Superporous agarose beads as a hydrophobic interaction chromatography support

Exploring the effects of resin particle sizes on enhancing antibody binding capacity of a hybrid biomimetic ligand

Particle size is a critical parameter of chromatographic resins that significantly affects protein separation. In this study, effects of resin particle sizes (31.26 μm, 59.85 μm and 85.22 μm named Aga-31, Aga-60 and Aga-85, respectively) on antibody adsorption capacity and separation performance of a hybrid biomimetic ligand were evaluated. Their performance was investigated through static adsorption and breakthrough assays to quantify static and dynamic binding capacity (Qmax and DBC). The static adsorption results revealed that the Qmax for hIgG was 152 mg/g resin with Aga-31, 151 mg/g resin with Aga-60, and 125 mg/g resin with Aga-85. Moreover, the DBC at 10% breakthrough for hIgG with a residence time of 2 min was determined to be 49.4 mg/mL for Aga-31, 45.9 mg/mL for Aga-60, and 38.9 mg/mL for Aga-85. The resins with smaller particle sizes exhibited significantly higher capacity compared to typical commercial agarose resins and a Protein A resin (MabSelect SuRe). Furthermore, the Aga-31 resin with the hybrid biomimetic ligand demonstrated exceptional performance in terms of IgG purity (>98%) and recovery (>96%) after undergoing 20 separation cycles from CHO cell supernatant. These findings are helpful in further chromatographic resin design for the industrial application of antibody separation and purification.

Extraction, Modification and Biomedical Application of Agarose Hydrogels: A Review

Numerous compounds present in the ocean are contributing to the development of the biomedical field. Agarose, a polysaccharide derived from marine red algae, plays a vital role in biomedical applications because of its reversible temperature-sensitive gelling behavior, excellent mechanical properties, and high biological activity. Natural agarose hydrogel has a single structural composition that prevents it from adapting to complex biological environments. Therefore, agarose can be developed into different forms through physical, biological, and chemical modifications, enabling it to perform optimally in different environments. Agarose biomaterials are being increasingly used for isolation, purification, drug delivery, and tissue engineering, but most are still far from clinical approval. This review classifies and discusses the preparation, modification, and biomedical applications of agarose, focusing on its applications in isolation and purification, wound dressings, drug delivery, tissue engineering, and 3D printing. In addition, it attempts to address the opportunities and challenges associated with the future development of agarose-based biomaterials in the biomedical field. It should help to rationalize the selection of the most suitable functionalized agarose hydrogels for specific applications in the biomedical industry.

Separation and characterization of microplastic and nanoplastic particles in marine environment

Microplastics (<5 mm) are divided into primary and secondary microplastics, which are further degraded into nanoplastics. The microplastic particles are widely distributed in marine environment, terrestrial ecosystem and biological organism, leading to damages to whole environmental system. Microplastics are not only difficult to degrade, but also able to adsorb pollutants. Due to the tiny size and various properties, the separation and characterization of microplastic particles has become more and more challenging. This review introduces the sources and destinations of the microplastic particles and summarizes the general methods for the sorting and characterization of microplastics, especially the manipulation of microplastic particles on microfluidic chip, showing possibility to deal with smaller nanoplastic particles over traditional methods. This review focuses on studies of the size-based separation and property-dependent characterization of microplastics in marine environment by utilizing the microfluidic chip device.

Polysaccharides as separation media for the separation of proteins, peptides and stereoisomers of amino acids

Reliable separation of peptides, amino acids and proteins as accurate as possible with the maximum conformation and biological activity is crucial and essential for drug discovery. Polysaccharide, as one of the most abundant natural biopolymers with optical activity on earth, is easy to be functionalized due to lots of hydroxyl groups on glucose units. Over the last few decades, polysaccharide derivatives are gradually employed as effective separation media. The highly-ordered helical structure contributes to complex, diverse molecular recognition ability, allowing polysaccharide derivatives to selectively interact with different analytes. This article reviews the development, application and prospects of polysaccharides as separation media in the separation of proteins, peptides and amino acids in recent years. The chiral molecules mechanism, advantages, limitations, development status and challenges faced by polysaccharides as separation media in molecular recognition are summarized. Meanwhile, the direction of its continued development and future prospects are also discussed.

