We report that simple, synthetic organic polymer nanoparticles (NPs) can capture and clear a target peptide toxin in the bloodstream of living mice. The protein-size polymer nanoparticles, with a binding affinity and selectivity comparable to natural antibodies, were prepared by combining a functional monomer optimization strategy with molecular imprinting nanoparticle synthesis. As a result of binding and removal of melittin by NPs in vivo, mortality and peripheral toxic symptoms of melittin were significantly diminished. In vivo imaging of the polymer nanoparticles or "plastic antibodies" establishes the NPs accelerate clearance of the peptide from blood where they accumulate in the liver. Coupled with their biocompatibility and nontoxic characteristics, plastic antibodies offer potential for neutralizing a wide range of biomacromolecules in vivo.In nature, antibodies recognize target molecules by a combination of multiple weak electrostatic, hydrophobic and hydrogen bonding interactions between complementary threedimensional surfaces. To mimic these interactions, nanoparticles (NPs) with affinity for a target peptide or protein have been synthesized by optimizing the composition and ratio of functional groups that make up the NPs.1 , 2 However, the specificity and affinity of the random yhoshino@uci.edu; kjshea@uci.edu. Supporting Information Available: Experimental procedures and supporting data. This material is available free of charge via the Internet at http://pubs.acs.org. We have developed methods for synthesizing protein-size polymer particles with a binding affinity and selectivity comparable to natural antibodies by combining molecular imprinting nanoparticle synthesis with a functional monomer optimization strategy (Figure 1).9 The first stage of this process involves screening small libraries of NPs that span a compositional space chosen for its complementarity to the biological target. 2 The affinity of each NP to the biological target is evaluated and the composition of subsequent NP generations is adjusted to enhance specificity. At the final stage the optimized combination and ratio of functional monomers are polymerized in the presence of the imprinting biological target (peptide or epitope). 9 Following extensive dialysis, polymer NPs exhibit binding affinity, selectivity and particle size comparable to natural antibodies in vitro. NIH Public AccessAlthough molecular recognition by imprinted materials has been extensively studied in controlled settings, little is reported about their application in the bloodstream of living animals. 10 It is well known that the performance (affinity, specificity and function) of synthetic materials when introduced into a complex biological milieu can be profoundly compromised. Introduction of foreign substances including synthetic NPs into the bloodstream results in the immediate formation of a "corona" of proteins on the surface that can alter and/or suppress the intended function of the NP. 11 Further complications can arise fron an immunogenic re...

Summary We show that R-Ras, a small GTPase of the Ras family, is essential for the establishment of mature, functional blood vessels in tumors. The genetic disruption of R-Ras severely impaired the maturation processes of tumor vessels in mice. Conversely, the gain of function of R-Ras improved vessel structure and blood perfusion and blocked plasma leakage by enhanced endothelial barrier function and pericyte association with nascent blood vessels. Thus, R-Ras promotes normalization of the tumor vasculature. These findings identify R-Ras as a critical regulator of vessel integrity and function during tumor vascularization.

Designed polymer nanoparticles (NPs) capable of binding and neutralizing a biomacromolecular toxin are prepared. A library of copolymer NPs is synthesized from combinations of functional monomers. The binding capacity and affinity of the NPs are individually analyzed. NPs with optimized composition are capable of neutralizing the toxin even in a complex biological milieu. It is anticipated that this strategy will be a starting point for the design of synthetic alternatives to antibodies.

A major limitation in the pharmacological treatment of pulmonary arterial hypertension (PAH) is the lack of pulmonary vascular selectivity. Recent studies have identified a tissue-penetrating homing peptide, CARSKNKDC (CAR), which specifically homes to hypertensive pulmonary arteries but not to normal pulmonary vessels or other tissues. Some tissue-penetrating vascular homing peptides have a unique ability to facilitate transport of co-administered drugs into the targeted cells/tissues without requiring physical conjugation of the drug to the peptide (bystander effect). We tested the hypothesis that co-administered CAR would selectively enhance the pulmonary vascular effects of i.v. vasodilators in Sugen5416/hypoxia/normoxia-exposed PAH rats. Systemically administered CAR was predominantly detected in cells of remodeled pulmonary arteries. Intravenously co-administered CAR enhanced pulmonary, but not systemic, effects of the vasodilators, fasudil and imatinib, in PAH rats. CAR increased lung tissue imatinib concentration in isolated PAH lungs without increasing pulmonary vascular permeability. Sublingual CAR was also effective in selectively enhancing the pulmonary vasodilation by imatinib and sildenafil. Our results suggest a new paradigm in the treatment of PAH, using an i.v./sublingual tissue-penetrating homing peptide to selectively augment pulmonary vascular effects of nonselective drugs without the potentially problematic conjugation process. CAR may be particularly useful as an add-on therapy to selectively enhance the pulmonary vascular efficacy of any ongoing drug treatment in patients with PAH.

No abstract