Melanie McNeil

Nanogel Star Polymer Architectures: A Nanoparticle Platform for Modular Programmable Macromolecular Self-Assembly, Intercellular Transport, and Dual-Mode Cargo Delivery

There is a growing demand for the simultaneous, site-localized delivery and expression of tandem functionality within the human body. [1–7] The benefits of dual delivery of functional cargos such as two (synergistic) therapeutics, [8,9] a therapeutic and an imaging agent, [4,10] or dual-mode imaging agents [11,12] have all been recently reported. For many medical applications requiring such in vivo expression of exogenous functional materials, the use of polymeric nanoparticle delivery vehicles of increasingly complex design is envisioned. Currently, organic nanoparticle platforms under development for these purposes include liposomes, [13] dendrimers,[14] and micelles. [15] Alternatively, star polymers (unimolecular, globular, polymer architectures) are an increasingly attractive class of organic nanoparticles for biomedical research purposes. [16–18] Although topographically similar to dendrimers (i.e., a high local density of polymeric arms, surface functionality, and interstitial regions), they lack the synthetic and structural limitations of dendrimers [19,20] and the dynamic instability of micelles [21] and liposomes. [22] Nanogel star polymers, i.e., those with polymer “arms” emanating from a cross-linked polymer core, [23,24] in particular, offer a potential for variation in nanoparticle structure and surface functional, i.e., arm density but are among the most synthetically demanding of polymeric nanostructures to develop. [25–29]

Advanced chemical recycling of poly(ethylene terephthalate) through organocatalytic aminolysis

We report the effective organocatalysis of the aminolytic depolymerization of waste poly(ethylene terephthalate) (PET) using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) producing a broad range of crystalline terephthalamides. This diverse set of monomers possesses great potential as building blocks for high performance materials with desirable thermal and mechanical properties deriving from the terephthalic moiety and amide hydrogen bonding. Further, a computational study established mechanistic insight into self-catalyzed and organocatalyzed aminolysis of terephthalic esters, suggesting that the bifunctionality of TBD particularly concerning activation of the carbonyl group differentiates TBD from other organic bases.

Fickian-Based Empirical Approach for Diffusivity Determination in Hollow Alginate-Based Microfibers Using 2D Fluorescence Microscopy and Comparison with Theoretical Predictions

Hollow alginate microfibers (od = 1.3 mm, id = 0.9 mm, th = 400 µm, L = 3.5 cm) comprised of 2% (w/v) medium molecular weight alginate cross-linked with 0.9 M CaCl2 were fabricated to model outward diffusion capture by 2D fluorescent microscopy. A two-fold comparison of diffusivity determination based on real-time diffusion of Fluorescein isothiocyanate molecular weight (FITC MW) markers was conducted using a proposed Fickian-based approach in conjunction with a previously established numerical model developed based on spectrophotometric data. Computed empirical/numerical (Dempiricial/Dnumerical) diffusivities characterized by small standard deviations for the 4-, 70- and 500-kDa markers expressed in m2/s are (1.06 × 10−9 ± 1.96 × 10−10)/(2.03 × 10−11), (5.89 × 10−11 ± 2.83 × 10−12)/(4.6 × 10−12) and (4.89 × 10−12 ± 3.94 × 10−13)/(1.27 × 10−12), respectively, with the discrimination between the computation techniques narrowing down as a function of MW. The use of the numerical approach is recommended for fluorescence-based measurements as the standard computational method for effective diffusivity determination until capture rates (minimum 12 fps for the 4-kDa marker) and the use of linear instead of polynomial interpolating functions to model temporal intensity gradients have been proven to minimize the extent of systematic errors associated with the proposed empirical method.

An experimental study of concentration forcing applied to the methanol synthesis reaction

Abstract The effect of square-wave concentration-forcing operation on the rate of methanol production over two industrial catalysts was studied at 513 K and 2.86 MPa total pressure. Improvements as high as 25 percent relative to the optimal steady-state methanol production rate, in moles per gram catalyst per unit time, were obtained over BASFs S 3-85 catalyst. This occurred in a laboratory-scale fixed-bed reactor with gas mixing for a cycling time of τ = 12 seconds and for a cycle split relative to carbon monoxide of γCO = 0.20, the rest of the cycle being hydrogen. Improvements as high as 15 percent were also obtained over Imperial Chemical Industries ICI 51-2 catalyst, in a differential plug-flow reactor for τ = 24 seconds and γCO = 0.15. These improvements were obtained for pure-component steady cycling between carbon monoxide and hydrogen with a constant carbon dioxide molar concentration of 2 per cent (BASF catalyst) or 3 percent (ICI catalyst) present in both parts of the cycle. On the other hand,...

Effect of artificial cell miniaturization on urea degradation by immobilized E. coli DH5α (pKAU17)

Abstract Second generation E. coli DH5α (pKAU17) was successfully encapsulated by means of atomization (MA), inkjet printing (MI) and double-encapsulation (DDMI) for the purpose of urea degradation in a simulated uremic medium at 37 °C. Experimentally determined values of the effectiveness factor are 0.83, 0.28 and 0.34 for the MI, MA and DDMI capsules, respectively, suggesting that the catalytic activity of the E. coli DH5α (pKAU17) immobilized in MI capsule (d = 52 μm ± 2.7 μm) is significantly less diffusion-limited than in the case of the MA (d = 1558 μm ± 125 μm) and DDMI (d = 1370 μm ± 60 μm) bio-encapsulation schemes at the 98.3% CI. The proposed novel double encapsulation biofabrication method for alginate-based microspheres, characterized by lower membrane degradation rates due to secondary containment is recommended compared to the standard atomization scheme currently adopted across immobilization-based therapeutic scenarios. A Fickian-based mechanism is proposed with simulations mimicking urea degradation for a single capsule for the atomization and the inkjet schemes.