ω-Hydroxy isoprenoid bisphosphonates as linkable GGDPS inhibitors.

The enzyme geranylgeranyl diphosphate synthase (GGDPS) is a potential therapeutic target for multiple myeloma. Malignant plasma cells produce and secrete large amounts of monoclonal protein, and inhibition of GGDPS results in disruption of protein geranylgeranylation which in turn impairs intracellular protein trafficking. Our previous work has demonstrated that some isoprenoid triazole bisphosphonates are potent and selective inhibitors of GGDPS. To explore the possibility of selective delivery of such compounds to plasma cells, new analogues with an ω-hydroxy group have been synthesized and examined for their enzymatic and cellular activity. These studies demonstrate that incorporation of the ω-hydroxy group minimally impairs GGDPS inhibitory activity. Furthermore conjugation of one of the novel ω-hydroxy GGDPS inhibitors to hyaluronic acid resulted in enhanced cellular activity. These results will allow future studies to focus on the in vivo biodistribution of HA-conjugated GGDPS inhibitors.

Hyaluronic acid formulation of near infrared fluorophores optimizes surgical imaging in a prostate tumor xenograft.

The presence of positive surgical margins confers an increased risk of biochemical relapse and need for salvage therapy in men undergoing radical prostatectomy. Image-guided surgery using near-infrared (NIR) fluorescent contrast agents is a potential method to detect remaining cancerous tissue. The objective of this study was to evaluate three hyaluronic acid (HA) nanoparticle (NP) formulations loaded with NIR fluorophore for their ability to contrast-enhance prostate cancer. HA was modified by conjugation with the hydrophobic ligand, aminopropyl-1-pyrenebutanamide to drive nanoparticle self-assembly. Indocyanine green (ICG) was physicochemically entrapped in the HA-NP, termed NanoICG. Alternatively, Cy7.5 was directly conjugated to amphiphilic HA, termed NanoCy7.5. NanoCy7.5 was synthesized with two HA molecular weights to determine the HA size contribution to delivery to PC3 prostate tumor xenografts. Contrast-enhancement of the tumors and relative biodistribution were assessed by a series of fluorescence imaging, image-guided surgery with spectroscopy, and microscopic techniques. Intravenously administered NanoICG improved tumor signal-to-noise ratio (SNR) at 24 h over ICG by 2.9-fold. NanoCy7.5 with 10 kDa and 100 kDa HA improved tumor SNR by 6.6- and 3.1-fold over Cy7.5 alone, respectively. The PC3 xenograft was clearly identified with the image-guided system providing increased contrast enhancement compared to surrounding tissue for NanoICG and NanoCy7.5 with 10 kDa HA. NIR fluorescence microscopy showed that Cy7.5 in NPs with 10 kDa HA were distributed throughout the tumor, while NanoCy7.5 with 100 kDa HA or NanoICG delivered dye mainly to the edge of the tumor. CD31 staining suggested that PC3 tumors are poorly vascularized. These studies demonstrate the efficacy of a panel of HA-derived NPs in identifying prostate tumors in vivo, and suggest that by tuning the structural properties of these NPs, optimized delivery can be achieved to poorly vascularized tumors. STATEMENT OF SIGNIFICANCE: We have demonstrated the potential of a panel of near-infrared fluorescent (NIRF) nanoparticles (NPs) for image-guided surgery in a prostate cancer xenograft model. Image-guided surgery and imaging of organs ex vivo showed greater tumor signal and contrast when mice were administered NIRF dyes that were covalently conjugated to (NanoCy7.510k-PBA) or physicochemically entrapped in (NanoICGPBA) hyaluronic acid (HA) NPs, compared to free dyes. These results show the potential to use these NPs as tools to detect the margins of tumors and to differentiate healthy and tumor tissue intraoperatively. Moreover, this project provides insight into selecting optimal formulation strategies for poorly vascularized tumors.

Probing the self-assembly dynamics and internal structure of amphiphilic hyaluronic acid conjugates by fluorescence spectroscopy and molecular dynamics simulations.

Polymeric nanoparticles are increasingly used as biocompatible carriers for drugs and imaging agents. Understanding their self-assembly dynamics and morphology is of ultimate importance to develop nanoformulations with optimal characteristics. To achieve better performance, it is vital to account for cargo-carrier interactions at the molecular level. The self-assembly dynamics were studied and the internal structure of nanoparticles derived from a series of hydrophobically modified hyaluronic acid was revealed. Environment-sensitive ratiometric fluorescent probes provide valuable information about the nanoparticle's interior morphology, and molecular dynamics simulations complement the overall picture with insights into intramolecular and intermolecular interactions of the polymer, as well as its interactions with the small-molecule load. van der Waals and π-π interactions of the hydrophobic side fragments play a leading role in self-assembly and loading of hydrophobic small molecules. Aliphatic substituents form more extensive hydrophobic domains, while aromatic moieties allow more interaction of the loaded small molecules with the surrounding solvent.

Development of colloidally stable carbazole-based fluorescent nanoaggregates.

Fluorescent nanomaterials require high colloidal stability for effective use in imaging and sensing applications. We herein report the synthesis of carbazole-based organic fluorescent nanoaggregates, and demonstrate the superior colloidal stability of alkyl-substituted dye aggregates over their non-alkylated analogs. The role of alkyl chains in self-assembly and stability of such nanoaggregates is discussed based on both experimental and molecular dynamics simulation data, and spectral characteristics of the precursor dyes and their aggregates are described. The obtained results provide new insights on development of colloidally stable organic fluorescent nanomaterials with low polydispersity.

