Amino Acid-Based Poly(ester urea)s as a Matrix for Extended Release of Entecavir.

The use of polymers as excipients for drug delivery has afforded stable formulations that reliably control the release of active pharmaceutical ingredients (APIs). While many materials are available and used, few polymers exhibit the numerous advantages, including amorphous characteristics, noninflammatory properties, and resorbable degradation products, like those of poly(ester urea)s (PEUs). Furthermore, stability issues that arise in various APIs can make formulation optimization difficult. Herein, a series of PEUs were synthesized that vary by the fraction of l-phenylalanine monomer incorporated into the copolymerization. The various PEUs and entecavir monohydrate were dry-mixed at different weight percentages (15, 30, and 50%). Filaments of the PEU formulations were extruded and analyzed quantitatively for drug loading and content uniformity by using µ-CT and UPLC analysis. Drug dissolution profiles from filament segments were monitored over a 4-week period and ultimately showed that the controlled release of entecavir was influenced by the incorporation of the l-phenylalanine within the polymer.

Improving paclitaxel delivery: in vitro and in vivo characterization of PEGylated polyphosphoester-based nanocarriers.

Nanomaterials have great potential to offer effective treatment against devastating diseases by providing sustained release of high concentrations of therapeutic agents locally, especially when the route of administration allows for direct access to the diseased tissues. Biodegradable polyphosphoester-based polymeric micelles and shell cross-linked knedel-like nanoparticles (SCKs) have been designed from amphiphilic block-graft terpolymers, PEBP-b-PBYP-g-PEG, which effectively incorporate high concentrations of paclitaxel (PTX). Well-dispersed nanoparticles physically loaded with PTX were prepared, exhibiting desirable physiochemical characteristics. Encapsulation of 10 wt% PTX, into either micelles or SCKs, allowed for aqueous suspension of PTX at concentrations up to 4.8 mg/mL, as compared to <2.0 µg/mL for the aqueous solubility of the drug alone. Drug release studies indicated that PTX released from these nanostructures was defined through a structure-function relationship, whereby the half-life of sustained PTX release was doubled through cross-linking of the micellar structure to form SCKs. In vitro, physically loaded micellar and SCK nanotherapeutics demonstrated IC50 values against osteosarcoma cell lines, known to metastasize to the lungs (CCH-OS-O and SJSA), similar to the pharmaceutical Taxol formulation. Evaluation of these materials in vivo has provided an understanding of the effects of nanoparticle structure-function relationships on intratracheal delivery and related biodistribution and pharmacokinetics. Overall, we have demonstrated the potential of these novel nanotherapeutics toward future sustained release treatments via administration directly to the sites of lung metastases of osteosarcoma.

Holistic assessment of covalently labeled core-shell polymeric nanoparticles with fluorescent contrast agents for theranostic applications.

The successful development of degradable polymeric nanostructures as optical probes for use in nanotheranostic applications requires the intelligent design of materials such that their surface response, degradation, drug delivery, and imaging properties are all optimized. In the case of imaging, optimization must result in materials that allow differentiation between unbound optical contrast agents and labeled polymeric materials as they undergo degradation. In this study, we have shown that use of traditional electrophoretic gel-plate assays for the determination of the purity of dye-conjugated degradable nanoparticles is limited by polymer degradation characteristics. To overcome these limitations, we have outlined a holistic approach to evaluating dye and peptide-polymer nanoparticle conjugation by utilizing steady-state fluorescence, anisotropy, and emission and anisotropy lifetime decay profiles, through which nanoparticle-dye binding can be assessed independently of perturbations, such as those presented during the execution of electrolyte gel-based assays. This approach has been demonstrated to provide an overall understanding of the spectral signature-structure-function relationship, ascertaining key information on interactions between the fluorophore, polymer, and solvent components that have a direct and measurable impact on the emissive properties of the optical probe. The use of these powerful techniques provides feedback that can be utilized to improve nanotheranostics by evaluating dye emissivity in degradable nanotheranostic systems, which has become increasingly important as modern platforms transition to architectures intentionally reliant on degradation and built-in environmental responses.

