Wave propagation in micro-heterogeneous porous media: a model based on an integro-differential wave equation

A model hyperbolic partial differential equation with singular convolution operators and infinitely smooth solutions is studied. It is shown that short pulses, including finite-bandwidth pulses, propagate with a delay with respect to the wavefront. For a two-parameter family of such equations Green's functions are obtained in a simple self-similar form. As an application, it is demonstrated that the Gurevich-Lopatnikov dispersion law for a thin-layered porous medium can be approximated by a hyperbolic equation with singular memory.     

Synthesis and self-assembly behavior of novel polyaspartamide derivatives for anti-tumor drug delivery

A series of amphiphilic graft copolymers based on polyaspartamide were synthesized by a successive aminolysis reaction of polysuccinimide using 2-diisopropylaminoethyl (DIP) and laurylamine as a pH sensitive and hydrophobic group, respectively. The pH-dependent self-assembly behavior of the aqueous copolymer solution was investigated. Nano-aggregation occurred at a pH in the vicinity of the pKa of the DIP group, which was induced by a hydrophilic–hydrophobic shift of the DIP group in solution. The mean diameter of the nano-aggregate could be modulated by changing the composition of both pendants. The mean diameter of the nanoparticles increased with increasing solution pH from 6.5 to 8. At pH 8, the mean diameter of the nanoparticles increased rapidly at the temperature above 45 °C, probably due to the change in hydrophilic–hydrophobic balance of the pH-sensitive DIP moiety. The dissolution of paclitaxel (PTX) into this amphiphilic nanoparticle was attempted and the pH-dependent release behavior was examined with the stability study of the particle. The results showed significantly faster release of PTX at pH 6.5, which is a tumoral acidic pH, than in a neutral physiological pH. These thermo- and pH-sensitive polyaspartamide derivatives have potential use as a tumor-targeting delivery.     

Recombinant Single-Chain Antibody with the Trojan Peptide Penetratin Positioned in the Linker Region Enables Cargo Transfer Across the Blood–Brain Barrier

Delivery of therapeutic proteins into tissues and across the blood–brain barrier (BBB) is limited by the size and biochemical properties of the proteins. Efficient delivery across BBB is generally restricted to small, highly lipophilic molecules. However, in the last decades, several peptides that can pass cell membranes have been identified. It has been shown that these peptides are also capable of delivering large hydrophilic cargoes into cells and are therefore a powerful biological tool for transporting drugs across cell membranes and even into the brain. We designed and prepared a single-chain antibody fragment (scFvs), specific for the pathological form of the prion protein (PrP^Sc), where a cell-penetrating peptide (CPP) was used as a linker between the two variable domains of the scFv. The intravenously administered recombinant scFv-CPP was successfully targeted to and delivered into mouse brain cells. Our single-chain antibody fragments are of special interest in view of possible therapeutic reagents design not only for prion diseases but also for other neurodegenerative diseases.     

Physical and chemical changes in feather keratin during pyrolysis

The structural changes of chicken feather fibers (CFF) were investigated during pyrolysis by thermal analysis techniques coupled with mass spectrometry, solubility tests and gel permeation chromatography. The experimental data showed simultaneous disulfide bond cleavage and peptide crosslinking reactions, and suggested the dependency of crystalline melting on disulfide bond cleavage. The variation in the kinetics of these reactions played an important role in the melting transition and stability. Thus, careful tuning of the pyrolysis thermal profile provided conditions to obtain useful fibrous material at high temperatures. For instance, long-time heat treatments below the melting point provided sufficient crosslinks in the protein matrix to keep the fibrous structure intact. The protein matrix went through a series of transformations including cyclization and aromatization reactions above the melting point. Degradation of the matrix and liberation of aromatic carbons and cyclic amines were observed during these transformations. These pyrolysis mechanisms can serve as a guide for producing materials with desired properties from CFF and other keratin fibers, particularly in textile, high performance composite and catalyst applications.     

Efficient one-pot synthesis of β-phosphono malonates and 2-amino-4H-chromen-4-ylphosphonate derivatives by ethylenediamine diacetate-catalyzed three-component reactions

One-pot three-component reactions of arylaldehyde or salicylaldehyde with malononitrile (or ethylcyanoacetate) and triethyl phosphite are carried out in the presence of ethylenediamine diacetate (EDDA) as a catalyst for the synthesis of biologically interesting β-phosphono malonates and 2-amino-4H-chromen-4-ylphosphonate derivatives. The value of this method lies in its mild reaction catalyst and conditions, good yields, and ease of handling.