adsorption, incorporation (nanoprecipitation or solvent displacement method), crosslinking and grafting. Current review provides a detailed overview of potential lipid based nanoparticulate systems with an emphasis on liposomes, solid lipid nanoparticles, nanostructures lipid carriers and micelles. Review further explores basics of surface modification, methods applied therein, advantages of carbohydrates as surface modifiers, their versatile applications, techniques for characterization of carbohydrate anchored systems and vital regulatory aspects concerned with these specialized systems.

Overcoming the protein corona in chitosan-based nanoparticles

Numerous properties of chitosan have led to its extensive use in the formulation of nanomaterials for drug delivery. However, the cationic surface of chitosan-based nanoparticles adsorbs proteins upon exposure to biological fluids, forming a phenomenon known as 'protein corona'. This causes several effects such as decreased bioavailability and limited in vivo clinical applications of chitosan nanoparticles. Understanding and overcoming the effects of protein adsorption on chitosan nanoparticles is key for drug delivery purposes. This review focuses on the strategies implemented to increase the stability of chitosan nanoparticles in the systemic circulation by averting the formation of protein corona and the limitations of PEGylation.

Biomedical and Pharmacological Uses of Fluorescein Isothiocyanate Chitosan-Based Nanocarriers

Chitosan-based nanocarriers (ChNCs) are considered suitable drug carriers due to their ability to encapsulate a variety of drugs and cross biological barriers to deliver the cargo to their target site. Fluorescein isothiocyanate-labeled chitosan-based NCs (FITC@ChNCs) are used extensively in biomedical and pharmacological applications. The main advantage of using FITC@ChNCs consists of the ability to track their fate both intra and extracellularly. This journey is strictly dependent on the physico-chemical properties of the carrier and the cell types under investigation. Other applications make use of fluorescent ChNCs in cell labeling for the detection of disorders in vivo and controlling of living cells in situ. This review describes the use of FITC@ChNCs in the various applications with a focus on understanding their usefulness in labeled drug-delivery systems.

Enhancing the performance of PEG-b-PCL-based nanocarriers for curcumin through its conjugation with lipophilic biomolecules

Curcumin is a natural substance extracted from Curcuma longa Linn with beneficial pharmaceutical properties such as anticancer activity against several cellular lines. However, it presents poor bioavailability due to its low solubility in aqueous media and chemical instability. In this research, curcumin was encapsulated in polymer micelles obtained by the self-assembly of a biodegradable poly (ethylene glycol)-block-poly(ɛ-caprolactone) copolymer conjugated with cholesterol or oleic acid. A hydroxyl-terminated poly (ethylene glycol)-block-poly(ɛ-caprolactone) was reacted with cholesteryl chloroformate or oleyl chloride to obtain conjugated copolymers. The resulting polymeric materials were characterised through proton nuclear magnetic resonance, gel permeation chromatography and differential scanning calorimetry, and their critical aggregation concentration was measured through fluorescence spectroscopy. Poly (ethylene glycol)-block-poly(ɛ-caprolactone) conjugated with cholesterol and oleic acid posed an improved capacity of encapsulating curcumin, resulting in the loading capacities of 8.8% and 15.2%, respectively. Cell viability studies confirmed that curcumin loaded in polymer micelles maintained its anticancer activity against MCF-7 human breast cancer cells but presented low cytotoxicity against mouse fibroblasts. Hence, these formulations have good potential for applications in drug delivery systems for breast cancer treatment.

Composite of Peptide-Supramolecular Polymer and Covalent Polymer Comprises a New Multifunctional, Bio-Inspired Soft Material

Peptide-based supramolecular hydrogels are utilized as functional materials in tissue engineering, axonal regeneration, and controlled drug delivery. The Arg-Gly-Asp (RGD) ligand based supramolecular gels have immense potential in this respect, as this tripeptide is known to promote cell adhesion. Although several RGD-based supramolecular hydrogels have been reported, most of them are devoid of adequate resilience and long-range stability for in vitro cell culture. In a quest to improve the mechanical properties of these tripeptide-based gels and their durability in cell culture media, the Fmoc-RGD hydrogelator is non-covalently functionalized with a biocompatible and biodegradable polymer, chitosan, resulting in a composite hydrogel with enhanced gelation rate, mechanical properties and cell media durability. Interestingly, both Fmoc-RGD and Fmoc-RGD/chitosan composite hydrogels exhibit thixotropic properties. The utilization of the Fmoc-RGD/chitosan composite hydrogel as a scaffold for 2D and 3D cell cultures is demonstrated. The composite hydrogel is found to have notable antibacterial activity, which stems from the inherent antibacterial properties of chitosan. Furthermore, the composite hydrogels are able to produce ultra-small, mono-dispersed, silver nanoparticles (AgNPs) arranged on the fiber axis. Therefore, the authors' approach harnesses the attributes of both the supramolecular-polymer (Fmoc-RGD) and the covalent-polymer (chitosan) component, resulting in a composite hydrogel with excellent potential.