Photoactive Spatial Proximity Probes for Binding Pairs with Epigenetic Marks.

A new strategy for encoding polypeptide libraries with photolabile tags is developed. The photoassisted assay, based on conditional release of encoding tags only from bound pairs, can differentiate between peptides which have minor differences in a form of post-translational modifications with epigenetic marks. The encoding strategy is fully compatible with automated peptide synthesis. The encoding pendants are compact and do not perturb potential binding interactions.

Polycarbonates derived from glucose via an organocatalytic approach.

An organocatalyzed ring-opening polymerization methodology was developed for the preparation of polycarbonates derived from glucose as a natural product starting material. The cyclic 4,6-carbonate monomer of glucose having the 1, 2, and 3 positions methyl-protected was prepared in three steps from a commercially available glucose derivative, and the structure was confirmed by means of NMR and IR spectroscopies, electrospray ionization mass spectrometry (MS), and single-crystal X-ray analysis. Polymerization of the monomer, initiated by 4-methylbenzyl alcohol in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene as the organocatalyst, proceeded effectively in a controlled fashion to afford the polycarbonate with a tunable degree of polymerization, narrow molecular weight distribution, and well-defined end groups, as confirmed by a combination of NMR spectroscopy, gel-permeation chromatography, and MALDI-TOF MS. A distribution of head-to-head, head-to-tail, and tail-to-tail regiochemistries was determined by NMR spectroscopy and tandem MS analysis by electron transfer dissociation. These polycarbonates are of interest as engineering materials because of their origination from renewable resources combined with their amorphous character and relatively high glass transition temperatures as determined by X-ray diffraction and differential scanning calorimetry studies.

Poly(D-glucose carbonate) block copolymers: a platform for natural product-based nanomaterials with Solvothermatic characteristics.

A natural product-based polymer platform, having the characteristics of being derived from renewable materials and capable of breaking down, ultimately, into natural byproducts, has been prepared through the ring-opening polymerization (ROP) of a glucose-based bicyclic carbonate monomer. ROP was carried out via chain extension of a polyphosphoester (PPE) macroinitiator in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) organocatalyst to afford the PPE-b-poly(D-glucose carbonate) (PDGC) block copolymer. This new copolymer represents a functional architecture that can be rapidly transformed through thiol-yne reactions along the PPE segment into a diverse variety of amphiphilic polymers, which interestingly display stimuli-sensitive phase behavior in the form of a lower critical solution temperature (LCST). Below the LCST, they undergo self-assembly to form spherical core-shell nanostructures that display a poorly defined core-shell morphology. It is expected that hydrophobic patches are exposed within the micellar corona, reminiscent of the surface complexity of proteins, making these materials of interest for triggered and reversible assembly disassembly processes.

Sensitivity of activatable reactive oxygen species probes by fluorescence spectroelectrochemistry.

We have developed a new analytical method of evaluating activatable fluorescent probes for ROS detection using integrated fluorescence spectroelectrochemistry. The Tafel formalism was applied to describe the process of the probes' oxidation under electrochemical conditions and identify a novel parameter defined as the threshold oxidation potential. This potential can serve as an approximation to the equilibrium potential and can be utilized for determining the sensitivity of a probe to oxidation. Based upon the measured values of threshold potentials, the order of sensitivity towards oxidation among several commonly used probes was determined to be the following (from highest to lowest): 2,7-dihydrodichlorofluorescein > dihydroethidium > dihydrorhodamine 123 > dihydrorhodamine 6G. The presented approach opens up a new direction in synthesizing and screening novel ROS probes with a well-defined sensitivity for in vitro and in vivo applications.

Defining a polymethine dye for fluorescence anisotropy applications in the near-infrared spectral range.

