Nano-graphene oxide for cellular imaging and drug delivery

Two-dimensional graphene offers interesting electronic, thermal, and mechanical properties that are currently being explored for advanced electronics, membranes, and composites. Here we synthesize and explore the biological applications of nano-graphene oxide (NGO), i.e., single-layer graphene oxide sheets down to a few nanometers in lateral width. We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments. We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration. The NGO sheets are found to be photoluminescent in the visible and infrared regions. The intrinsic photoluminescence (PL) of NGO is used for live cell imaging in the near-infrared (NIR) with little background. We found that simple physisorption via π-stacking can be used for loading doxorubicin, a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro. Owing to its small size, intrinsic optical properties, large specific surface area, low cost, and useful non-covalent interactions with aromatic drug molecules, NGO is a promising new material for biological and medical applications. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. This article is published with open access at Springerlink.com     

TOF-SIMS characterization and imaging of controlled-release drug delivery systems

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for the analysis of multilayer drug beads that serve as controlled-release drug delivery systems. TOF-SIMS analysis of a cross section of each bead system allowed molecular chemical information to be gained from all of the layers simultaneously, in situ. The integrity of each of the layers was evaluated through imaging of specific ion species for the drug, excipient, and coating materials. The three beads in this study each showed a unique distribution of ingredients. Images of the parent molecular ion for each drug (theophylline, paracetamol, prednisolone) showed their distribution ranged from micrometer-sized particles in one bead cross section to almost homogeneous in another bead cross section. The chemical composition of each of the layers in the beads was evaluated through mass spectrometry; the ingredients did not always match the manufacturer's specification. In addition, many common drug bead ingredients were analyzed as pure substances, providing TOF-SIMS reference spectra of these materials for the first time.     

Preparation of amino-functionalized magnetite nanoclusters by ring-opening polymerization and application for targeted magnetic resonance imaging

Here we developed a ring-opening polymerization strategy for preparation of biocompatible and amino-functionalized superparamagnetic iron oxide nanoclusters (SPIONCs). The functionalized SPIONCs could be further applied for folate-receptor (FR)-targeted magnetic resonance imaging (MRI). The citrate-stabilized SPIONCs were synthesized by solvothermal reaction using biocompatible trisodium citrate (Na₃Cit) as the coordinating and stabilizing ligand and then the amino groups were covalently bonded to them through a ring-opening polymerization of epichlorohydrin and further treatment with ammonium hydroxide. The products were confirmed by XPS, FTIR, Zeta potential, and amino quantitative analysis. The amino-functionalized SPIONCs have good stability in aqueous solution and low cytotoxicity to cell lines. By in vitro MRI and quantitative element analysis, we demonstrated the FR-mediated delivery of the folic acid-conjugated SPIONCs (Fe₃O₄–FA) targeting FR-positive cell line such as human ovarian carcinoma cell. In conclusion, high magnetization, good stability, and effective FR-mediated uptake of the functionalized SPIONCs made them promising candidates for use as MRI contrast agents.     

Encapsulated microbubbles and echogenic liposomes for contrast ultrasound imaging and targeted drug delivery

Micron- to nanometer-sized ultrasound agents, like encapsulated microbubbles and echogenic liposomes, are being developed for diagnostic imaging and ultrasound mediated drug/gene delivery. This review provides an overview of the current state of the art of the mathematical models of the acoustic behavior of ultrasound contrast microbubbles. We also present a review of the in vitro experimental characterization of the acoustic properties of microbubble based contrast agents undertaken in our laboratory. The hierarchical two-pronged approach of modeling contrast agents we developed is demonstrated for a lipid coated (Sonazoid $^\mathrm{TM})$ and a polymer shelled (poly D-L-lactic acid) contrast microbubbles. The acoustic and drug release properties of the newly developed echogenic liposomes are discussed for their use as simultaneous imaging and drug/gene delivery agents. Although echogenicity is conclusively demonstrated in experiments, its physical mechanisms remain uncertain. Addressing questions raised here will accelerate further development and eventual clinical approval of these novel technologies.     

Growth and characterization of copper nanoclusters embedded in SiC matrix

Nanocrystalline copper clusters embedded in silicon carbide were made by island growth during sputter deposition. The distribution and morphology of metal clusters were observed by high-resolution transmission electron microscopy. To investigate chemical bonding at the copper-silicon carbide interface, we studied the electronic states of copper and silicon using X-ray photoelectron spectroscopy (XPS). It was found that the formation of copper silicide was suppressed in this system and that small shifts in binding energy were observed for different sizes of clusters, which was different from the chemical shift for copper silicide formation.     

