Yanbing Zhao

Dual temperature/pH-sensitive drug delivery of poly(N-isopropylacrylamide-co-acrylic acid) nanogels conjugated with doxorubicin for potential application in tumor hyperthermia therapy.

In this paper, a dual temperature/pH-sensitive poly(N-isopropylacrylamide-co-acrylic acid) nanogel (PNA) was prepared and utilized as a drug carrier. The anti-cancer drug doxorubicin (DOX) was covalent bound to PNA via an acid-labile hydrazone linkage. DOX-PNA conjugates had a pH-dependent LCST, which was 41°C and 43°C at pH 5.3 and 6.8 respectively, but higher than 50°C at pH 7.4. The nanogels which were hydrophilic below LCST and changed to hydrophobic state above LCST possessed dual pH/temperature dependent cellular uptake and cytotoxicity. With increasing temperature, the cellular uptake of DOX-PNA was almost no difference at pH 7.4, but enhanced about 43% at pH 6.8. So the cytotoxicity of DOX-PNA also increased in higher temperature and lower pH value. It was able to distinguish tumor extracellular pH from physiological pH under hyperthermia of 43°C, suggesting a great potential for anti-cancer therapy.

pH/temperature sensitive magnetic nanogels conjugated with Cy5.5-labled lactoferrin for MR and fluorescence imaging of glioma in rats

Glioma is the most common primary brain tumor and causes a disproportionate level of morbidity and mortality across a wide range of individuals. From previous clinical practices, definition of glioma margin is the key point for surgical resection. In order to outline the exact margin of glioma and provide a guide effect for the physicians both at pre-surgical planning stage and surgical resection stage, pH/temperature sensitive magnetic nanogels conjugated with Cy5.5-labled lactoferrin (Cy5.5-Lf-MPNA nanogels) were developed as a promising contrast agent. Due to its pH/te mperature sensitivity, Cy5.5-Lf-MPNA nanogels could change in its hydrophilic/hydrophobic properties and size at different pH and temperatures. Under physiological conditions (pH 7.4, 37 °C), Cy5.5-Lf-MPNA nanogels were hydrophilic and swollen, which could prolong the blood circulation time. In the acidic environment of tumor tissues (pH 6.8, 37 °C), Cy5.5-Lf-MPNA nanogels became hydrophobic and shrunken, which could be more easily accumulated in tumor tissue and internalized by tumor cells. In addition, lactoferrin, an effective targeting ligand for glioma, provides active tumor targeting ability. In vivo studies on rats bearing in situ glioma indicated that the MR/fluorescence imaging with high sensitivity and specificity could be acquired using Cy5.5-Lf-MPNA nanogels due to active targeting function of the Lf and enhancement of cellular uptake by tailoring the hydrophilic/hydrophobic properties of the nanogels. With good biocompatibility shown by cytotoxicity assay and histopathological analysis, Cy5.5-Lf-MPNA nanogels are hopeful to be developed as a specific and high-sensitive contrast agent for preoperative MRI and intraoperative fluorescence imaging of glioma.

The dual temperature/pH-sensitive multiphase behavior of poly(N-isopropylacrylamide-co-acrylic acid) microgels for potential application in in situ gelling system.

Poly(N-isopropylacrylamide-co-acrylic acid) microgels (PNA) may be an excellent formulation for in situ gelling system due to their high sensitivity and fast response rate. Four monodispersed PNA microgels with various contents of acrylic acid (AA) were synthesized by emulsion polymerization in this paper. Their hydrodynamic diameters decreased reversibly with both decreasing pH and increasing temperature. The dual temperature/pH-sensitivity was influenced by many factors such as AA content, cross-link density and ion strength. In addition, high concentration PNA dispersions underwent multiple phase transition according to different temperatures, pHs and concentrations, which were summarized in a 3D sol-gel phase diagram in this study. According to the sol-gel phase transition, 8% PNA-025 dispersion maintained a relatively low viscosity and favorable fluidity at pH 5.0 in the temperature range of 25-40°C, but it rapidly increased in viscosity at pH 7.4 and gelled at 37°C. This feature enabled the dual temperature/pH-sensitive microgels to overcome the troubles in syringing of temperature sensitive materials during the injection. Apart from this, PNA could form gel well in in vitro (e.g., medium and serum) and in in vivo with low cytotoxicity. Therefore, it is promising for PNA to be applied in the in situ gelling system.

Temperature-Sensitive Fluorescent Organic Nanoparticles with Aggregation-Induced Emission for Long-Term Cellular Tracing

Temperature-sensitive organic nanoparticles with AIE effect were assembled in water from tetraphenylethene-based poly(N-isopropylacrylamide) (TPE-PNIPAM), which was synthesized by ATRP using TPE derivative as initiator. The size and fluorescence of TPE-PNIPAM nanoparticles can be tuned by varying the temperature. These nanoparticles can be internalized readily by HeLa cells and can be used as long-term tracer in live cells to be retained for as long as seven passages.

