Thiophilic paramagnetic particles as a batch separation medium for the purification of antibodies from various source materials

Removal of heavy metal ions with magnetic carbon prepared from corncob biomass

Four novel magnetic-activated carbons (MACs) were prepared, characterised, and used as adsorbents to remove heavy metal ions from wastewater samples. The MACs prepared, are advanced adsorbents for the removal of Hg(II), Cr(III), Cd(II), and Pb(II). The nature of the acid, amount, composition of the MACs, and the remotion time were evaluated in aqueous solutions. The ions removal percentages obtained, under the best conditions, were 93% for Hg(II) and higher than 99% for Pb(II), Cr(III), and Cd(II) (100 mg L-1, initial concentration in solution), with 100 mg of the MAC-3 in HNO3 3 mM. The capacity of the best adsorbent, MAC-3, for removing heavy metals ions Hg(II), Cr(III), Cd(II), and Pb(II) was studied using Langmuir and Freundlich adsorption isotherms under the best condition. The maximum adsorption capacities of Hg(II), Cr(III), Cd(II), and Pb(II) were found to be 10.72, 11.51, 11.49 and 11.49 mg g-1, the values of constants of Freundlich models were 17.98, 26.83, 9.18, and 7.18 mg g-1 respectively. For Hg(II) and Pb(II) the correlation factor (R2) was better for Freundlich model, while Cr(III) and Cd(II) showed better R2 with Langmuir model. Finally, the treatment for the elimination of heavy metal ions was carried out, with wastewater samples of industrial and domestic origin, and used for crop irrigation. The samples were collected in Irrigation District 003, Hidalgo, Mexico. The MAC-3 removes heavy metal ions from the wastewater matrix above 99%.

Catalytic Gold-Iridium Nanoparticles as Labels for Sensitive Colorimetric Lateral Flow Assay

The colorimetric lateral flow assay (CLFA, also known as test strip) is a widely used point-of-care diagnostic technology. It has been a challenge to significantly improve the detection sensitivity of CLFA without involving additional equipment and/or compromising its simplicity. In this work, we break through the detection limit barrier of CLFA by developing a type of catalytic nanoparticles (NPs) used as labels. Specifically, the NPs were engineered by coating conventional gold NPs (AuNPs) with iridium (Ir) to form an Au-Ir core-shell structure. Such Au-Ir NPs possess ultrahigh peroxidase-like catalytic activities. A single Au-Ir NP can generate up to 10⁷ colored molecules per second by catalyzing peroxidase substrates. The strong color signal from the catalysis ensures a high sensitivity of associated CLFA. The Au-Ir NP-based CLFA was successfully applied to the detection of two different cancer biomarkers that achieved limits of detection at the low picogram per milliliter level, hundreds of times lower than those of conventional AuNP-based CLFA.

pSBMA-Conjugated Magnetic Nanoparticles for Selective IgG Separation

Two types of zwitterionic polymer-modified magnetic nanoparticles (NPs) are fabricated by conjugating pSBMA onto PEI-precoated NPs via either a one-step method (1S NPs) or two-step method (2S NPs). For both methods, divinyl sulfone is used as the linker molecule. Although 1S NPs were capable of resisting both IgG and BSA, 2S NPs exhibited specificity toward IgG adsorption in complex biological fluids, e.g., in a mixture of serums and IgG. The moderate interactions ( K_d ≈ 1.2 μM) between IgG and 2S NPs are 3 orders of magnitude lower than IgG binding with protein A ( K_d 10 nM). Through complementary characterizations and analyses, we rationalize that the surface developed herein with IgG specificity contains two key components: polyzwitterions with a short chain length and sulfone groups with a high density.

Dextran-coated magnetic supports modified with a biomimetic ligand for IgG purification

Dextran-coated iron oxide magnetic particles modified with ligand 22/8, a protein A mimetic ligand, were prepared and assessed for IgG purification. Dextran was chosen as the agent to modify the surface of magnetic particles by presenting a negligible level of nonspecific adsorption. For the functionalization of the particles with the affinity ligand toward antibodies, three methods have been explored. The optimum coupling method yielded a theoretical maximum capacity for human IgG calculated as 568 ± 33 mg/g and a binding affinity constant of 7.7 × 10⁴ M⁻¹. Regeneration, recycle and reuse of particles was also highly successful for five cycles with minor loss of capacity. Moreover, this support presented specificity and effectiveness for IgG adsorption and elution at pH 11 directly from crude extracts with a final purity of 95% in the eluted fraction.

A biotechnological perspective on the application of iron oxide magnetic colloids modified with polysaccharides

Iron oxide magnetic nanoparticles (MNPs) alone are suitable for a broad spectrum of applications, but the low stability and heterogeneous size distribution in aqueous medium represent major setbacks. These setbacks can however be reduced or diminished through the coating of MNPs with various polymers, especially biopolymers such as polysaccharides. Polysaccharides are biocompatible, non-toxic and renewable; in addition, they possess chemical groups that permit further functionalization of the MNPs. Multifunctional entities can be created through decoration with specific molecules e.g. proteins, peptides, drugs, antibodies, biomimetic ligands, transfection agents, cells, and other ligands. This development opens a whole range of applications for iron oxide nanoparticles. In this review the properties of magnetic structures composed of MNPs and several polysaccharides (Agarose, Alginate, Carrageenan, Chitosan, Dextran, Heparin, Gum Arabic, Pullulan and Starch) will be discussed, in view of their recent and future biomedical and biotechnological applications.

Interaction of pepsin with aromatic amino acids and their derivatives immobilized to Sepharose

The interaction of porcine pepsin A with immobilized derivatives of aromatic amino acids was investigated. Divinyl sulfone-activated Sepharose was used to immobilize N-acetyl-l-phenylalanine and 3,5-diiodo-l-tyrosine via their free carboxyl groups and l-tyrosine via its amino group. Immobilized l-tyrosine was iodinated after coupling. The optimum conditions for the separation of porcine pepsin A using the prepared affinity carriers were studied and the following parameters were established: enzyme recovery, reproducibility of analyses, capacity and dependence of the elution peak area on the concentration of the loaded enzyme. The ability of the prepared affinity carriers to retain various types of proteins was compared under optimum conditions for porcine pepsin A separation. While immobilized 3,5-diiodo-l-tyrosine and iodinated l-tyrosine-Sepharose adsorbed relatively high amounts of bovine serum albumin and ovalbumin, only negligible amounts of these proteins were adsorbed to immobilized N-acetyl-l-phenylalanine. The behavior of porcine pepsin A was the same as its complex with pepstatin A on the prepared affinity carriers, indicating that the enzyme active site is not involved in the studied interaction.