Fluorescence anisotropy in the near-infrared (NIR) spectral range is challenging because of the lack of appropriate NIR fluorescent labels. We have evaluated polymethine fluorescent dyes to identify a leading candidate for NIR anisotropy applications. The NIR dye LS601 demonstrated low fluorescence anisotropy values (r) as a result of its relatively long fluorescent lifetime 1.3 ns. The r value of LS601 unbound and coupled to biological macromolecules was found to have a sufficient dynamic range from 0.24 to 0.37, demonstrating the feasibility of fluorescence anisotropy in the NIR. The viability of fluorescence anisotropy using a NIR label was demonstrated by characterization of dye-protein conjugates. These results open the door to a number of applications in drug discovery, fluorescence anisotropy imaging and contrast agent development.

Externally sensitized deprotection of PPG-masked carbonyls as a spatial proximity probe in photoamplified detection of binding events.

Externally sensitized electron-transfer fragmentation in dithiane PPG (photoremovable protecting group)-protected carbonyls is adopted for detection and amplification of molecular recognition events. The new methodology allows for detection of as low as 50 attomoles of avidin utilizing an imager based on a low sensitivity mass-produced consumer CCD camera. Numeric modelling is carried out to demonstrate the intrinsic limitations of 2D amplification on surfaces and the advantages of unconstrained amplification in a compartmentalized volume of spatially addressable 3D solutions.

Photochemically amplified detection of molecular recognition events: an ultra-sensitive fluorescence turn-off binding assay.

Amplified fluorescence quenching methodology based on massive autocatalytic photo-unmasking of a dual function sensitizer-quencher is developed and adopted for photoassisted ultra-sensitive detection of molecular recognition events. The resulting binding assay, based on a molecular recognition-triggered photo-amplified cascade with concomitant decrease of fluorescence is validated with the biotin-avidin pair, achieving attomolar detection.

Controlled release of etoricoxib from poly(ester urea) films for post-operative pain management.

Medical prescriptions for the alleviation of post-surgical pain are the most abundant source of opioids in circulation. As a systemic drug delivery source, opioids leave patients at high risk for side effects after being dosed. Given the significant rate of unauthorized use, distribution, addiction, and opioid related deaths, an alternative method of post-surgical analgesia is needed. Herein, we report the use of bio-resorbable poly(ester urea) (PEU) films that controllably deliver a non-opioid COX-2 inhibitor, etoricoxib, in vivo and in vitro as a model system for post-surgical pain control. PEU composition, drug-load, and film thickness were varied to selectively control etoricoxib elution. Elution data were fit to a Higuchi model, and the diffusion constant of etoricoxib was calculated in each of the films. Pharmacokinetic (pK) data from an in vivo rat model showed the local tissue concentration of etoricoxib at the study endpoint to be up to 23-fold higher in tissue then plasma. In a well-established mouse model of diabetic neuropathic pain in vivo film implantation showed effective relief of pain for more than 4 days post-implantation and efficacious local etoricoxib delivery. Overall, implementation of local drug delivery systems such as this could reduce the need for opioid prescriptions associated with current pain management strategies.

3D printed capsules for quantitative regional absorption studies in the GI tract.

Drug development is a long process which requires careful evaluation of the drug substance (active pharmaceutical ingredient, API), drug product (tablet, capsule etc.) and the bioperformance (both pre-clinical and clinical) before testing the efficacy of the final dosage form. The earliest assessment of a new drug substance requires an understanding of the safety and clinical performance (Phase 1) wherein faster processes (like on-site formulation strategy) have been set in place for quick clinical read-outs. One key gap that exists in this early assessment is the ability to evaluate modified release drug products. Here, an additive manufacturing approach is used to prepare polyvinyl alcohol (PVA) capsule shells using 3D printing (3DP), where the shells can be filled with either a solid or a liquid vehicle containing the API. In this work we demonstrate how we can delay the release of the API from the printed capsules allowing us to evaluate regional absorption in pre-clinical studies. By using 3DP, a new method to provide a series of release profiles is demonstrated, where the induction time of a delayed burst release is controlled by the wall thicknesses of printed capsules. New hanging baskets were also designed and 3D printed for the dissolution tests to better understand the rupturing of these capsules in an USP 2 dissolution apparatus. By controlling the wall thickness of the capsule, the induction time of drug release can be controlled from 12 to 198 min. This wide range of induction times demonstrated with this 3DP strategy is not currently available in a commercially available oral drug product form. Varying the induction times to the drug release to interrogate different regions of the GI tract is exhibited in vivo (beagle dogs) and initial analysis suggested a good in vitro/in vivo relationship (IVIVR).