Nanoparticles for cellular drug delivery: mechanisms and factors influencing delivery

Polymeric nanoparticles have demonstrated enormous potential as cellular drug delivery vehicles. Nanoparticles improve drug's stability as well as its availability and retention at the target intracellular site of action. Therapeutic efficacy of nanoparticles can be further enhanced by conjugating specific ligands to nanoparticle surface. Ligand conjugation can also be used to favorably modify the intracellular disposition of nanoparticles. A number of ligands are available for this purpose; use of a specific ligand depends on the target cell, the material used for nanoparticle formulation, and the chemistry available for ligand-nanoparticle conjugation. Cellular drug delivery using nanoparticles is also affected by clearance through the reticuloendothelial system. In this paper, we review the recent progress on our understanding of physicochemical factors that affect the cellular uptake of nanoparticles and the different cellular processes that could be exploited to enhance nanoparticle uptake into cells.     

Novel photothermal-responsive sandwich-structured mesoporous silica nanoparticles: synthesis,characterization, and application for controlled drug delivery

Novel thermal nanoparticles [hollow mesoporous silica nanospheres (HMSNs)–poly (N-isopropyl acrylamide-acrylic acid) PNIPAM-AA] were developed with Ag nanoparticles (AgNps) as the core, mesoporous silica nanoparticles as the layer, and thermally responsive polymers PNIPAM-AA as the shell. The AgNps had good photothermal effects, PNIPAM-AA was responsive to temperature, the combination of AgNps and PNIPAM-AA could be used as a photothermal-responsive switch for drug release, and HMSNs greatly increased the drug loading of the carrier. The samples were characterized by means of scanning electron microscopy, transmission electron microscopy, N₂ adsorption–desorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, and UV–Vis absorption spectra. The results showed that Ag@HMSN nanoparticles possessed a uniform diameter (330 nm), high specific surface area (822.45 m²/g), and mesoporous pore size (2.75 nm). Using ibuprofen (IBU) as a model drug, the release process was monitored under in vitro conditions to investigate its release characteristics at different temperatures. The results showed that the nanoparticles had a significant regulatory effect on IBU release.

Graphical abstract

     

A functionalized graphene oxide-iron oxide nanocomposite for magnetically targeted drug delivery, photothermal therapy, and magnetic resonance imaging

Two-dimensional graphene and its composite nanomaterials offer interesting physical/chemical properties and have been extensively explored in a wide range of fields in recent years. In this work, we synthesize a multi-functional superparamagnetic graphene oxide-iron oxide hybrid nanocomposite (GO-IONP), which is then functionalized by a biocompatible polyethylene glycol (PEG) polymer to acquire high stability in physiological solutions. A chemotherapy drug, doxorubicin (DOX), was loaded onto GO-IONP-PEG, forming a GO-IONP-PEG-DOX complex, which enables magnetically targeted drug delivery. GO-IONP-PEG also exhibits strong optical absorbance from the visible to the near-infrared (NIR) region, and can be utilized for localized photothermal ablation of cancer cells guided by the magnetic field. Moreover, for the first time, in vivo magnetic resonance (MR) imaging of tumor-bearing mice is also demonstrated using GO-IONP-PEG as the T ₂ contrast agent. Our work suggests the promise of using multifunctional GO-based nanocomposites for applications in cancer theranostics.      

Development and physico-mechanical characterization of carrageenan and poloxamer-based lyophilized matrix as a potential buccal drug delivery system

Context and objectives: The buccal mucosa presents a unique surface for non-invasive drug delivery and also avoids first-pass metabolism. The objective of this study was the formulation development of polymeric mucoadhesive lyophilized wafers as a matrix for potential buccal drug delivery.

Materials and methods: Differential scanning calorimetry (DSC) was used to develop an optimum freeze-cycle, incorporating an annealing step. The wafers were prepared by lyophilization of gels containing three polymers, κ-carrageenan (CAR 911), poloxamer (P407) and polyethylene glycol 600 (PEG 600). The formulations were characterized using texture analysis (for mechanical and mucoadhesion properties), hydration studies, thermogravimetric analysis (TGA), DSC, X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM).