Highly Compressed Assembly of Deformable Nanogels into Nanoscale Suprastructures and Their Application in Nanomedicine

Assembly of nanoparticles as interfacial stabilizers at oil-in-water (O/W) interfaces into microscopic suprastructures for stabilizing Pickering emulsions is an intriguing focus in the fields of chemical industry and material sciences. However, it is still a major challenge to assemble nanoscale suprastructures using nanoparticles as building blocks at O/W interfaces for fabricating nanoscale emulsion droplets with applicable potential in nanomedicine. Here, we show that it is possible to fabricate the nanodroplets by assembling highly deformable nanogels into the nanoscale suprastructures at spatially confined O/W interfaces. The compressed assembly of the nanogels induced the formation of the nanoscale suprastructures upon energy input at the nanoscale O/W interface. The hydrogen bonding interaction between the nanogels at the O/W interface are possibly responsible for the stabilization of the nanoscale suprastructures. The nanoscale suprastructures are further employed to stabilize the paclitaxel-loaded nanodroplets, which are found to provide sustained release of the drug, enhanced in vitro cytotoxicity, and prolonged in vivo blood circulation. Furthermore, the tissue distribution and antitumor efficacy studies show that the nanodroplets could induce a higher drug accumulation at the tumor site and enhance tumor growth inhibition when compared with the commercial product. This approach provides a novel universal strategy to fabricate nanoscale suprastructures for stabilizing nanodroplets with built-in payloads using deformable nanoparticles and displays a promising potential in nanomedicine.

The studies about doxorubicin-loaded p(N-isopropyl-acrylamide-co-butyl methylacrylate) temperature-sensitive nanogel dispersions on the application in TACE therapies for rabbit VX2 liver tumor.

Transarterial chemo-embolization (TACE), which combined embolization therapy and chemotherapy, has become the most widely used treatment for unresectable liver cancer. Blood-vessel-embolic materials play key role on TACE. In the present work, doxorubicin-loaded p(N-isopropylacrylamide-co-butyl methylacrylate) nanogels-iohexol dispersions (IBi-D) were reported firstly for TACE therapy to liver cancer. Using inverting-vial method, IBi-D dispersions showed three phases (swollen gel, flowable sol and shrunken gel) as temperature increased. Although Dox had little effect on the CGTs between flowable and shrunken gel, the rheological properties of IBi-D dispersions could greatly improved by Dox. A sustained Dox-release, which was necessary in TACE therapy, was found from IBi-D dispersions in the eluting medium of PBS buffers. The studies about renal artery embolization of normal rabbits indicated that IBi-D dispersions showed good properties in embolizing all kinds of renal arteries (including peripheral, small and large arteries) by controlling their injecting dosages. Angiography and medical evaluation indicated that TACE therapy of IBi-D dispersions has better efficacy on rabbit VX2 liver tumors than TAC treatment of free Dox and TAE treatment of IBi dispersions.

Preparation and characterization of PEG-modified polyurethane pressure-sensitive adhesives for transdermal drug delivery

Background: The purpose of this work was to develop novel pressure-sensitive adhesives (PSAs) for transdermal drug-delivery systems (TDDS) with proper adhesive properties, hydrophilicity, biocompatibility and high drug loading. Method: Polyethyleneglycol-modified polyurethane PSAs (PEG-PU-PSAs) were synthesized by prepolymerization method with PEG-modified co-polyether and hexamethylene diisocyanate. The effects of reaction temperature, catalyst, ratios of NCO/OH, co-polyether composition, and chain extender were investigated. Drug loading was studied by using thiamazole (hydrophilic drug), diclofenac sodium (slightly hydrophilic drug), and ibuprofen (lipophilic drug) as model drugs. In vitro drug-release kinetics obtained with Franz diffusion cell and dialysis membrane. Results: The results showed that when reaction temperature at 80°C, weight percentage of stannous octoate as catalyst at 0.05%, ratio of NCO/OH at 2.0–2.2, ratio of PEG/polypropylene glycol (PPG)/polytetramethylene ether glycol (PTMG) at 30/25–30/50–55, and weight percentage of glycol as chain extender at 4.5%, PEGPU-PSAs synthesized performed well on adhesive properties. Actually, PEG on the main chain of the PU could improve the hydrophilicity of PSAs, whereas PPG and PTMG could offer proper adhesive properties. Skin compatibility test on volunteers indicated that PEG-PU-PSAs would not cause any skin irritations. All the model drugs had excellent stabilizations in PEG-PU-PSAs. In vitro drug-release kinetics demonstrated that the drug release depended on drug-loading level and solubility of the drug. Conclusion: These experimental results indicated that PEG-PU-PSAs have good potential for applications in TDDS.