Tungsten-loaded SMP foam nanocomposites with inherent radiopacity and tunable thermo-mechanical properties.

Shape memory polymer (SMP) foams have been developed for use in neurovascular occlusion applications. These materials are predominantly polyurethanes that are known for their biocompatibility and tunable properties. However, these polymers inherently lack X-ray visibility, which is a significant challenge for their use as implantable materials. Herein, low density, highly porous shape memory polyurethane foams were developed with tungsten nanoparticles dispersed into the foam matrix, at increasing concentrations, to serve as a radiopaque agent. Utilizing X-ray fluoroscopy sufficient visibility of the foams at small geometries was observed. Thermal characterization of the foams indicated altered thermal response and delayed foam actuation with increasing nanoparticle loading (because of restricted network mobility). Mechanical testing indicated decreased toughness and strength for higher loading because of disruption of the SMP matrix. Overall, filler addition imparted x-ray visibility to the SMP foams and allowed for tuned control of the transition temperature and actuation kinetics for the material.

In vivo fate tracking of degradable nanoparticles for lung gene transfer using PET and Cerenkov imaging.

Nanoparticles (NPs) play expanding roles in biomedical applications including imaging and therapy, however, their long-term fate and clearance profiles have yet to be fully characterized in vivo. NP delivery via the airway is particularly challenging, as the clearance may be inefficient and lung immune responses complex. Thus, specific material design is required for cargo delivery and quantitative, noninvasive methods are needed to characterize NP pharmacokinetics. Here, biocompatible poly(acrylamidoethylamine)-b-poly(dl-lactide) block copolymer-based degradable, cationic, shell-cross-linked knedel-like NPs (Dg-cSCKs) were employed to transfect plasmid DNA. Radioactive and optical beacons were attached to monitor biodistribution and imaging. The preferential release of cargo in acidic conditions provided enhanced transfection efficiency compared to non-degradable counterparts. In vivo gene transfer to the lung was correlated with NP pharmacokinetics by radiolabeling Dg-cSCKs and performing quantitative biodistribution with parallel positron emission tomography and Cerenkov imaging. Quantitation of imaging over 14 days corresponded with the pharmacokinetics of NP movement from the lung to gastrointestinal and renal routes, consistent with predicted degradation and excretion. This ability to noninvasively and accurately track NP fate highlights the advantage of incorporating multifunctionality into particle design.

Examination of radio-opacity enhancing additives in shape memory polyurethane foams.

Three microparticle additives, tungsten (W), zirconium oxide (ZrO2), and barium sulfate (BaSO4) were selected to enhance the radio-opacity in shape memory polymer (SMP) foam biomaterials. The addition of filler causes no significant alterations of glass transition temperatures, density of the materials increases, pore diameter decreases, and total volume recovery decreases from approximately 70 times in unfilled foams to 20 times (4% W and 10% ZrO2). The addition of W increases time to recovery; ZrO2 causes little variation in time to shape recovery; BaSO4 increases the time to recovery. On a 2.00 mean X-ray density (mean X.D.) scale, a GDC coil standard has a mean X.D. of 0.62; 4% W enhances the mean X.D. to 1.89, 10% ZrO2 to 1.39 and 4% BaSO4 to 0.74. Radio-opacity enhancing additives could be used to produce SMP foams with controlled shape memory kinetics, low density, and enhanced X-ray opacity for medical materials.

