Biopolymer albumin for diagnosis and in drug delivery

Ketotifen controlled release from cellulose acetate propionate and cellulose acetate butyrate membranes

Ketotifen was immobilised in cellulose acetate propionate (CAP) membranes and in cellulose acetate butyrate (CAB) membranes. The characteristics of each system were evaluated under a range of experimental conditions. The topography and uniformity of the membranes was assessed using scanning electron microscopy. The release characteristics associated with Ketotifen were monitored spectrophotometrically. The swelling capacity of the membranes was evaluated and attributed to the combined effects of diffusion and of complex dissociation, during swelling. The materials produced were able to provide controlled release of Ketotifen due to their controlled swelling behaviour and adequate release properties. The results showed that the release of Ketotifen from the CAB membranes is higher but the release from the CAP membranes is more uniform.

Self-assembly of β-casein and lysozyme

The self-assembly of beta-casein and lysozyme, a linear and a globular protein with isoelectric point of pH 5.0 and 10.7, respectively, was studied. Polydisperse electrostatic complex micelles formed when mixing beta-casein and lysozyme aqueous solutions. After the micelle solution was heated, lysozyme gelated and beta-casein was trapped in the gel, producing narrowly dispersed nanoparticles. The nanoparticles were characterized with laser light scattering, zeta-potential, steady state fluorescence, atomic force microscopy, and transmission electron microscopy. The nanoparticles have spherical shape and their sizes depend on the pH of the heat treatment and the molar ratio of beta-casein to lysozyme. The nanoparticles display amphoteric property and are relatively hydrophobic at pH around 5 and around 10. The net charges on the surface stabilize the nanoparticles in the solution.

Particulation of hyperbranched aromatic biopolyesters self-organized by solvent transformation in ionic liquids

Hyperbranched copolymers were prepared by the heat transesterification of 4-hydroxycinnamic acid (4HCA) and 3,4-dihydroxycinnamic acid (DHCA) with a high 4HCA composition dissolved in trifluoroacetic acid (TFA). The nanoparticles were formed after two homogeneous copolymer solutions were mixed in DMF and TFA, which are both good solvents for the copolymer P(4HCA-co-DHCA). We confirmed that the driving force for particulation was solvent interactions that produce ion pairs, which elevate the polarity of the solvent too much to solubilize the copolymers.

Comparison between Protein−Polyethylene Glycol (PEG) Interactions and the Effect of PEG on Protein−Protein Interactions Using the Liquid−Liquid Phase Transition

Phase transitions of protein aqueous solutions are important for protein crystallization and biomaterials science in general. One source of thermodynamic complexity in protein solutions and their phase transitions is the required presence of additives such as polyethylene glycol (PEG). To investigate the effects of PEG on the thermodynamic behavior of protein solutions, we report measurements on the liquid-liquid phase separation (LLPS) of aqueous bovine serum albumin (BSA) in the presence of relatively small amounts of PEG with an average molecular weight of 1450 g/mol (PEG1450) as a model system. We experimentally characterize two thermodynamically independent properties of the phase boundary: (1) the effect of PEG1450 concentration on the LLPS temperature, (2) BSA/PEG1450 partitioning in the two liquid coexisting phases. We then use a thermodynamic perturbation theory to relate the first property to the effect of PEG concentration on protein-protein interactions and the second property to protein-PEG interactions. As criteria to determine the accuracy of a microscopic model, we examine the model's ability to describe both experimental thermodynamic properties. We believe that the parallel examination of these two properties is a valuable tool for verifying the validity of existing models and for developing more accurate ones. For our system, we have found that a depletion-interaction model satisfactorily explains both protein-PEG interactions and the effect of PEG concentration on protein-protein interactions. Finally, due to the general importance of LLPS, we will experimentally show that protein-PEG-buffer mixtures can exhibit two distinct types of liquid-liquid phase transitions.