Electrical Interconnects Fabricated From Biodegradable Conductive Polymer Composites

This study presents the development and characterization of biodegradable electrical interconnects for transient implantable medical devices. The interconnects comprised micropatterned biodegradable conductive polymer composites, which were developed using iron (Fe) microparticles as the conductive filler and polycaprolactone (PCL) as the insulating matrix. The electrical properties of the composites were investigated under various degradation conditions. Electrical percolation was observed at 17% iron volume fraction, but higher volume fractions exhibited more stable electrical resistivity throughout the time course of physiological degradation. The electrical resistivity of 40%vf Fe-PCL composites increased tenfold in an emulated packaged environment under degradation. Biodegradable electrical interconnects based on 40%vf Fe-PCL composites were successfully micropatterned in daisy chain structures, illustrating the process compatibility of Fe-PCL composites for interconnect applications. The electrical resistance of the packaged daisy chain structures exhibited a reasonable increase under degradation. An electrical lifetime of over 5 days was also achieved. System integration with a commercial humidity sensor and analytical calculations supporting other application scenarios confirmed the feasibility of micropatterned Fe-PCL interconnects for use in implantable electrical systems.

Micelles Structure Development as a Strategy to Improve Smart Cancer Therapy

Micelles as colloidal suspension have attracted considerable attention due to their potential use for both cancer diagnosis and therapy. These structures have proven their ability to deliver poorly water-soluble anticancer drugs, improve drug stability, and have good penetration and site-specificity, leading to enhance therapeutic efficacy. Micelles are composed of hydrophobic and hydrophilic components assembled into nanosized spherical, ellipsoid, cylindrical, or unilamellar structures. For their simple formation, they are widely studied, either by using opposite polymers attachment consisting of two or more block copolymers, or by using fatty acid molecules that can modify themselves in a rounded shape. Recently, hybrid and responsive stimuli nanomicelles are formed either by integration with metal nanoparticles such as silver, gold, iron oxide nanoparticles inside micelles or by a combination of lipids and polymers into single composite. Herein, through this special issue, an updated overview of micelles development and their application for cancer therapy will be discussed.

Fullerenol-Based Intracellular Delivery of Methotrexate: A Water-Soluble Nanoconjugate for Enhanced Cytotoxicity and Improved Pharmacokinetics

Derivatization of fullerenes to polyhydroxylated fullerenes, i.e., fullerenols (FLU), dramatically decreases their toxicity and has been reported to enhance the solubility as well as cellular permeability. In this paper, we report synthesis of FLU as nanocarrier and subsequent chemical conjugation of Methotrexate (MTX) to FLU with a serum-stable and intracellularly hydrolysable ester bond between FLU and MTX. The conjugate was characterized for physiochemical attributes, micromeritics, drug-loading, and drug-release and evaluated for cancer cell-toxicity, cellular-uptake, hemocompatibility, protein binding, and pharmacokinetics. The developed hemocompatible FL-MTX offered lower protein binding vis-à-vis naïve drug and substantially higher drug loading. The conjugate offered pH-dependent release of 38.20 ± 1.19% at systemic pH and 85.67 ± 3.39% at the cancer cell pH. FLU-MTX-treated cells showed significant reduction in IC₅₀ value vis-à-vis the cells treated with pure MTX. Analogously, the results from confocal scanning laser microscopy also confirmed the easy access of the dye-tagged FLU-MTX conjugate to the cell interiors. In pharmacokinetics, the AUC of MTX was enhanced by approx. 6.15 times and plasma half-life was enhanced by 2.45 times, after parenteral administration of single equivalent dose in rodents. FLU-MTX offered enhanced availability of drug to the biological system, meanwhile improved the cancer-cell cytotoxicity, sustained the effective plasma drug concentrations, and offered substantial compatibility to erythrocytes.

