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Oncolytic adenovirus (Ad) holds great promise as a potential gene therapy for cancer. However, intravenously administered Ad may encounter difficulties due to unfavorable host responses, non-specific interactions, and the heterogeneity of the tumor cell population. As an approach to combine the advantages of oncolytic Ad and synthetic polymers and to address the associated difficulties, Ad was physically complexed with a pH-sensitive block copolymer, methoxy poly(ethylene glycol)- b -poly( l -histidine) (mPEG- b -pHis). The in vitro transduction efficiency at an acidic extracellular pH was remarkably enhanced in cancer cells when treated with the Ad expressing green fluorescent protein (GFP) coated with mPEG- b -pHis (c-dE1/GFP) as compared to that of naked Ad (n-dE1/GFP). Time-lapse total internal reflection fluorescence microscopic imaging revealed a significantly enhanced cellular uptake rate of c-dE1/GFP at acidic tumor pH when compared with that at neutral pH or naked cognate Ad (n-dE1/GFP). In addition, c-dE1/GFP remained relatively stable in human serum-containing media, and considerably reduced both the innate and adaptive immune response against Ad. Moreover, the therapeutic efficacy and survival benefit of mPEG- b -pHis-complexed oncolytic Ad (c-H5mT/Luc) by systemic treatment was significantly enhanced compared to that with naked oncolytic Ad (n-H5mT/Luc) in both coxsackie and adenovirus receptor-positive and -negative tumors. Whole-body bioluminescence imaging showed 7.3-fold higher luciferase expression at the tumor site and 23.0-fold less luciferase expression in liver tissue for c-H5mT/Luc relative to that for naked oncolytic Ad (n-H5mT/Luc). Considering the heterogeneity of tumor tissue, these results are important for guiding the development of more potent and specific treatment of devastating metastatic cancers using this viral system. Statement of significance Although adenoviral systems have shown considerable promise and undergone extensive evaluation attempts to specifically target Ad vectors to cancer cells have met limited success. This shortcoming is due to the strong immune response stimulated by Ad and the hepatotoxicity of the viral particles. To overcome restricted vector issues, we generated Ad/mPEG- b -pHis for tumor microenvironment-targeting hybrid vector systems, an oncolytic Ad coated with a pH-responsive polymer, mPEG- b -pHis. The Ad/mPEG- b -pHis exhibited pH-dependent transduction efficiency and cancer-cell killing effects. Moreover, systemic administration of oncolytic Ad/mPEG- b -pHis led to marked suppression of tumor growth and tumor-specific viral replication. Ad successfully avoided the innate and adaptive immune responses and liver accumulation with the help of mPEG- b -pHis on its surface.

A new magnetic resonance imaging (MRI) contrast bearing RGD peptide is reported. In this study, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles with various sizes were prepared. Particles sizes between 6 and 13 nm were tuned by varying the stirring rate. Remarkable negative contrast was observed because USPIO nanoparticles (13.1 ± 2.1 nm) generated high transversal relaxivity r2 (188 ± 3 m m−1 s−1) and saturation magnetization (94 emu g−1 Fe). The USPIO nanoparticles were coated with PDA [2-(pyridyldithio)-ethylamine; PDA nanoparticles] containing functional polymer, which can be readily synthesized by Michael addition. The PDA nanoparticles were conjugated with RGD peptide (RGD nanoparticles) for targeting the specific site. The target specificity and high relaxivity allowed RGD nanoparticles to differentiate the expression level of integrin receptor on several cell lines and tumors (MCF-7, A-549, HT-29 and HT-1080) by in vitro and in vivo MR imaging. Importantly, a remarkable negative contrast (−51.3 ± 6.7%) was observed for in vivo MR imaging of MCF-7 tumor. This result implies that the RGD nanoparticles that greatly enhance the MR imaging are highly sensitive for early stage tumor detection. Copyright © 2012 John Wiley & Sons, Ltd.

