Light-Based 3D Printing of Gelatin-Based Biomaterial Inks to Create a Physiologically Relevant In Vitro Fish Intestinal Model

To provide prominent accessibility of fishmeal to the European population, the currently available, time- and cost-extensive feeding trials, which evaluate fish feed, should be replaced. The current paper reports on the development of a novel 3D culture platform, mimicking the microenvironment of the intestinal mucosa in vitro. The key requirements of the model include sufficient permeability for nutrients and medium-size marker molecules (equilibrium within 24 h), suitable mechanical properties (G' < 10 kPa), and close morphological similarity to the intestinal architecture. To enable processability with light-based 3D printing, a gelatin-methacryloyl-aminoethyl-methacrylate-based biomaterial ink is developed and combined with Tween 20 as porogen to ensure sufficient permeability. To assess the permeability properties of the hydrogels, a static diffusion setup is utilized, indicating that the hydrogel constructs are permeable for a medium size marker molecule (FITC-dextran 4 kg mol⁻¹). Moreover, the mechanical evaluation through rheology evidence a physiologically relevant scaffold stiffness (G' = 4.83 ± 0.78 kPa). Digital light processing-based 3D printing of porogen-containing hydrogels results in the creation of constructs exhibiting a physiologically relevant microarchitecture as evidenced through cryo-scanning electron microscopy. Finally, the combination of the scaffolds with a novel rainbow trout (Oncorhynchus mykiss) intestinal epithelial cell line (RTdi-MI) evidence scaffold biocompatibility.     

Synthesis of novel dimeric cationic lipids based on an aromatic backbone between the hydrocarbon chains and headgroup

Seven dimeric cationic lipids possessing an aromatic anchor between the hydrocarbon chains and cationic headgroup have been synthesized. The spacers in these lipids vary in length, hydrophobicity and flexibility. The synthesis, membrane-forming properties and complexation with plasmid DNA (lipoplex formation) are briefly described.     

Synthesis and vesicular polymerization of novel counter‐ion polymerizable/crosslinkable surfactants

Two novel two‐tail surfactants, dicetyldimethylammonium 4‐vinyl benzoate (DDVB) and dicetyldimethylammonium 3,5‐divinyl benzoate (DDDB), were synthesized by neutralizing the corresponding quaternary ammonium hydroxide with the appropriate benzoic acid. As expected, these surfactants formed both homo and mixed‐vesicles, which were readily polymerized with a suitable radical photo‐initiator. The polymerization process was followed by UV–vis spectroscopy and also reconfirmed by NMR and IR spectroscopy. Polymerization of vesicles prepared from DDVB, unlike the more commonly polymerized vesicles, in which the polymerizable group forms an integral part of the surfactant, leads to the formation of a linear polyelectrolyte chain that is only electrostatically bound to the lipid bilayer. On the other hand, polymerization of DDDB vesicles leads to the formation of a crosslinked shell (or net) that encases the vesicle bilayer. Such counterion crosslinked vesicles were shown to be resistant to destabilization both by lysis as well as in the presence of a fairly high volume fraction of an organic solvent, such as ethanol. However, although the simple polymerized (linearly) vesicles, formed from DDVB, exhibit enhanced stability toward lysis when compared to their unpolymerized counterparts, they are readily destabilized in the presence of ethanol, leading to precipitation. This sharp contrast in the behavior of linearly polymerized and crosslinked systems suggests that crosslinking is essential to arrest conformational reorganization of the polyelectrolyte chains induced by a change in the solvent medium, which in turn leads to precipitation. Such counterion crosslinked vesicular systems also have an added advantage; they may retain the fluidityof the lipid bilayer while at the same time possess enhanced stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5271–5283, 2004     

Local Heat Transfer Distribution in a Rectangular Pin Channel With and Without Vortex Generators

Short pin fins are used to enhance heat transfer rates by increasing the level of turbulence in the trailing edge of gas turbine blades. Experiments are conducted to investigate the local Nusselt number distributions in a staggered pin-fin array using the infrared thermal imaging technique. The pin fins are arranged in a rectangular channel with an aspect ratio of 9. The pins have streamwise pitch-to-diameter (X_S/D) and spanwise pitch-to-diameter (X_T/D) ratios of 2 with a pin height-to-diameter (H/D) ratio of 2. Ejection holes of 5-mm diameter with a pitch of 12.7 mm are used to study the effects of lateral ejection. Both one-wall and two-wall heating situations are studied for straight-flow and lateral-ejection cases. It is found that the local Nusselt numbers are highest below the horseshoe vortices just upstream of the individual pin fins. For the straight-flow case, the Nusselt numbers for the two-wall heating case are observed to be 15–20% higher than those of the one-wall heating case. Lateral ejection causes a decrease of about 1–10% for the one-wall heating case, while there is an increase of about 10% for the two-wall heating case. Experiments are also carried out with vortex generators between individual pin fins. Vortex generators cause an increase in heat transfer by about 50% compared to the straight-flow cases.     

Icosahedral DNA Nanocapsules by Modular Assembly

It's a trap! DNA polyhedra formed through molecular self‐assembly may function as nanocapsules for the targeted delivery of encapsulated entities. This functional aspect was demonstrated for the most complex DNA‐based platonic solid: During the stepwise amalgamation of discrete polyhedra to form icosahedra, gold nanoparticles (GNPs) were encapsulated from solution (see illustration and TEM image of icosahedral cages containing GNPs).

     

Ag@AgI, core@shell structure in agarose matrix as hybrid: synthesis, characterization, and antimicrobial activity

A novel in situ core@shell structure consisting of nanoparticles of Ag (Ag Nps) and AgI in agarose matrix (Ag@AgI/agarose) has been synthesized as a hybrid, in order to have an efficient antibacterial agent for repetitive usage with no toxicity. The synthesized core@shell structure is very well characterized by XRD, UV-visible, photoluminescence, and TEM. A detailed antibacterial studies including repetitive cycles are carried out on Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria in saline water, both in dark and on exposure to visible light. The hybrid could be recycled for the antibacterial activity and is nontoxic toward human cervical cancer cells (HeLa cells). The water insoluble Ag@AgI in agarose matrix forms a good coating on quartz, having good mechanical strength. EPR and TEM studies are carried out on the Ag@AgI/agarose and the bacteria, respectively, to elucidate a possible mechanism for killing of the bacteria.     

Using steric hindrance to design new inhibitors of class C beta-lactamases

beta-lactamases confer resistance to beta-lactam antibiotics such as penicillins and cephalosporins. However, beta-lactams that form an acyl-intermediate with the enzyme but subsequently are hindered from forming a catalytically competent conformation seem to be inhibitors of beta-lactamases. This inhibition may be imparted by specific groups on the ubiquitous R(1) side chain of beta-lactams, such as the 2-amino-4-thiazolyl methoxyimino (ATMO) group common among third-generation cephalosporins. Using steric hindrance of deacylation as a design guide, penicillin and carbacephem substrates were converted into effective beta-lactamase inhibitors and antiresistance antibiotics. To investigate the structural bases of inhibition, the crystal structures of the acyl-adducts of the penicillin substrate amoxicillin and the new analogous inhibitor ATMO-penicillin were determined. ATMO-penicillin binds in a catalytically incompetent conformation resembling that adopted by third-generation cephalosporins, demonstrating the transferability of such sterically hindered groups in inhibitor design.