Encapsulation of sugar beet phytoglobin BvPgb 1.2 and myoglobin in a lipid sponge phase system

Globins are usually associated with oxygen carriage in vertebrates. However, plants also contain similar heme-containing proteins, called phytoglobins (Pgbs). Unlike conventional hemoglobin, these proteins are often linked to nitric oxide metabolism, energy metabolism and redox maintenance under hypoxic and related abiotic and biotic stress conditions. Class I and II non-symbiotic Pgbs (nsPgbs) have different degrees of heme hexacoordination. This involves direct interaction of the distal histidine in the E-helix with the sixth coordination site of the central iron, resulting in increased stability, in contrast to the oxygen storage linked to pentacoordinated globins, such as myoglobin (Mb). Due to their robustness, nsPgbs have substantial potential for various biomedical applications, particularly for iron supplementation. In this study, a class I nsPgb from sugar beet (Beta vulgaris ssp. vulgaris) was encapsulated in a lipid sponge phase system for potential protein delivery purposes and compared to a similar system of Mb containing nanoparticles. Bulk phases and dispersions were made with two lipid compositions (30/45/25 diglycerol monooleate (DGMO)/Capmul GMO-50/sorbitan monooleate (P80) and 28/42/30 DGMO/GMO-50/P80, where the DGMO/GMO-50 ratio was kept constant at 40/60). In addition, buffer effects on protein loading and particle formation were investigated. High concentrations of BvPgb1.2 (60 mg/mL) showed higher aggregation tendencies than Mb but these appeared to be transient. This property could be coupled to the higher isoelectric point (pI) of the BvPgb1.2 (7.85, compared to 6.8 for Mb), which make it more sensitive to small pH changes. In addition, excess protein/leakage was observed with Mb from the nanoparticles when analysed with size exclusion chromatography. This work highlighted the encapsulation efficiency of these proteins, which might be directly linked to difference in iron coordination and therefore, reactivity and lipid peroxidation. The interactions between the bulk phases and dispersion of the hemeproteins are complex, more research is needed to proper elucidate these relations in more detail, in order to facilitate the encapsulation capacity for heme-containing proteins in similar lipid-based systems

Chromatographic separation of hemoglobin variants using robust molecularly imprinted polymers

Devising a robust, efficient and cost effective hemoglobin (Hb) purification strategy is one of the key challenges in the development of Hb-based blood substitutes. The aim of this study was to use molecularly imprinted polymers (MIPs) as a novel and efficient chromatographic resin to selectively recognize and purify different Hb variants. The results showed that the Hb-MIP material developed here could selectively recognize and purify various Hb directly from either crude E. coli extracts or human body fluids, such as blood plasma and cerebrospinal fluid (CSF), in one-step. The dynamic binding capacity at 10% breakthrough was around 7.4 mg mL−1resin for adult Hb (HbA) and fetal Hb (HbF). This chromatographic material also allowed identification of changes related to amino acid substitutions on the Hb protein surface. For instance, when an additional lysine residue was introduced, the HbA αY42K mutant eluted later in an Hb-MIP column than wildtype HbA. Additional negative charges on the protein surface, such as aspartate, mitigated the interaction between the protein and imprinted polymers, and therefore an αA19D-αA12D HbF mutant eluted earlier, at −2.7 column volumes compared to wildtype HbF

Ag−Polymer nanocomposites for capture, detection, and destruction of bacteria

Bacterial infection is one of the major problems for human health. To prevent outbreak of bacteria-caused diseases, early diagnosis of bacterial pathogen and effective destruction of pathogenic microorganisms are in urgent need. In this work, we developed a new multifunctional nanocomposite material that can effectively capture and destroy bacteria. Epoxide-modified nanoparticles were synthesized by microemulsion polymerization and precipitation polymerization. The epoxide groups on the particle surface were reacted with polyethylenimine to introduce cationic amine groups. The amine groups on the nanoparticle surface enhanced the colloidal stability of the particles’ suspension and provided multivalent interactions to bind and destroy the bacteria. After further modification with Ag nanoparticles, the final composite nanomaterial was able to not only capture and destroy Gram-negative bacteria but also allow the bacteria’s fingerprint spectra to be obtained through surface-enhanced Raman scattering.The multifunctional nanoparticles developed in this work offer a new approach toward fast capture, detection, and destruction of pathogenic bacteria

Plasmid DNA partitioning and separation using poly(ethylene glycol)/poly(acrylate)/salt aqueous two-phase systems

Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coil can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coil homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60-70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH. (C) 2012 Elsevier B.V. All rights reserved