Hydrophilicity/Hydrophobicity Reversable and Redox-Sensitive Nanogels for Anticancer Drug Delivery

Long circulation in the blood, efficient cellular internalization, and intracellular drug release in the tumor cells are major challenges in the development of ideal anticancer drug delivery systems. In this paper, hydrophilicity/hydrophobicity reversable and redox-sensitive poly(oligo(ethylene glycol) methacrylates-ss-acrylic acid) (P(OEGMAs-ss-AA)) nanogels were constructed as drug carriers for cancer therapy. The nanogels underwent a pH-dependent hydrophilic/hydrophobic change. The nanogels were hydrophilic under physiological conditions (pH 7.4, 37 °C), resulting in fewer opsonization of proteins and less phagocytosis by macrophage RAW264.7 cells, while they were hydrophobic in the tumor tissues (pH 6.5, 37 °C), resulting in strong internalization by Bel7402 cells. The doxorubicin (DOX) release from DOX-loaded nanogels was increased in intracellular reductive and lysosome acidic environments. DOX-loaded nanogels exhibited higher cellular proliferation inhibition to GSH-OEt-pretreated Bel7402 cells at pH 6.5 than to unpretreated cells at pH 7.4. Further studies showed that the loaded DOX and nanogels were internalized into the cells together via both lipid raft/caveolae- and clathrin-mediated endocytic pathways. After internalization, the DOX-loaded nanogels were transported via the specific route in endo/lysosomal system. The loaded DOX was released from the nanogels with the introduction of intracellular GSH and entered the nucleus. This study indicated that the hydrophilicity/hydrophobicity reversable and redox-sensitive nanogels might be used as potential carriers for anticancer drugs, which provided a foundation for designing an effective drug delivery system for cancer therapy.

Doxorubicin-induced co-assembling nanomedicines with temperature-sensitive acidic polymer and their in-situ-forming hydrogels for intratumoral administration

Doxorubicin (DOX)-induced co-assembling nanomedicines (D-PNAx) with temperature-sensitive PNAx triblock polymers have been developed for regional chemotherapy against liver cancer via intratumoral administration in the present work. Owing to the formation of insoluble DOX carboxylate, D-PNAx nanomedicines showed high drug-loading and entrapment efficacy via a simple mixing of doxorubicin hydrochloride and PNAx polymers. The sustained releasing profile of D-PNA100 nanomedicines indicated that only 9.4% of DOX was released within 1day, and 60% was released during 10days. Based on DOX-induced co-assembling behavior and their temperature sensitive in-situ-forming hydrogels, D-PNA100 nanomedicines showed excellent antitumor activity against H22 tumor using intratumoral administration. In contrast to that by free DOX solution (1.13±0.04 times at 9days) and blank PNA100 (2.11±0.34 times), the tumor volume treated by D-PNA100 had been falling to only 0.77±0.13 times of original tumor volume throughout the experimental period. In vivo biodistribution of DOX indicated that D-PNA100 nanomedicines exhibited much stronger DOX retention in tumor tissues than free DOX solution via intratumoral injection. D-PNA100 nanomedicines were hopeful to be developed as new temperature sensitive in-situ-forming hydrogels via i.t. injection for regional chemotherapy.

Temperature-Sensitive poly( N -Isopropylacrylamide-Co-Butyl Methylacrylate) Nanogel as an Embolic Agent: Distribution, Durability of Vascular Occlusion, and Inflammatory Reactions in the Renal Artery of Rabbits

BACKGROUND AND PURPOSE: We have developed a new thermosensitive liquid embolic agent, PIB nanogel, that can be solidified at body temperature. We thus further investigated the distribution, durability of vascular occlusion, and inflammatory reactions of PIB in embolization of the renal artery of rabbits. MATERIALS AND METHODS: The bilateral renal arteries of 9 rabbits were first embolized with PIB at different injection rates. The distribution pattern of PIB was investigated by contact radiography and histology 1 hour after embolization. The right renal arteries of 20 rabbits were then embolized with PIB at the proper injection rate. Angiography and pathologic examination of the kidneys were performed at 1 week and 1, 2, and 3 months after embolization to evaluate the long-term outcomes. RESULTS: With the injection rate increasing, PIB could reach the more distal branch of the renal artery. The proper injection rate was chosen as 0.10 mL/s due to the homogeneous distribution of PIB from the main renal artery to the precapillary level at this rate. During a 3-month follow-up observation period, no angiographic recanalization was observed. Histologically, we found no disruption of the vessel wall or subintimal bleeding, no extravasation of PIB, and no evidence of neovascularization. Moreover, there was only a mild inflammatory response, manifested by few lymphocytic and monocellular infiltration, without foreign body granuloma formation. CONCLUSIONS: Embolization of the renal artery with PIB was easy and controllable, which could lead to a homogeneous and persistent occlusion without severe inflammatory changes. PIB might be a suitable material for intravascular embolization.