Design of irreversible optical nanothermometers for thermal ablations.

Nanothermometers composed from a gold nanorod core, temperature sensitive linker and fluorescent dye are reported. The nanothermometers have low fluorescence due to a self-quenching mechanism at temperatures below 50 °C and become highly fluorescence above 70 °C.

Evaluation of inflammatory response to acute ischemia using near-infrared fluorescent reactive oxygen sensors.

PURPOSE: Ischemia-related processes associated with the generation of inflammatory molecules such as reactive oxygen species (ROS) are difficult to detect at the acute stage before the physiologic and anatomic evidence of tissue damage is present. Evaluation of the inflammatory and healing response early after an ischemic event in vivo will aid in treatment selection and patient outcomes. We introduce a novel near-infrared hydrocyanine molecular probe for the detection of ROS as a marker of tissue response to ischemia and a precursor to angiogenesis and remodeling. The synthesized molecular probe, initially a non-fluorescent hydrocyanine conjugated to polyethylene glycol, converts to a highly fluorescent cyanine reporter upon oxidation. PROCEDURES: The probe was applied in a preclinical mouse model for myocardial infarction, where ligation and removal of a portion of the femoral artery in the hindlimb resulted in temporary ischemia followed by angiogenesis and healing. RESULTS: The observed increase in fluorescence intensity was approximately sixfold over 24 h in the ischemic tissue relative to the uninjured control limb and was attributed to the higher concentration of ROS in the ischemic tissue. CONCLUSIONS: These results demonstrate the potential for non-invasive sensing for interrogating the inflammatory and healing response in ischemic tissue.

BLOOD TRIGGERED RAPID RELEASE POROUS NANOCAPSULES.

Rapid-release drug delivery systems present a new paradigm in emergency care treatments. Such systems combine a long shelf life with the ability to provide a significant dose of the drug to the bloodstream in the shortest period of time. Until now, development of delivery formulations has concentrated on slow release systems to ensure a steady concentration of the drug. To address the need for quick release system, we created hollow polyacrylate nanocapsules with nanometer-thin porous walls. Burst release occurs upon interaction with blood components that leads to escape of the cargo. The likely mechanism of release involves a conformational change of the polymer shell caused by binding albumin. To demonstrate this concept, a near-infrared fluorescent dye indocyanine green (ICG) was incorporated inside the nanocapsules. ICG-loaded nanocapsules demonstrated remarkable shelf life in aqueous buffers with no release of ICG for twelve months. Rapid release of the dye was demonstrated first in vitro using albumin solution and serum. SEM and light scattering analysis demonstrated the retention of the nanocapsule architecture after the release of the dye upon contact with albumin. In vivo studies using fluorescence lifetime imaging confirmed quick discharge of ICG from the nanocapsules following intravenous injection.

A NIR Dye for Development of Peripheral Nerve Targeted Probes.

Current imaging modalities lack the ability to quickly assess and classify nerve injury for predicting favourable versus unfavourable healing outcomes, which could minimize episodes of chronic pain and loss of function by allowing for early intervention. Thus, the development of a technique to noninvasively assess peripheral nerve damage is of critical importance. While the development of nerve specific near infrared (NIR) molecular probes capable of such diagnostics constitutes our long term goal, initial studies to identify a NIR dye for constructing such a probe are required. We have evaluated the properties of a novel highly hydrophilic and functionalizable polymethine dye, and its more hydrophobic analogue indocyanine green, within the sciatic nerve of rats following intra-nerve injection. The reporting ability of both dyes at critical depths for nerve imaging, the importance of hydrophilicity on dye transport through nervous tissue, and their toxicity - or lack thereof - to the neural environment have been evaluated. The results suggest that the novel NIR dye is an appropriate fluorescent reporter for use in designing nerve-specific optical molecular probes for non-invasive diagnosis and classification of nerve injury.