Superporous agarose scaffolds for encapsulation of adult human islets and human stem-cell-derived β cells for intravascular bioartificial pancreas applications

Type 1 diabetic patients with severe hypoglycemia unawareness have benefitted from cellular therapies, such as pancreas or islet transplantation; however, donor shortage and the need for immunosuppression limits widespread clinical application. We previously developed an intravascular bioartificial pancreas (iBAP) using silicon nanopore membranes (SNM) for immunoprotection. To ensure ample nutrient delivery, the iBAP will need a cell scaffold with high hydraulic permeability to provide mechanical support and maintain islet viability and function. Here, we examine the feasibility of superporous agarose (SPA) as a potential cell scaffold in the iBAP. SPA exhibits 66-fold greater hydraulic permeability than the SNM along with a short (<10 μm) diffusion distance to the nearest islet. SPA also supports short-term functionality of both encapsulated human islets and stem-cell-derived enriched β-clusters in a convection-based system, demonstrated by high viability (>95%) and biphasic insulin responses to dynamic glucose stimulus. These findings suggest that the SPA scaffold will not limit nutrient delivery in a convection-based bioartificial pancreas and merits continued investigation.

A color turn-on fluorescent probe for real-time detection of hydrogen sulfide and identification of food spoilage

A color and fluorescence turn-on H2S probe is synthesized, achieving real-time detection of H2S in pure water solution with high selectivity. Importantly, the probe is able to sense H2S gas in air via the probe-deposited test paper, which has been successfully used for food spoilage identification.

Dilemma on plasmid DNA purification: binding capacity vs selectivity

Plasmid DNA chromatography is a powerful field in constant development and evolution. The use of this technique is considered mandatory in the production of an efficient and safe formulation to be applied for plasmid-mediated gene therapy. Concerning this, the search for an ideal chromatographic support/ligand combination motivated scientist to pursue a continuous improvement on the plasmid chromatography performance, looking for a progression on the ligands and supports used. The present review explores the different approaches used over time to purify plasmid DNA, ambitioning both high recovery and high purity levels. Overall, it is presented a critical discussion relying on the relevance of the binding capacity versus selectivity of the supports.

Sensors that Learn: The Evolution from Taste Fingerprints to Patterns of Early Disease Detection

The McDevitt group has sustained efforts to develop a programmable sensing platform that offers advanced, multiplexed/multiclass chem-/bio-detection capabilities. This scalable chip-based platform has been optimized to service real-world biological specimens and validated for analytical performance. Fashioned as a sensor that learns, the platform can host new content for the application at hand. Identification of biomarker-based fingerprints from complex mixtures has a direct linkage to e-nose and e-tongue research. Recently, we have moved to the point of big data acquisition alongside the linkage to machine learning and artificial intelligence. Here, exciting opportunities are afforded by multiparameter sensing that mimics the sense of taste, overcoming the limitations of salty, sweet, sour, bitter, and glutamate sensing and moving into fingerprints of health and wellness. This article summarizes developments related to the electronic taste chip system evolving into a platform that digitizes biology and affords clinical decision support tools. A dynamic body of literature and key review articles that have contributed to the shaping of these activities are also highlighted. This fully integrated sensor promises more rapid transition of biomarker panels into wide-spread clinical practice yielding valuable new insights into health diagnostics, benefiting early disease detection.

Separation and Analysis of Microplastics and Nanoplastics in Complex Environmental Samples

