Abhishek Sahu

Graphene oxide mediated delivery of methylene blue for combined photodynamic and photothermal therapy.

Nano graphene oxide sheet (nanoGO) was non-covalently functionalized with Pluronic block copolymer and complexed with methylene blue, a hydrophilic and positively charged photosensitizer, via electrostatic interaction for combined photodynamic-photothermal therapy of cancer. Pluronic coating of nanoGO ensured its stability in biological fluids. NanoGO plays dual role of a photothermal material as well as a delivery agent for photosensitizer. The release of the photosensitizer from nanoGO surface was pH-dependent and an acidic condition increased the release rate considerably. This nanocomplex showed enhanced uptake by cancer cells than normal cells and in the absence of light it showed no major toxicity towards the cells. In contrast, when irradiated with selective NIR laser lights, it induced significant cell death. Intravenous injection of the complex into tumor bearing mice showed high tumor accumulation, and when the tumors were exposed to NIR lights, it caused total ablation of tumor tissue through the combined action of photodynamic and photothermal effects. This work shows the potential of nanoGO for synergistic combination phototherapy of tumor in vivo.

Photothermal cancer therapy and imaging based on gold nanorods.

Gold nanorods (GNRs), which strongly absorb near-infrared (NIR) light, have shown great potential in fields of biomedical application. These include photothermal therapy, molecular imaging, biosensing, and gene delivery, especially for the treatment of diseased tissues such as cancer. These biomedical applications of GNRs arise from their various useful properties; photothermal (nanoheater) properties, efficient large scale synthesis, easy functionalization, and colloidal stability. In addition, GNRs do not decompose and have an enhanced scattering signal and tunable longitudinal plasmon absorption which allow them to be used as a stable contrast agent. Therefore, GNRs are also promising theranostic agents, combining both tumor diagnosis and treatment. In this review, we discuss the recent progress of invitro and invivo explorations of the diagnostic and therapeutic applications of GNRs as a component of cancer therapy.

Prussian blue/serum albumin/indocyanine green as a multifunctional nanotheranostic agent for bimodal imaging guided laser mediated combinatorial phototherapy.

Developing novel nanotheranostic agent using only clinically approved materials is highly desirable and challenging. In this study, we combined three clinically approved materials, Prussian blue (PB), serum albumin (BSA), and indocyanine green (ICG), by a simple and biocompatible method to prepare a multifunctional theranostic PB-BSA-ICG nanoparticle. The multifunctional nanoparticle system could provide dual mode magnetic resonance (MR) and near infrared (NIR) fluorescence imaging as well as combined photothermal and photodynamic (PTT-PDT) therapy in response to a single NIR laser. This nanoparticle showed an excellent stability in physiological solutions and could suppress the photo-instability of ICG. In the absence of light, the nanoparticles showed no cytotoxicity, but significant cell death was induced through combined PTT-PDT effect after irradiation with NIR laser light. A high tumor accumulation and minimal nonspecific uptake by other major organs of PB-BSA-ICG nanoparticle were observed in vivo, analyzed by T1-weighted MR and NIR fluorescence bimodal imaging in tumor xenograft mice after intravenous injection. The nanoparticles efficiently suppressed the tumor growth through combinatorial phototherapy with no tumor recurrence upon a single NIR laser irradiation. These results demonstrated that PB-BSA-ICG is potentially an interesting nanotheranostic agent for imaging guided cancer therapy by overcoming the limitations of each technology and enhancing the therapeutic efficiency as well as reducing side effects.

The effect of ligand density on in vivo tumor targeting of nanographene oxide

Recently, the application of nanographene oxide (nGO) as a drug delivery system has significantly increased. But, the rational engineering of nGO surface to improve its in vivo targeting and biodistribution remains mostly unexplored. In this study, we have prepared folic acid conjugated Pluronic for non-covalent functionalization of nanographene oxide (nGO) sheets and active tumor targeting. To modulate the ligand density on the nGO surface, different ratios of folate conjugated Pluronic and unmodified Pluronic were combined and used for coating nGO sheets. The surface density of targeting ligand linearly increased as the relative amount of folate conjugated Pluronic was increased. The association of functionalized nGOs with folate receptor overexpressing human epithelial mouth carcinoma cells (KB cells) was evaluated by flow cytometry. Cellular uptake of nGO by KB cells increased steadily with the increase in ligand density. In contrast, the in vivo experiment in mouse xenograft model did not show the steady increase in tumor targeting by increasing ligand density. Upon intravenous administration into KB tumor-bearing mice, tumor accumulation of nGO did not show a significant targeting effect up to 25% of ligand coating density. However, a strong and similar tumor accumulation of nGO was observed for both 50% and 100% folate coatings. Thus, a significant difference in tumor accumulation of nGO was observed between the low folate density groups and high folate density groups, suggesting the existence of a critical ligand density for tumor targeting. The significant difference of tumor targeting of nGO depending on ligand density also resulted in the dramatic change in photothermal tumor ablation by the irradiation of NIR laser.

