Impact of Freeze- and Spray-Drying Microencapsulation Techniques on ß-Glucan Powder Biological Activity: A Comparative Study.

The study compares the impact of freeze- and spray-drying (FD, SD) microencapsulation methods on the content of ß-glucan, total polyphenols (TP), total flavonoids (TF), phenolic acids (PA), and antioxidant activity (AA) in commercially ß-glucan powder (Pleurotus ostreatus) using maltodextrin as a carrier. Morphology (scanning electron microscopy- SEM), yield, moisture content (MC), and water activity (aw) were also evaluated in the samples. Our examinations revealed significant structural differences between powders microencapsulated by the drying methods. As compared to non-encapsulated powder, the SD powder with yield of 44.38 ± 0.55% exhibited more reduced (p < 0.05) values for aw (0.456 ± 0.001) and MC (8.90 ± 0.44%) than the FD one (yield: 27.97 ± 0.33%; aw: 0.506 ± 0.002; MC: 11.30 ± 0.28%). In addition, the highest values for ß-glucan content (72.39 ± 0.38%), TPC (3.40 ± 0.17 mg GAE/g), and TFC (3.07 ± 0.29 mg QE/g) have been detected in the SD powder. Our results allow for the conclusion that the SD microencapsulation method using maltodextrin seems to be more powerful in terms of the ß-glucan powder yield and its contents of ß-glucan, TP, and TF as compared to the FD technique.

Composition, antibacterial and antioxidant activities of Pimpinella saxifraga essential oil and application to cheese preservation as coating additive.

The effect of Pimpinella saxifraga essential oil (PSEO) addition (1-3%) in sodium alginate coating on the bacterial and oxidative stability of cheese was studied during refrigerated storage. The GC-HRMS analysis of PSEO showed that anethole, pseudoisoeugenol and p-anisaldehyde were the main components. The PSEO exhibited strong in vitro DPPH radical scavenging activity (IC50 = 6.81 µg/mL), ß-carotene bleaching inhibition (IC50 = 206 µg/mL), ferric reducing power (EC50 = 35.20 µg/mL), total antioxidant activity (213.96 ±â€¯11.12 µmol/mL α-tocopherol equivalent) and notable DNA protection potential. Additionally, PSEO displayed potent antibacterial activity against 3 Gram-positive and 3 Gram-negative bacteria (MICs = 0.78-3.12 mg/mL). The acute toxicity of PSEO was determined using mice model (LD50 = 976.2 mg/kg). The enrichment of sodium alginate coating with PSEO, particularly at 3%, improved cheese preservation by reducing the weight loss, preserving the pH and color and enhancing oxidative and bacterial stability without unpleased flavor for consumers.

Enzyme-Initiated Free-Radical Polymerization of Molecularly Imprinted Polymer Nanogels on a Solid Phase with an Immobilized Radical Source.

An enzyme-mediated synthetic approach is described for the preparation of molecularly imprinted polymer nanoparticles (MIP-NPs) in aqueous media. Horseradish peroxidase (HRP) was used to initiate the polymerization of methacrylate or vinyl monomers and cross-linkers by catalyzing the generation of free radicals. To prevent entrapment of the enzyme in the cross-linked polymer, and to enable it to be reused, HRP was immobilized on a solid support. MIPs based on 4-vinylpyridine and 1,4-bis(acryloyl)piperazine for the recognition of 2,4-dichlorophenoxyacetic acid (2,4-D) and salicylic acid were synthesized in an aqueous medium. MIPs for the protein trypsin were also synthesized. MIP nanoparticles with sizes between 50 and 300 nm were obtained with good binding properties, a good imprinting effect, and high selectivity for the target molecule. The reusability of immobilized HRP for MIP synthesis was shown for several batches.

Molecularly imprinted polymer nanomaterials and nanocomposites: atom-transfer radical polymerization with acidic monomers.

Molecularly imprinted polymers (MIPs) are artificial receptors which can be tailored to bind target molecules specifically. A new method, using photoinitiated atom-transfer radical polymerization (ATRP) for their synthesis as monoliths, thin films and nanoparticles is described. The synthesis takes place at room temperature and is compatible with acidic monomers, two major limitations for the use of ATRP with MIPs. The method has been validated with MIPs specific for the drugs testosterone and S-propranolol. This study considerably widens the range of functional monomers and thus molecular templates which can be used when MIPs are synthesized by ATRP, as well as the range of physical forms of these antibody mimics, in particular films and lithographic patterns, and their post-functionalization from living chain-ends.

Surface-imprinted nanofilaments for europium-amplified luminescent detection of fluoroquinolone antibiotics.

The development and characterization of novel, molecularly imprinted polymer nanofilament-based optical sensors for the analysis of enrofloxacin, an antibiotic widely used for human and veterinary applications, is reported. The polymers were prepared by nanomolding in porous alumina by using enrofloxacin as the template. The antibiotic was covalently immobilized on to the pore walls of the alumina by using different spacers, and the prepolymerization mixture was cast in the pores and the polymer synthesized anchored onto a glass support through UV polymerization. Various parameters affecting polymer selectivity were evaluated to achieve optimal recognition, namely, the spacer arm length and the binding solvent. The results of morphological characterization, binding kinetics, and selectivity of the optimized polymer material for ENR and its derivatives are reported. For sensing purposes, the nanofilaments were incubated in solutions of the target molecule in acetonitrile/HEPES buffer (100 mM, pH 7.5, 50:50, v/v) for 20 min followed by incubation in a 10 mM solution of europium(III) ions to generate a europium(III)-enrofloxacin complex on the polymer surface. The detection event was based on the luminescence of the rare-earth ion (λexc=340 nm; λem=612 nm) that results from energy transfer from the antibiotic excited state to the metal-ion emitting excited state. The limit of detection of the enrofloxacin antibiotic was found to be 0.58 µM.

Physical forms of MIPs.

The current state of the art in the development of methodologies for the preparation of MIPs in predetermined physical forms is critically reviewed, with particular attention being paid to the forms most widely employed in practical applications, such as spherical beads in the micro- to nanometer range, microgels, monoliths, membranes. Although applications of the various MIP physical forms are mentioned, the focus of the paper is mainly on the description of the various preparative methods. The aim is to provide the reader with an overview of the latest achievements in the field, as well as with a mean for critically evaluating the various proposed methodologies towards an envisaged application. The review covers the literature up to early 2010, with special emphasis on the developments of the last 10 years.

Patterning nanostructured, synthetic, polymeric receptors by simultaneous projection photolithography, nanomolding, and molecular imprinting.

Microscope projection photolithography is combined with nanomolding and molecular imprinting for the fast microfabrication of molecularly imprinted polymer (MIP) arrays in the form of micrometric islands of nanofilaments. Dot diameters from 70-90 µm are easily obtained using a 10× objective and a photomask carrying the desired pattern. The dots are composed of parallel nanofilaments of a high aspect ratio, 150 nm in diameter and several micrometers in length, which are obtained through a nanomolding procedure on porous alumina. The arrays are molecularly imprinted with the small molecule fluorescein or with the protein myoglobin. The fluorescein MIP arrays are able to specifically recognize their target, as demonstrated by fluorescence microscopy. A four-fold increase in binding capacity and imprinting factor (IF = 13) is obtained compared to non-nanostructured porous dots. Imprinting of the nanofilament arrays with the protein myoglobin as the template is also possible and allows for a high imprinting factor of 4.3. Such nanostructured microarrays of synthetic receptors obtained by projection photolithography have great potential in biosensor and biochip development.