Poly(γ-benzyl l -glutamate)- block -poly( l -phenylalanine) was prepared via the ring opening polymerization of γ-benzyl l -glutamate N -carboxyanhydride and l -phenylalanine N -carboxyanhydride using n -butylamine·HCl as an initiator for the living polymerization. Polymerization was confirmed by 1 H-nuclear magnetic resonance spectroscopy and matrix assisted laser desorption ionization time of flight mass spectroscopy. After deprotection, the vesicular nanostructure of poly( l -glutamic acid)- block -poly( l -phenylalanine) particles was examined by transmission electron microscopy and dynamic light scattering. The pH-dependent properties of the nanoparticles were evaluated by means of ζ-potential and transmittance measurements. The results showed that the block copolypeptide could be prepared using simple techniques. Moreover, the easily prepared PGA–PPA block copolypeptide showed pH-dependent properties due to changes in the PGA ionization state as a function of pH; this characteristic could potentially be exploited for drug delivery applications.

The MPEG-PAU block coplymers were successfully synthesized and their chemical structures were well characterized by1H,13C NMR and FT-IR spectroscopies. The aqueous solution properties of the copolymers were evaluated by acid-base titration, fluorescence spectroscopy and dynamic light scattering. The block copolymers exhibited a pHdependent micellization-demicellization transition in aqueous solution. The fluorescence spectroscopy and DLS measurements indicate that the micellization-demicellization transition occurs at pH 6.0–6.6. The amphiphilic block copolymers are expected to find applications in biomedical field.

A series of novel pH- and temperature-sensitive multiblock poly(ester amino urethane)s were synthesized. The copolymers were characterized by 1H NMR, FT-IR and GPC. In the multiblock copolymers, the tertiary amino groups of the poly(amino urethane) segments act as pH-responsive moieties, while the PCL–PEG–PCL blocks act as biodegradable and temperature-sensitive segments. At a relatively high pH (7.0 or above), the multiblock copolymer aqueous solution showed a sol-to-gel-to-aggregation transition with increasing temperature. In contrast, at a lower pH (below 7.0), the polymer solution always existed as a sol state within the experimental temperature range. The gel window covers the physiological conditions. After subcutaneous injection of the 20 wt% multiblock copolymer solutions into mice, polymeric hydrogels were formed in situ in a short time. The in vitro release of an anticancer drug, paclitaxel, persisted over 1 month under physiological conditions.

Block copolymer micelles are generally formed via the self-assembly of amphiphilic block copolymers in an aqueous medium. The hydrophilic and hydrophobic blocks form shell and core micelles, respectively. The block copolymers of methoxy poly(ethylene glycol) (MPEG)-b-poly(2-diisopropylamino)ethyl methacrylate (PDPA) were synthesized via atom transfer radical polymerization, with the macroinitiator synthesized by the coupling of 2-bromoisobutyryl bromide with MPEG in the presence of a triethyl amine base catalyst. The atom transfer radical polymerization of 2-diisopropylamino)ethyl methacrylate was performed in conjunction with anN,N,N′,N′’,N′’-pentamethyl-diethylenetriamine/copper bromide catalyst system, in DMF, at 70°C. The pH induced micellization/demicellization was studied using fluorescence, with a pyrene probe. Furthermore, the pH dependent micellization was confirmed using the microviscosity method, with a dipyme fluorescence probe. The pH dependant micelle size distribution was studied using dynamic light scattering. The characterization of the synthesized polymers was established using gel permeation chromatography and from the1H-nuclear magnetic resonance spectroscopy.

In order to prepare well-defined pH-sensitive block copolymers with a narrow molecular weight distribution (MWD), we synthesized a pH-sensitive block copolymer via atom transfer radical polymerization (ATRP) of sulfamethazine methacrylate monomer (SM) and amphiphilic diblock copolymers by the ring-opening polymerization of d , l -lactide/ ɛ -caprolactone (LA/CL), and their sol–gel phase transition was investigated. SM, which is a derivative of sulfonamide, was used as a pH responsive moiety, while PCLA–PEG–PCLA was used as a biodegradable, as well as a temperature sensitive one, amphiphilic triblock copolymer. The pentablock copolymer, OSM–PCLA–PEG–PCLA–OSM, was synthesized using Br–PCLA–PEG–PCLA-Br as an ATRP macroinitiator. The number average molecular weights of SM were controlled by adjusting the monomer/initiator feed ratio. The macroinitiator was synthesized by the coupling of 2-bromoisobutyryl bromide with PCLA–PEG–PCLA in the presence of triethyl amine catalyst in dichloromethane. The resultant block copolymer shows a narrow polydispersity. The block copolymer solution shows a sol–gel transition in response to a slight pH change in the range of 7.2–8.0. Gel permeation chromatography (GPC) and NMR were used for the characterization of the polymers that were synthesized.