Nanographene oxide as a switch for CW/pulsed NIR laser triggered drug release from liposomes

The application of pulsed and continuous wave (CW) lasers in nanomedicine has increased significantly over the last decade. Near infrared (NIR) lasers can be used for the precise control of drug release at the target site in a non-invasive manner. In this study, we have prepared nanographene oxide (nGO, size ~40nm) integrated liposomes (size ~900nm). The nGOs were not simply adsorbed onto the liposome surface but was embedded inside the liposomes as characterized by cryo-TEM, selected area electron diffraction (SAED), and fluorescence quenching studies. The embedded nGOs could act as a molecular switch for NIR light controlled drug release from the liposomes. Calcein was encapsulated into the liposome as a model drug to evaluate the efficiency of light controlled release. An on-demand pulsatile drug release was achieved by irradiation of CW/pulsed NIR lasers into the nGO-liposome suspension. Triggering with a pulsed laser resulted in larger release of calcein with a minimal temperature increase (~2°C) of the liposome solution, compared to lower release rate and a significant temperature increase (~8°C) by a CW laser with the same light energy, suggesting two separate mechanisms and different potential applications depending on the laser type.

Improved near infrared-mediated hydrogel formation using diacrylated Pluronic F127-coated upconversion nanoparticles

In situ hydrogel synthesis based on photopolymerization has been recognized as a promising strategy that can be used for tissue augmentation. In this study, we developed an efficient in situ gelation method to prepare bulk hydrogels via near infrared (NIR)-mediated photopolymerization using acrylated polyethylene glycol and diacrylated Pluronic F127-coated upconversion nanoparticles (UCNPs). In our system, upon 980-nm laser irradiation, UCNPs transmit visible light, which triggers the activation of eosin Y to initiate polymerization. We found that the UCNPs coated with diacrylated Pluronic F127 can enhance the photopolymerization efficiency and thus enable the production of bulk hydrogel with requirement of a lower NIR light power compared to that required with the bare UCNPs. This photopolymerization approach will be beneficial to achieve in situ polymerization in vivo for various biomedical applications such as cell/drug delivery and construction of tissue augments.

Recent Progress in the Design of Hypoxia‐Specific Nano Drug Delivery Systems for Cancer Therapy

Hypoxia is a salient feature in many solid tumors and an important player in tumor growth and progression. Increasing evidence suggests hypoxia plays major roles in the angiogenesis, metastasis, and resistance toward conventional cancer therapy treatments such as chemotherapy, radiotherapy, and photodynamic therapy. However, the exact reason that makes hypoxia a problem is also an opportunity for the development of new therapeutic modalities. The low oxygen level and highly reductive environment provide great options for stimuli‐sensitive drug release in a highly target‐specific manner. The use of nanoparticle‐based systems for hypoxia‐selective drug delivery is a relatively new but rapidly progressing research area. This report summarizes the recent trends and advances in the development of new hypoxia‐specific nanomedicines. The background, the current progress, and what could be done in the future to achieve greater success in cancer therapy are discussed.

