Self-titrating anticoagulant nanocomplexes that restore homeostatic regulation of the coagulation cascade.

Antithrombotic therapy is a critical portion of the treatment regime for a number of life-threatening conditions, including cardiovascular disease, stroke, and cancer; yet, proper clinical management of anticoagulation remains a challenge because existing agents increase the propensity for bleeding in patients. Here, we describe the development of a bioresponsive peptide-polysaccharide nanocomplex that utilizes a negative feedback mechanism to self-titrate the release of anticoagulant in response to varying levels of coagulation activity. This nanoscale self-titrating activatable therapeutic, or nanoSTAT, consists of a cationic thrombin-cleavable peptide and heparin, an anionic polysaccharide and widely used clinical anticoagulant. Under nonthrombotic conditions, nanoSTATs circulate inactively, neither releasing anticoagulant nor significantly prolonging bleeding time. However, in response to life-threatening pulmonary embolism, nanoSTATs locally release their drug payload and prevent thrombosis. This autonomous negative feedback regulator may improve antithrombotic therapy by increasing the therapeutic window and decreasing the bleeding risk of anticoagulants.

Point-of-care diagnostics for noncommunicable diseases using synthetic urinary biomarkers and paper microfluidics.

With noncommunicable diseases (NCDs) now constituting the majority of global mortality, there is a growing need for low-cost, noninvasive methods to diagnose and treat this class of diseases, especially in resource-limited settings. Molecular biomarkers combined with low-cost point-of-care assays constitute a potential solution for diagnosing NCDs, but the dearth of naturally occurring, predictive markers limits this approach. Here, we describe the design of exogenous agents that serve as synthetic biomarkers for NCDs by producing urinary signals that can be quantified by a companion paper test. These synthetic biomarkers are composed of nanoparticles conjugated to ligand-encoded reporters via protease-sensitive peptide substrates. Upon delivery, the nanoparticles passively target diseased sites, such as solid tumors or blood clots, where up-regulated proteases cleave the peptide substrates and release reporters that are cleared into urine. The reporters are engineered for detection by sandwich immunoassays, and we demonstrate their quantification directly from unmodified urine; furthermore, capture antibody specificity allows the probes to be multiplexed in vivo and quantified simultaneously by ELISA or paper lateral flow assay (LFA). We tailor synthetic biomarkers specific to colorectal cancer, a representative solid tumor, and thrombosis, a common cardiovascular disorder, and demonstrate urinary detection of these diseases in mouse models by paper diagnostic. Together, the LFA and injectable synthetic biomarkers, which could be tailored for multiple diseases, form a generalized diagnostic platform for NCDs that can be applied in almost any setting without expensive equipment or trained medical personnel.

Drug-induced amplification of nanoparticle targeting to tumors.

Nanomedicines have the potential to significantly impact cancer therapy by improving drug efficacy and decreasing off-target effects, yet our ability to efficiently home nanoparticles to disease sites remains limited. One frequently overlooked constraint of current active targeting schemes is the relative dearth of targetable antigens within tumors, which restricts the amount of cargo that can be delivered in a tumor-specific manner. To address this limitation, we exploit tumor-specific responses to drugs to construct a cooperative targeting system where a small molecule therapeutic modulates the disease microenvironment to amplify nanoparticle recruitment in vivo. We first administer a vascular disrupting agent, ombrabulin, which selectively affects tumors and leads to locally elevated presentation of the stress-related protein, p32. This increase in p32 levels provides more binding sites for circulating p32-targeted nanoparticles, enhancing their delivery of diagnostic or therapeutic cargos to tumors. We show that this cooperative targeting system recruits over five times higher doses of nanoparticles to tumors and decreases tumor burden when compared with non-cooperative controls. These results suggest that using nanomedicine in conjunction with drugs that enhance the presentation of target antigens in the tumor environment may be an effective strategy for improving the diagnosis and treatment of cancer.

Nanoparticles that sense thrombin activity as synthetic urinary biomarkers of thrombosis.

Thrombin is a serine protease and regulator of hemostasis that plays a critical role in the formation of obstructive blood clots, or thrombosis, that is a life-threatening condition associated with numerous diseases such as atherosclerosis and stroke. To detect thrombi in living animals, we design and conjugate thrombin-sensitive peptide substrates to the surface of nanoparticles. Following intravenous infusion, these "synthetic biomarkers" survey the host vasculature for coagulation and, in response to substrate cleavage by thrombin, release ligand-encoded reporters into the host urine. To detect the urinary reporters, we develop a companion 96-well immunoassay that utilizes antibodies to bind specifically to the ligands, thus capturing the reporters for quantification. Using a thromboplastin-induced mouse model of pulmonary embolism, we show that urinary biomarker levels differentiate between healthy and thrombotic states and correlate closely with the aggregate burden of clots formed in the lungs. Our results demonstrate that synthetic biomarkers can be engineered to sense vascular diseases remotely from the urine and may allow applications in point-of-care diagnostics.

Fast carbon nanotube detectors for micro gas chromatographs.

Highly sensitive and completely reversible chemiresistor detectors based on carbon nanotubes (CNTs) were fabricated for multi-component chemical analysis. CNT detectors were used in a series configuration with a gas chromatography column and exposed to a mixture of nine different compounds. It is shown that CNT detectors were able to show parts per billion (pbb) sensitivity responses to each individual component of the mixture and detect nine distinct chemical compounds in roughly 210 s when the detector operates in current stimulated desorption (CSD) mode. This is the first demonstration of an uncoated CNT detector to analyze multi-component chemical mixtures providing an alternative yet simple sensing approach for online air quality control and health monitoring applications.