Inihibition of Glycolysis by Using a Micro/Nano-Lipid Bromopyruvic Chitosan Carrier as a Promising Tool to Improve Treatment of Hepatocellular Carcinoma

Glucose consumption in many types of cancer cells, in particular hepatocellular carcinoma (HCC), was followed completely by over-expression of type II hexokinase (HKII). This evidence has been used in modern pharmacotherapy to discover therapeutic target against glycolysis in cancer cells. Bromopyruvate (BrPA) exhibits antagonist property against HKII and can be used to inhibit glycolysis. However, the clinical application of BrPA is mostly combined with inhibition effect for healthy cells particularly erythrocytes. Our strategy is to encapsulate BrPA in a selected vehicle, without any leakage of BrPA out of vehicle in blood stream. This structure has been constructed from chitosan embedded into oleic acid layer and then coated by dual combination of folic acid (FA) and bovine serum albumin (BSA). With FA as specific ligand for cancer folate receptor and BSA that can be an easy binding for hepatocytes, they can raise the potential selection of carrier system.

Spontaneous Phase Transfer-Mediated Selective Removal of Heavy Metal Ions Using Biocompatible Oleic Acid

Here, we propose an environmentally benign removal technique for heavy metal ions based on selective and spontaneous transfer to oleic acid. The ions can be removed via (1) the selective and rapid complexation with the carboxylic end of oleic acid at an oleic acid/water interface, and (2) the diffusion of such complex into the oleic acid layer. A wide variety of heavy metal ions such as Cu²⁺, Pb²⁺, Zn²⁺, and Ni²⁺ can be selectively removed over K⁺ and Na⁺. For example, the concentration of Cu²⁺ is reduced to below 1.3 ppm within 24 h, which corresponds to the level of Cu²⁺ permitted by the Environmental Protection Agency. The addition of ethylenediamine ligand to the metal ion solutions is also shown to enhance the phase transfer. The removal efficiency is increased by up to 6 times when compared with that in the absence of the ligand and follows the order, Cu²⁺ (99%) > Pb²⁺ (96%) > Zn²⁺ (95%) > Ni²⁺ (65%). Moreover, the removal time can be shortened from 24 h to 1 h. The effect of an emulsion induced by a mechanical agitation on the removal of heavy metal ion is also studied.

Insights into the therapeutic potential of hypoxia-inducible factor-1α small interfering RNA in malignant melanoma delivered via folate-decorated cationic liposomes

Malignant melanoma (MM) represents the most dangerous form of skin cancer, and its incidence is expected to rise in the coming time. However, therapy for MM is limited by low topical drug concentration and multidrug resistance. This article aimed to develop folate-decorated cationic liposomes (fc-LPs) for hypoxia-inducible factor-1α (HIF-1α) small interfering (siRNA) delivery, and to evaluate the potential of such siRNA/liposome complexes in MM therapy. HIF-1α siRNA-loaded fc-LPs (siRNA-fc-LPs) were prepared by a film hydration method followed by siRNA incubation. Folate decoration of liposomes was achieved by incorporation of folate/oleic acid-diacylated oligochitosans. The resulting siRNA-fc-LPs were 95.3 nm in size with a ζ potential of 2.41 mV. The liposomal vectors exhibited excellent loading capacity and protective effect toward siRNA. The in vitro cell transfection efficiency was almost parallel to the commercially available Lipofectamine™ 2000. Moreover, the anti-melanoma activity of HIF-1α siRNA was significantly enhanced through fc-LPs. Western blot analysis and apoptosis test demonstrated that siRNA-fc-LPs substantially reduced the production of HIF-1α-associated protein and induced the apoptosis of hypoxia-tolerant melanoma cells. Our designed liposomal vectors might be applicable as siRNA delivery vehicle to systemically or topically treat MM.