Results and discussion: DSC showed the eutectic temperature (12.8?°C) of the system where the liquid solution and pure solids both existed at a fixed pressure which helped determine the freeze-annealing cycle at 55?°C for 7?h. Mechanical resistance to compression, hydration and mucoadhesion studies showed that optimized wafers were obtained from aqueous gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600. TGA showed residual water of approximately 1% and SEM showed a porous polymeric network that made ease of hydration possible.

Conclusions: Lyophilized wafers by freeze-drying gels containing 2% w/w CAR 911, 4% w/w P407 and 4.4% w/w PEG 600 with optimum physico-mechanical properties has been achieved.     

Acid-degradable gadolinium-based nanoscale coordination polymer: A potential platform for targeted drug delivery and potential magnetic resonance imaging

Nano Research - During conventional chemotherapy for cancer, nonspecific drug distribution, which causes serious side effects in normal tissues, is a serious limitation. Thus, it is desirable to...     

Synthesis of a biocompatible gelatin functionalized graphene nanosheets and its application for drug delivery

A simple and environmentally friendly synthetic route for the preparation of gelatin functionalized graphene nanosheets (gelatin-GNS) was reported by using exfoliated graphene oxide as a precursor, in which gelatin acted as not only a reducing reagent but also a functionalization reagent to guarantee good dispersibility and stability of the GNS in distilled water and various physiological solutions. The obtained biocompatible gelatin-GNS attaching methotrexate (MTX) via strong π-π stacking interaction, exhibited a high drug loading capacity of MTX and excellent ability for controlled drug release. The pH-dependent release behavior of MTX from MTX@gelatin-GNS showed that the release amount under acid conditions is much higher than that under neutral conditions, which experienced a gelatin-mediated sustained release process. From the cytotoxicity assay, we can see that the MTX@gelatin-GNS showed remarkable toxicity while the gelatin-GNS showed nontoxic at appropriate concentration, both of them might be taken up by A549 cells through a nonspecific endocytosis process. The prepared nanohybrids system offers a novel formulation that combines the unique properties of a biodegradable material, gelatin, and graphene for biomedical applications. Therefore, the gelatin-GNS with good stability and biocompatibility can be selected as an ideal drug carrier to be applied in biomedicine studies.     

Synthesis and characterization of thiolated carboxymethyl chitosan-graft-cyclodextrin nanoparticles as a drug delivery vehicle for albendazole

A new strategy for the synthesis of thiolated carboxymethyl chitosan-g-cyclodextrin nanoparticles by an ionic-gelation method is presented. The synthetic approach was based on the utilization of 1,6-hexamethylene diisocyanate during cyclodextrin grafting onto carboxymethyl chitosan. The use of the 1,6-hexamethylene diisocyanate resulted in reactions between cyclodextrin and active sites at the C₆-position of chitosan, and preserved amino groups of chitosan for subsequent reactions with thioglycolic acid, as the thiolating agent, and tripolyphosphate, as the gelling counterion. Various methods such as scanning electron microscopy, rheology and in vitro release studies were employed to exhibit significant features of the nanoparticles for mucosal albendazole delivery applications. It was found that the thiolated carboxymethyl chitosan-g-cyclodextrin nanoparticles prepared using an aqueous solution containing 1 wt% of tripolyphosphate and having 115.65 (μmol/g polymer) of grafted thiol groups show both the highest mucoadhesive properties and the highest albendazole entrapment efficiency. The latter was confirmed theoretically by calculating the enthalpy of mixing of albendazole in the above thiolated chitosan polymer.     

Beclomethasone-loaded lipidic nanocarriers for pulmonary drug delivery: preparation, characterization and in vitro drug release

The purpose of this research paper was the development of lipid nanoparticles (LN) formulation suitable for beclomethasone dipropionate (BDP) administration via the pulmonary route. Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were prepared by high-shear homogenization method; the effects of process and formulation parameters on nanoparticles characteristics were investigated. LN were characterized in terms of morphology, size, encapsulation efficiency, in vitro drug release and aerosol aerodynamic properties. Nano-sized BDP-loaded LN with high entrapment efficiency values reaching 99% were successfully obtained. Application of in vitro drug release data to the Higuchi kinetic equation indicated a diffusion-controlled release from the lipidic matrix. Aerosolisation and subsequent cascade impaction measurements proved that SLN and NLC were efficiently nebulized yielding aerosols of a suitable particle size for BDP deep lung delivery. Results demonstrate that LN are promising nebulized carriers for BDP opening the way for lipophilic drug-targeting strategies by nebulization.     