Nanoparticles that communicate in vivo to amplify tumour targeting.

Nanomedicines have enormous potential to improve the precision of cancer therapy, yet our ability to efficiently home these materials to regions of disease in vivo remains very limited. Inspired by the ability of communication to improve targeting in biological systems, such as inflammatory-cell recruitment to sites of disease, we construct systems where synthetic biological and nanotechnological components communicate to amplify disease targeting in vivo. These systems are composed of 'signalling' modules (nanoparticles or engineered proteins) that target tumours and then locally activate the coagulation cascade to broadcast tumour location to clot-targeted 'receiving' nanoparticles in circulation that carry a diagnostic or therapeutic cargo, thereby amplifying their delivery. We show that communicating nanoparticle systems can be composed of multiple types of signalling and receiving modules, can transmit information through multiple molecular pathways in coagulation, can operate autonomously and can target over 40 times higher doses of chemotherapeutics to tumours than non-communicating controls.

Activating efficient phosphorescence from purely organic materials by crystal design.

Phosphorescence is among the many functional features that, in practice, divide pure organic compounds from organometallics and inorganics. Considered to be practically non-phosphorescent, purely organic compounds (metal-free) are very rarely explored as emitters in phosphor applications, despite the emerging demand in this field. To defy this paradigm, we describe novel design principles to create purely organic materials demonstrating phosphorescence that can be turned on by incorporating halogen bonding into their crystals. By designing chromophores to contain triplet-producing aromatic aldehydes and triplet-promoting bromine, crystal-state halogen bonding can be made to direct the heavy atom effect to produce surprisingly efficient solid-state phosphorescence. When this chromophore is diluted into the crystal of a bi-halogenated, non-carbonyl analogue, ambient phosphorescent quantum yields reach 55%. Here, using this design, a series of pure organic phosphors are colour-tuned to emit blue, green, yellow and orange. From this initial discovery, a directed heavy atom design principle is demonstrated that will allow for the development of bright and practical purely organic phosphors.

On the sensing mechanism in carbon nanotube chemiresistors.

There has been recent controversy whether the response seen in carbon nanotube (CNT) chemiresistors is associated with a change in the resistance of the individual nanotubes or changes in the resistance of the junctions. In this study, we carry out a network analysis to understand the relative contributions of the nanotubes and the junctions to the change in resistance of the nanotube network. We find that the dominant mode of detection in nanotube networks changes according to the conductance level (defect level) in the nanotubes. In networks with perfect nanotubes, changes in the junctions between adjacent nanotubes and junctions between the contacts and the CNTs can cause a detectable change in the resistance of the nanotube networks, while adsorption on the nanotubes has a smaller effect. In contrast, in networks with highly defective nanotubes, the changes in the resistance of the individual nanotubes cause a detectable change in the overall resistance of a chemiresistor network, while changes in the junctions have smaller effects. The combinational effect is also observed for the case in between. The results show that the sensing mechanism of a nanotube network can change according to the defect levels of the nanotubes, which may explain the apparently contradictory results in the literature.

Nonthermal current-stimulated desorption of gases from carbon nanotubes.

The desorption of gases from carbon nanotubes is usually a slow process that limits the nanotubes' utility as sensors or as memristors. Here, we demonstrate that flow in the nanotube above the Poole-Frenkel conduction threshold can stimulate adsorbates to desorb without heating the sensor substantially. The method is general: alcohols, aromatics, amines, and phosphonates were all found to desorb. We postulate that the process is analogous to electron-stimulated desorption, but with an internally conducted rather than externally applied source of electrons.

Biodegradable polyphosphoester micelles for gene delivery.

A new biodegradable polyphosphoester, poly[[(cholesteryl oxocarbonylamido ethyl) methyl bis(ethylene) ammonium iodide] ethyl phosphate] (PCEP) was synthesized and investigated for gene delivery. Carrying a positive charge in its backbone and a lipophilic cholesterol structure in the side chain, PCEP self-assembled into micelles in aqueous buffer at room temperature with an average size of 60-100 nm. It could bind and protect plasmid DNA from nuclease digestion. Cell proliferation assay indicated a lower cytotoxicity for PCEP than for poly-L-lysine and Lipofectamine. The IC50 determined by the WST-1 assay was 69.8, 51.6, and 12.1 microg/mL for PCEP, Lipofectamine, and poly-L-lysine, respectively. PCEP efficiently delivered DNA to several cell lines such as HEK293, Caco-2, and HeLa. The highest efficiency was achieved when PCEP/DNA complex was prepared in Opti-MEM with a +/- charge ratio of 1.5-2. The transfection efficiency did not change significantly when the complex was used 3 days after preparation. The addition of chloroquine to the formulation increased transfection efficiency 10- to 50-fold compared to the complex alone. In vivo studies showed a luciferase expression by PCEP/DNA complexes in muscle increasing with time during 3 months, although the expression level was lower than that by direct injection of naked DNA. In addition to biodegradability and lower toxicity, the PCEP micelle carrier offers structural versatility. The backbone charge density and the side chain lipophilicity are two parameters that can be varied through copolymerization and monomer variation to optimize the transfection efficiency.