Synthesis and Magnetic Properties of Biocompatible Hybrid Hollow Spheres

Magnetic hybrid hollow spheres of about 200 nm were prepared by a core-template-free route, that is, adding Fe3O4 nanoparticles stabilized by poly(vinyl alcohol) (PVA) to an aqueous solution of polymer-monomer pairs composed of a cationic polymer, chitosan (CS), and an anionic monomer, acrylic acid (AA), followed by polymerization of acrylic acid and selective cross-linking of chitosan at the end of polymerization. The obtained hybrid spheres were characterized by dynamic light scattering (DLS) in aqueous solution and observed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) in the solid state. Fourier transform infrared spectroscopy (FTIR) and X-ray and electron diffractions revealed that the Fe3O4 nanoparticles were incorporated into the shells of chitosan-poly(acrylic acid) (CS-AA) hollow spheres. Magnetization studies and Mössbauer spectroscopy suggested that the chains (or islands) of iron oxide nanoparticles were most likely formed in the walls of the hollow spheres. The phantom test of magnetic resonance imaging showed that the synthesized hybrid hollow spheres had a significant magnetic resonance signal enhancement in T2-weighted image.

Nanoencapsulation I. Methods for preparation of drug-loaded polymeric nanoparticles

Polymeric nanoparticles have been extensively studied as particulate carriers in the pharmaceutical and medical fields, because they show promise as drug delivery systems as a result of their controlled- and sustained-release properties, subcellular size, and biocompatibility with tissue and cells. Several methods to prepare nanoparticles have been developed during the last two decades, classified according to whether the particle formation involves a polymerization reaction or arises from a macromolecule or preformed polymer. In this review the most important preparation methods are described, especially those that make use of natural polymers. Advantages and disadvantages will be presented so as to facilitate selection of an appropriate nanoencapsulation method according to a particular application.

pH-sensitive hydrogels based on bovine serum albumin for oral drug delivery

pH-sensitive bovine serum albumin (BSA) hydrophilic microspheres were prepared by free radical polymerization of methacrylate derivatized BSA and methacrylic acid sodium salt. Incorporation of both monomers in hydrogels was confirmed by Fourier transform infrared spectroscopy. Morphological analysis by scanning electron microscopy showed spherical shape and porous surface of all prepared samples. The microspheres showed high water affinity at neutral pH values and a narrow dimensional distribution. Network density of hydrogels depends on derivatization degree (DD%) of BSA and/or concentration of modified BSA in the polymerization feed. In order to employ the prepared samples such as pH-sensitive hydrogels, in vitro release studies, in media simulating biological fluids, were performed using diflunisal (DF) and beta-propranolol (PR) as model drugs. Experimental data showed that the release profiles depend on drug-matrix interactions and diffusional limitation awardable to crosslinking degree of microparticles. beta-Propranolol is quickly released at pH 1.0 and a complete release after 1 h at pH 6.8 was observed. In the case of diflunisal pH-sensitive release was observed. At pH 1.0 low amounts of drug were released (w/w<10% after 2 h). When the pH is 6.8, the diflunisal release increased in the amount (w/w>75% after 24 h).

Micellization of casein-graft-dextran copolymer prepared through Maillard reaction

Casein is almost insoluble at around pH 4.6, which is its isoelectric point (pI). Grafting copolymer, casein-g-dextran, was prepared through the Amadori rearrangement of the Maillard reaction. The copolymer has a reversible pH sensitive property: micellization at the pI of casein forming a casein core and dextran shell structure and dissociation when pH differs from the pI. The micelles produced at pH 4.6 have a spherical shape and their size is dependent on the Maillard reaction: reaction time, molar ratio of casein to dextran, and molecular weight of dextran used. Typically, the hydrodynamic diameter of the micelles is about 100 nm and the critical micelle concentration is about 10 mg/L. The micelles are very stable in aqueous solution and can be stored as lyophiled powder. The micelles are able to encapsulate hydrophobic compounds such as pyrene.