A novel alendronate functionalized nanoprobe for simple colorimetric detection of cancer-associated hypercalcemia

The calcium (Ca2+) ion concentration in the blood serum is tightly regulated, and any abnormalities in the level of serum calcium ions are associated with many potentially dangerous diseases. Thus, monitoring of the Ca2+ ion concentration in the blood serum is of fundamental importance. Gold nanoparticle (GNP)-based colorimetric biosensors have enormous potential in clinical diagnostic applications due to their simplicity, versatility, and unique optical properties. In this study, we have developed an alendronate functionalized gold nanoparticle (GNP-ALD) system for the measurement of Ca2+ ion concentration in biological samples. The GNP-ALD system showed higher sensitivity towards the Ca2+ ion compared to adenosine diphosphate (ADP) or adenosine triphosphate (ATP). The strong interaction between the Ca2+ ion and ALD at the GNP/solution interface resulted in significant aggregation of the ALD conjugated GNPs, and induced a color change of the solution from red to blue, which could be visually observed with the naked eye. The interaction between the Ca2+ ion and GNP-ALD was characterized by UV-visible spectroscopy, transmission electron microscopy (TEM) imaging, and dynamic light scattering (DLS) analysis. Under the optimized conditions, the lower limit of Ca2+ ion detection using this method was found to be 25 μM and a linear response range from 25 μM to 300 μM Ca2+ ions was obtained with excellent discrimination against other metal ions. The GNP-ALD nanoprobe could successfully determine the ionized Ca2+ concentration in various serum samples and the results were validated using a commercial calcium assay kit. Moreover, as a practical application, we demonstrated the utility of this nanoprobe for the detection of cancer-associated hypercalcemia in a mouse model.

Comparison of in vivo targeting ability between cRGD and collagen-targeting peptide conjugated nano-carriers for atherosclerosis

Abstract Atherosclerosis plaque is a major cause of cardiovascular diseases across the globe and a silent killer. There are no physical symptoms of the disease in its early stage and current diagnostic techniques cannot detect the small plaques effectively or safely. Plaques formed in blood vessels can cause serious clinical problems such as impaired blood flow or sudden death, regardless of their size. Thus, detecting early stage of plaques is especially more important to effectively reduce the risk of atherosclerosis. Nanoparticle based delivery systems are recognized as a promising option to fight against this disease, and various targeting ligands are typically used to improve their efficiency. So, the choice of appropriate targeting ligand is a crucial factor for optimal targeting efficiency. cRGD peptide and collagen IV targeting peptide, which binds with the &agr;v&bgr;3 integrin overexpressed in the neovasculature of the plaque and collagen type IV present in the plaque, respectively, are frequently used for the targeting of nanoparticles. However, at present no study has directly compared these two peptides. Therefore, in this study, we have prepared cRGD or collagen IV targeting (Col IV‐tg‐) peptide conjugated and iron oxide nanoparticle (IONP) loaded Pluronic based nano‐carriers for systemic comparison of their targeting ability towards in vivo atherosclerotic plaque in Apolipoprotein E deficient (Apo E−/−) mouse model. Nano‐carriers with similar size, surface charge, and IONP loading content but with different targeting ligands were analyzed through in vitro and in vivo experiments. Near infrared fluorescence imaging and magnetic resonance imaging techniques as well as Prussian blue staining were used to compare the accumulation of different ligand conjugated nano‐caariers in the aorta of atherosclerotic mice. Our results indicate that cRGD based targeting is more efficient than Col IV‐tg‐peptide in the early stage of atherosclerosis. Graphical abstract Figure. No Caption available.

Bioinspired Heparin Nanosponge Prepared by Photo-crosslinking for Controlled Release of Growth Factors

Growth factors have great therapeutic potential for various disease therapy and tissue engineering applications. However, their clinical efficacy is hampered by low bioavailability, rapid degradation in vivo and non-specific biodistribution. Nanoparticle based delivery systems are being evaluated to overcome these limitations. Herein, we have developed a thermosensitive heparin nanosponge (Hep-NS) by a one step photopolymerization reaction between diacrylated pluronic and thiolated heparin molecules. The amount of heparin in Hep-NS was precisely controlled by varying the heparin amount in the reaction feed. Hep-NS with varying amounts of heparin showed similar size and shape properties, though surface charge decreased with an increase in the amount of heparin conjugation. The anticoagulant activity of the Hep-NS decreased by 65% compared to free heparin, however the Hep-NS retained their growth factor binding ability. Four different growth factors, bFGF, VEGF, BMP-2, and HGF were successfully encapsulated into Hep-NS. In vitro studies showed sustained release of all the growth factors for almost 60 days and the rate of release was directly dependent on the amount of heparin in Hep-NS. The released growth factors retained their bioactivity as assessed by a cell proliferation assay. This heparin nanosponge is therefore a promising nanocarrier for the loading and controlled release of growth factors.