Although oncolytic adenoviruses (Ads) are an attractive option for cancer gene therapy, the intravenous administration of naked Ad still encounters unfavorable host responses, non-specific interactions, and heterogeneity in targeted cancer cells. To overcome these obstacles and achieve specific targeting of the tumor microenvironment, Ad was coated with the pH-sensitive block copolymer, methoxy poly(ethylene glycol)-b-poly(L-histidine-co-L-phenylalanine) (PEGbPHF). The physicochemical properties of the generated nanocomplex, Ad/PEGbPHF, were assessed. At pH 6.4, GFP-expressing Ad/PEGbPHF induced significantly higher GFP expression than naked Ad in both coxsackie and adenovirus receptor (CAR)-positive and -negative cells. To assess the therapeutic efficacy of the Ad/PEGbPHF complex platform, VEGF promoter-targeting transcriptional repressor zinc-finger protein-expressing oncolytic Ad (KOX) was used to form complexes. At pH 6.4, KOX/PEGbPHF significantly suppressed VEGF gene expression, cancer cell migration, vessel sprouting, and cancer cell killing effect compared to naked KOX or KOX/PEGbPHF at pH 7.4, demonstrating that KOX/PEGbPHF can overcome the lack of CAR that is frequently observed in tumor tissues. The antitumor activity of KOX/PEGbPHF systemically administered to a tumor xenograft model was significantly higher than that of naked KOX. Furthermore, KOX/PEGbPHF showed lower hepatic toxicity and did not induce an innate immune response against Ad. Altogether, these results demonstrate that pH sensitive polymer coated Ad complex significantly increase net positive charge upon exposure to hypoxic tumor microenvironment, allowing it to passive target to tumor site. It may offer superior potential for systemic therapy, due to its improved tumor selectivity, increased therapeutic efficacy, and lower toxicity compared to naked KOX.

A new magnetic resonance imaging (MRI) contrast bearing RGD peptide is reported. In this study, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles with various sizes were prepared. Particles sizes between 6 and 13 nm were tuned by varying the stirring rate. Remarkable negative contrast was observed because USPIO nanoparticles (13.1 ± 2.1 nm) generated high transversal relaxivity r₂ (188 ± 3 m m(-1) s(-1) ) and saturation magnetization (94 emu g(-1) Fe). The USPIO nanoparticles were coated with PDA [2-(pyridyldithio)-ethylamine; PDA nanoparticles] containing functional polymer, which can be readily synthesized by Michael addition. The PDA nanoparticles were conjugated with RGD peptide (RGD nanoparticles) for targeting the specific site. The target specificity and high relaxivity allowed RGD nanoparticles to differentiate the expression level of integrin receptor on several cell lines and tumors (MCF-7, A-549, HT-29 and HT-1080) by in vitro and in vivo MR imaging. Importantly, a remarkable negative contrast (-51.3 ± 6.7%) was observed for in vivo MR imaging of MCF-7 tumor. This result implies that the RGD nanoparticles that greatly enhance the MR imaging are highly sensitive for early stage tumor detection.

A colorless and non-fluorescent rhodamine derivative, rhodamine B hydrazide (RH), is applied to detect nitric oxide and form fluorescent rhodamine B (RB). The reaction mechanism of RH with NO is proposed in this study. The probe shows good stability over a broad pH range (pH>4). Furthermore, fluorescence intensity of RH displays an excellent linearity to the NO concentration and the detection limit is as low as 20 nM. A 1000-fold fluorescence turn-on from a dark background was observed. Moreover, the selectivity study indicated that the fluorescence intensity increasing in the presence of NO was significantly higher than those of other reactive oxygen/nitrogen species. In exogenously generated NO detection study, clear intracellular red fluorescence was observed in the presence of S-nitroso-N-acetyl-D,L-penicillamine (SNAP, a kind of NO releasing agent). In endogenously generated NO detection study, increasing incubation time of RH with lipopolysaccharied (LPS) pre-treated cells could obtain a highly fluorescent cell image. These cell imaging results demonstrated that RH can efficiently penetrate into Raw 264.7 cells and be used for detection of exogenously and endogenously generated nitric oxide.