Amphiphilic polysaccharide nanocarriers with antioxidant properties

The development of self-assembled nanocarriers for the encapsulation of hydrophobic antioxidants is of growing interest. Self-assembled amphiphilic chitosan conjugate nanocarriers that stabilize antioxidants were prepared based on the concept that both the nanocarrier and the antioxidant bear similar hydrophobic moieties able to establish hydrophobic interactions. This work describes the preparation and characterization of a system consisting of a palmitoyl chitosan conjugate and retinyl palmitate. Palmitic acid was coupled to chitosan using a carbodiimide-mediated coupling reaction, and two different palmitoyl chitosan conjugates were obtained by varying the coupling system. Palmitoyl chitosan conjugates self-assembled to form nanoparticles in aqueous medium varying in mean average diameter (Dh) between 200 and 437 nm. Retinyl palmitate–loaded nanoparticles were prepared by a solvent displacement method using dialysis, with loading efficiencies of 77.5% and 88.6%, loading contents of 12.6% and 14.6%, and Dh values of approximately 280 nm. The zeta potential (ζ) of all palmitoyl chitosan nanoparticle were above 25 mV, but ζ slightly increased in the retinyl palmitate–loaded nanoparticle. Antioxidant activity of loaded nanoparticles was confirmed using the 1,1-diphenyl-2-picryl-hydrazyl radical scavenging assay. The in vitro cytotoxicity of blank and loaded nanoparticles was determined using fibroblasts of human embryonic skin. All nanoparticles were not cytotoxic when they were tested with methylthiazol tetrazolium and lactate dehydrogenase tests. The obtained results suggest that the system has potential as a nanocarrier for dermal application. Additionally, the approach considered in this article can be expanded to other nanocarrier/antioxidant systems.

Self-assembled nanoparticles based on galactosylated O-carboxymethyl chitosan-graft-stearic acid conjugates for delivery of doxorubicin

A novel polymer, i.e. galactosylated O-carboxymethyl chitosan-graft-stearic acid (Gal-OCMC-g-SA) was synthesized for liver targeting delivery of doxorubicin. The chemical structure was characterized by FT-IR, (1)H NMR and elemental analysis. Gal-OCMC-g-SA could self-assemble into nanoparticles with diameter of 160 nm by probe sonication in aqueous medium and exhibited a low critical aggregation concentration of 0.047 mg/mL. The DOX-loaded Gal-OCMC-g-SA (Gal-OCMC-g-SA/DOX) self-assembled nanoparticles were almost spherical in shape with an average diameter of less than 200 nm and zeta potential of around -10 mV. In vitro release revealed that the Gal-OCMC-g-SA/DOX nanoparticles exhibited a sustained and pH-dependent drug release manner. Furthermore, the hemolysis test demonstrated the good safety of Gal-OCMC-g-SA in blood-contacting applications. These results indicated that Gal-OCMC-g-SA/DOX nanoparticles were highly potential to be applied in cancer therapy.

Characterization of protein and peptide binding to nanogels formed by differently charged chitosan derivatives

Chitosan (Chi) is a natural biodegradable cationic polymer with remarkable potency as a vehicle for drug or vaccine delivery. Chi possesses multiple groups, which can be used both for Chi derivatization and for particle formation. The aim of this work was to produce stable nanosized range Chi gels (nanogels, NGs) with different charge and to study the driving forces of complex formation between Chi NGs and proteins or peptides. Positively charged NGs of 150 nm in diameter were prepared from hexanoyl chitosan (HC) by the ionotropic gelation method while negatively charged NGs of 190 nm were obtained from succinoyl Chi (SC) by a Ca²⁺ coacervation approach. NGs were loaded with a panel of proteins or peptides with different weights and charges. We show that NGs preferentially formed complexes with oppositely charged molecules, especially peptides, as was demonstrated by gel-electrophoresis, confocal microscopy and HPLC. Complex formation was accompanied by a change in zeta-potential and decrease in size. We concluded that complex formation between Chi NGs and peptide/proteins is mediated mostly by electrostatic interactions.

The effect of nanoparticle uptake on cellular behavior: disrupting or enabling functions?

Nanoparticles (NPs) are materials with overall dimensions in the nanoscale range. They have unique physicochemical properties, and have emerged as important players in current research in modern medicine. In the last few decades, several types of NPs and microparticles have been synthesized and proposed for use as contrast agents for diagnostics and imaging and for drug delivery; for example, in cancer therapy. Yet specific targeting that will improve their delivery still represents an unsolved challenge. The mechanism by which NPs enter the cell has important implications not only for their fate but also for their impact on biological systems. Several papers in the literature discuss the potential risks related to NP exposure, and more recently the concept that even sublethal doses of NPs may elicit a cell response has been proposed. In this review, we intend to present an overall view of cell mechanisms that may be perturbed by cell-NP interaction. Published data, in fact, emphasize that NPs should no longer be viewed only as simple carriers for biomedical applications, but that they can also play an active role in mediating biological effects.