Glibenclamide-loaded self-nanoemulsifying drug delivery system: development and characterization

Objective: To develop and characterize self-nanoemulsifying drug delivery system (SNEDDS) of the poorly water-soluble drug, glibenclamide (GBD). Methods: Solubility of GBD was determined in various vehicles. Phase diagrams were constructed to identify efficient self-emulsification region using oils, surfactants, and cosurfactants in aqueous environment. Formulations were assessed for drug content, spectroscopic clarity, emulsification time, contact angle, zeta potential, particle size, and dissolution studies. On the basis of similarity and dissimilarity of particle size distribution, formulations were further characterized using principal component analysis and agglomerative hierarchy cluster analysis. Results: Among the formulations prepared and evaluated, optimized formulation showed mean particle size between 15.65 and 32.70 nm after 24 hour postdilution in various media. Dilution volume had no significant effect on particle size. Transmission electron microscopy of these formulations confirmed the spherical shape of globules with no signs of coalescence of globules and precipitation of drug. The relevance of difference in t50% and percent dissolution efficiency were evaluated statistically by two-way ANOVA. Infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction studies indicated compatibility between drug, oil, and surfactants. Conclusions: The results of this study indicate that the self-nanoemulsifying drug delivery system of GBD, owing to nanosize, has potential to enhance its absorption and without interaction or incompatibility between the ingredients.     

Surface-modified superparamagnetic nanoparticles for drug delivery: preparation, characterization, and cytotoxicity studies

Superparamagnetic iron oxide nanoparticles have been used for many years as magnetic resonance imaging (MRI) contrast agents or in drug delivery applications. In this study, a novel approach to prepare magnetic polymeric nanoparticles with magnetic core and polymeric shell using inverse microemulsion polymerization process is reported. Poly(ethyleneglycol) (PEG)-modified superparamagnetic iron oxide nanoparticles with specific shape and size have been prepared inside the aqueous cores of AOT/n-Hexane reverse micelles and characterized by various physicochemical means such as transmission electron microscopy (TEM), infrared spectroscopy, atomic force microscopy (AFM), vibrating sample magnetometry (VSM), and ultraviolet/visible spectroscopy. The inverse microemulsion polymerization of a polymerizable derivative of PEG and a cross-linking agent resulted in a stable hydrophilic polymeric shell of the nanoparticles. The results taken together from TEM and AFM studies showed that the particles are spherical in shape with core-shell structure. The average size of the PEG-modified nanoparticles was found to be around 40-50 nm with narrow size distribution. The magnetic measurement studies revealed the superparamagnetic behavior of the nanoparticles with saturation magnetization values between 45-50 electromagnetic units per gram. The cytotoxicity profile of the nanoparticles on human dermal fibroblasts as measured by standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that the particles are nontoxic and may be useful for various in vivo and in vitro biomedical applications.     

Synthesis of amphiphilic polythiophene for cell imaging and monitoring the cellular distribution of a cisplatin anticancer drug

A new amphiphilic conjugated polythiophene derivative (PT-Boc) is synthesized via Suzuki coupling reaction. The amphiphilic characteristic makes it form nanoaggregates in water, in which hydrophobic moieties come together to form the inner core. The polymer shows good photostability and no toxicity to human lung epithelial (A549) cells even at a high concentration (100 μg mL(-1) ). It therefore meets the crucial requirement for cellular imaging and other biological applications. The anticancer drug cisplatin is used as a model, and is linked to polythiophene to obtain a conjugate 'PT-Pt' by coordinated interactions between cisplatin and the amine groups of the polythiophene side chain. The PT-Pt can be used for monitoring the cellular distribution of cisplatin by fluorescence microscopy. The amphiphilic polythiophene provides a platform for fluorescent imaging of drugs and biological molecules in living cells.     