The role of hydrophobic modification on hyaluronic acid dynamics and self-assembly.

The advent of nanomedicine has rejuvenated the need for increased understanding of the fundamental physicochemical properties of polymeric amphiphiles. Hyaluronic acid (HA) is a hydrophilic polysaccharide that is frequently conjugated to hydrophobic moieties and then used to entrap dyes and therapeutics. Here, we develop computational models to examine the effects of the hydrophobic modification on supramolecular behavior among three systematically designed HA derivatives substituted with alkyl chains of increasing length. Our simulations coalesce with experimentally obtained results to demonstrate the dependence of supramolecular behavior on intramolecular forces. We show that the formation of clearly defined hydrophobic domains in samples of octadecylamine-modified HA compared to HA conjugates with shorter alkyl chains is a result of more favorable hydrophobic interactions. Trends in hydrodynamic radius and polydispersity are observed in experimental results that coalesce with theoretical calculations, suggesting that supramolecular properties are dependent on the physicochemical characteristics of individual polymer strands.

Multimodal Imaging Nanoparticles Derived from Hyaluronic Acid for Integrated Preoperative and Intraoperative Cancer Imaging.

Surgical resection remains the most promising treatment strategy for many types of cancer. Residual malignant tissue after surgery, a consequence in part due to positive margins, contributes to high mortality and disease recurrence. In this study, multimodal contrast agents for integrated preoperative magnetic resonance imaging (MRI) and intraoperative fluorescence image-guided surgery (FIGS) are developed. Self-assembled multimodal imaging nanoparticles (SAMINs) were developed as a mixed micelle formulation using amphiphilic HA polymers functionalized with either GdDTPA for T1 contrast-enhanced MRI or Cy7.5, a near infrared fluorophore. To evaluate the relationship between MR and fluorescence signal from SAMINs, we employed simulated surgical phantoms that are routinely used to evaluate the depth at which near infrared (NIR) imaging agents can be detected by FIGS. Finally, imaging agent efficacy was evaluated in a human breast tumor xenograft model in nude mice, which demonstrated contrast in both fluorescence and magnetic resonance imaging.

Near Infrared Fluorescent Nanoparticles Derived from Hyaluronic Acid Improve Tumor Contrast for Image-Guided Surgery.

Tumor tissue that remains undetected at the primary surgical site can cause tumor recurrence, repeat surgery, and treatment strategy alterations that impose a significant patient and healthcare burden. Intraoperative near infrared fluorescence (NIRF) imaging is one potential method to identify remaining tumor by visualization of NIR fluorophores that are preferentially localized to the tumor. This requires development of fluorophores that consistently identify tumor tissue in different patients and tumor types. In this study we examined a panel of NIRF contrast agents consisting of polymeric nanoparticle (NP) formulations derived from hyaluronic acid (HA), with either physically entrapped indocyanine green (ICG) or covalently conjugated Cy7.5. Using orthotopic human breast cancer MDA-MB-231 xenografts in nude mice we identified two lead formulations. One, NanoICGPBA, with physicochemically entrapped ICG, showed 2.3-fold greater tumor contrast than ICG alone at 24 h (p < 0.01), and another, NanoCy7.5100-H, with covalently conjugated Cy7.5, showed 74-fold greater tumor contrast than Cy7.5 alone at 24 h (p < 0.0001). These two lead formulations were then tested in immune competent BALB/c mice bearing orthotopic 4T1 breast cancer tumors. NanoICGPBA showed 2.2-fold greater contrast than ICG alone (p < 0.0001), and NanoCy7.5100-H showed 14.8-fold greater contrast than Cy7.5 alone (p < 0.0001). Furthermore, both NanoICGPBA and NanoCy7.5100-H provided strong tumor enhancement using image-guided surgery in mice bearing 4T1 tumors. These studies demonstrate the efficacy of a panel of HA-derived NPs in delineating tumors in vivo, and identifies promising formulations that can be used for future in vivo tumor removal efficacy studies.

High-Capacity and Rapid Removal of Refractory NOM Using Nanoscale Anion Exchange Resin.

As human health concerns over disinfection byproducts (DBP) in drinking water increase, so does the need to develop new materials that remove them rapidly and at high capacity. Ion exchange (IEX) is an effective method for the removal of natural organic matter (NOM), especially anion exchange resins (AERs) with quaternary ammonium functional groups. However, capacity is limited in existing commercial resin materials because adsorbates can only interact with the outermost surface area, which makes these products inefficient on a mass basis. We have synthesized a novel "NanoResin" exploiting the enhanced NOM removal of the quaternary ammonium resin while utilizing the vast surface area of SWCNTs, which act as scaffolding for the resin. Our nanomaterials show increased adsorption capacity compared to commercially available adsorbents, in a fraction of the time. This NanoResin requires only about 10 s to reach ion-exchange equilibrium. Comparatively, commercial AERs only achieved partial removal after more than 30 min. High capacity adsorption of a low molecular weight (MW) surrogate has been measured. NOM removal was demonstrated in solutions of both low and high specific UV absorbance (SUVA) composition with these nanomaterials. Additionally, the NanoResin showed enhanced removal of a NOM concentrate sample taken from Myrtle Beach, SC, demonstrating NanoResin is an effective method of removal for refractory NOM in a natural aqueous environment. Synthesis and characterization of the polymers and nanomaterials are presented below. Adsorption capacity, adsorption kinetics, and the regeneration and reusability of these new materials for NOM removal are described. The open matrix microstructure precludes any intraparticle diffusion of adsorbates; thus, these nanomaterials act as a "contact resin".