Hollow manganese phosphate nanoparticles as smart multifunctional probes for cancer cell targeted magnetic resonance imaging and drug delivery

Multifunctional probes for simultaneous magnetic resonance imaging (MRI) and drug delivery have attracted considerable interest due to their promising potential applications in the early-stage diagnosis and therapy of the diseases. In this study, hollow manganese phosphate nanoparticles (HMP NPs) with an average diameter of 18 nm were synthesized and aminated through silanization, which enabled the covalent conjugation of biocompatible poly(ethylene glycol) (PEG) on their surfaces. The anti-tumor drug doxorubicin (DOX) could be loaded into the hollow cavities. Under physiological conditions (pH 7.4), the NPs showed low MRI T ₁ contrast (r ₁ = 1.19 L·mmol^?1·s^?1), whereas high T ₁ enhancement (r ₁ = 5.22 L·mmol^?1·s^?1) was achieved after dissolving them in endosome/lysosome mimetic conditions (pH 5.4). This is due to the fact that the NPs were easily eroded, which resulted in the release of Mn²⁺ at low pH. To use this interesting phenomenon for targeted DOX drug delivery, we conjugated the tumor-targeting ligand folic acid (FA) on HMP NPs and investigated their drug delivery capacity and cytotoxicity to cell lines expressing different amount of folate receptor (FR). KB cells showed more significant cellular uptake than HeLa cells and A549 cells, as confirmed by confocal laser scanning microscopy (CLSM), flow cytometry and cellular T ₁-weighted MRI. Furthermore, the drug-loaded HMP NPs exhibited greater cytotoxicity to KB cells. Our results suggest that functionalized HMP NPs can act as an effective multifunctional probe for selective diagnosis with MRI, as well as giving efficient targeted drug delivery.      

Nanocrystal-based drug delivery system of risperidone: lyophilization and characterization

Objective: In the present work nanocrystal-based formulation of risperidone (RIS) was proposed to overcome solubility issue of RIS, while lyophilization technique was used effectively, for conversion of RIS nanosuspension to solid state.

Significance: RIS nanosuspension was developed and stabilized with a combination of polycaprolactone and Pluronic^® F-68 as stabilizers. With focus on critical parameters like nature of cryoprotectants and effect of eutectic temperature on properties of nanosuspension, the suitability of lyophilization technique in improving the physical stability of prepared nanosuspension was also evaluated. Additionally, the developed nanocrystals were also assessed for their solid states properties.

Methods: Various process parameters affecting average particle size and polydispersity index (PDI), viz. drug to surfactant ratio, solvent to anti-solvent ratio, stirring speed, type of stabilizer were optimized. Assessment of lyophilization as a suitable solidification technique (for conversion to powder form) was done with selective cryoprotectants (trehalose dihydrate and sorbitol).

Results: The formulation was found to be stable at 4?°C for 3 months with size, PDI and zeta potential of 214?±?3.4?nm, 0.120, and –10.2?±?0.90?mV, respectively. Release profile of developed nanosuspension showed cumulative % release of ～90% in initial 10?h whereas the value for the unprocessed drug was ～11% in same time frame.

Conclusions: These findings suggest that developed formulation was able to enhance water solubility of the drug effectively and can be potentially used in the management of psychotic disorders.     

Cancer nanotheranostics: improving imaging and therapy by targeted delivery across biological barriers

Cancer nanotheranostics aims to combine imaging and therapy of cancer through use of nanotechnology. The ability to engineer nanomaterials to interact with cancer cells at the molecular level can significantly improve the effectiveness and specificity of therapy to cancers that are currently difficult to treat. In particular, metastatic cancers, drug-resistant cancers, and cancer stem cells impose the greatest therapeutic challenge for targeted therapy. Targeted therapy can be achieved with appropriately designed drug delivery vehicles such as nanoparticles, adult stem cells, or T cells in immunotherapy. In this article, we first review the different types of nanotheranostic particles and their use in imaging, followed by the biological barriers they must bypass to reach the target cancer cells, including the blood, liver, kidneys, spleen, and particularly the blood-brain barrier. We then review how nanotheranostics can be used to improve targeted delivery and treatment of cancer cells. Finally, we discuss development of nanoparticles to overcome current limitations in cancer therapy.     

Synthesis and characterization of stable fluorocarbon nanostructures as drug delivery vehicles for cytolytic peptides

The therapeutic potential of cytolytic peptides is plagued by nonspecificity and enzymatic degradation. We report the first stable incorporation of melittin (a 26 amino acid amphipathic peptide) into an outer lipid monolayer of perfluorocarbon nanoparticles. Melittin binds avidly to the nanoparticles (dissociation constant approximately 3.27 nM) and retains its pore-forming activity after contact-mediated delivery to model bilayer membrane (liposomes) thereby demonstrating the effectiveness of perfluorocarbon nanoparticles as unique nanocarriers for cytolytic peptides.