The vast amount of plastic waste emitted into the environment and the increasing concern of potential harm to wildlife has made microplastic and nanoplastic pollution a growing environmental concern. Plastic pollution has the potential to cause both physical and chemical harm to wildlife directly or via sorption, concentration, and transfer of other environmental contaminants to the wildlife that ingest plastic. Small particles of plastic pollution, termed microplastics (>100 nm and <5 mm) or nanoplastics (<100 nm), can form through fragmentation of larger pieces of plastic. These small particles are especially concerning because of their high specific surface area for sorption of contaminants as well as their potential to translocate in the bodies of organisms. These same small particles are challenging to separate and identify in environmental samples because their size makes handling and observation difficult. As a result, our understanding of the environmental prevalence of nanoplastics and microplastics is limited. Generally, the smaller the size of the plastic particle, the more difficult it is to separate from environmental samples. Currently employed passive density and size separation techniques to isolate plastics from environmental samples are not well suited to separate microplastics and nanoplastics. Passive flotation is hindered by the low buoyancy of small particles as well as the difficulty of handling small particles on the surface of flotation media. Here we suggest exploring alternative techniques borrowed from other fields of research to improve separation of the smallest plastic particles. These techniques include adapting active density separation (centrifugation) from cell biology and taking advantage of surface-interaction-based separations from analytical chemistry. Furthermore, plastic pollution is often challenging to quantify in complex matrices such as biological tissues and wastewater. Biological and wastewater samples are important matrices that represent key points in the fate and sources of plastic pollution, respectively. In both kinds of samples, protocols need to be optimized to increase throughput, reduce contamination potential, and avoid destruction of plastics during sample processing. To this end, we recommend adapting digestion protocols to match the expected composition of the nonplastic material as well as taking measures to reduce and account for contamination. Once separated, plastics in an environmental sample should ideally be characterized both visually and chemically. With existing techniques, microplastics and nanoplastics are difficult to characterize or even detect. Their low mass and small size provide limited signal for visual, vibrational spectroscopic, and mass spectrometric analyses. Each of these techniques involves trade-offs in throughput, spatial resolution, and sensitivity. To accurately identify and completely quantify microplastics and nanoplastics in environmental samples, multiple analytical techniques applied in tandem are likely to be required.

Enhancement of performance in porous bead-based microchip sensors: Effects of chip geometry on bio-agent capture

Measuring low concentrations of clinically-important biomarkers using porous bead-based lab-on-a-chip (LOC) platforms is critical for the successful implementation of point-of-care (POC) devices. One way to meet this objective is to optimize the geometry of the bead holder, referred to here as a micro-container. In this work, two geometric micro-containers were explored, the inverted pyramid frustum (PF) and the inverted clipped pyramid frustum (CPF). Finite element models of this bead array assay system were developed to optimize the micro-container and bead geometries for increased pressure, to increase analyte capture in porous bead-based fluorescence immunoassays. Custom micro-milled micro-container structures containing an inverted CPF geometry resulted in a 28% reduction in flow-through regions from traditional anisotropically-etched pyramidal geometry derived from Si-111 termination layers. This novel "reduced flow-through" design resulted in a 33% increase in analyte penetration into the bead and twofold increase in fluorescence signal intensity as demonstrated with C-Reactive Protein (CRP) antigen, an important biomarker of inflammation. A consequent twofold decrease in the limit of detection (LOD) and the limit of quantification (LOQ) of a proof-of-concept assay for the free isoform of Prostate-Specific Antigen (free PSA), an important biomarker for prostate cancer detection, is also presented. Furthermore, a 53% decrease in the bead diameter is shown to result in a 160% increase in pressure and 2.5-fold increase in signal, as estimated by COMSOL models and confirmed experimentally by epi-fluorescence microscopy. Such optimizations of the bead micro-container and bead geometries have the potential to significantly reduce the LODs and reagent costs for spatially programmed bead-based assay systems of this type.

Porous bead-based diagnostic platforms: bridging the gaps in healthcare

Advances in lab-on-a-chip systems have strong potential for multiplexed detection of a wide range of analytes with reduced sample and reagent volume; lower costs and shorter analysis times. The completion of high-fidelity multiplexed and multiclass assays remains a challenge for the medical microdevice field; as it struggles to achieve and expand upon at the point-of-care the quality of results that are achieved now routinely in remote laboratory settings. This review article serves to explore for the first time the key intersection of multiplexed bead-based detection systems with integrated microfluidic structures alongside porous capture elements together with biomarker validation studies. These strategically important elements are evaluated here in the context of platform generation as suitable for near-patient testing. Essential issues related to the scalability of these modular sensor ensembles are explored as are attempts to move such multiplexed and multiclass platforms into large-scale clinical trials. Recent efforts in these bead sensors have shown advantages over planar microarrays in terms of their capacity to generate multiplexed test results with shorter analysis times. Through high surface-to-volume ratios and encoding capabilities; porous bead-based ensembles; when combined with microfluidic elements; allow for high-throughput testing for enzymatic assays; general chemistries; protein; antibody and oligonucleotide applications.

Organic monoliths for hydrophilic interaction electrochromatography/chromatography and immunoaffinity chromatography

This article is aimed at providing a review of the progress made over the past decade in the preparation of polar monoliths for hydrophilic interaction LC (HILIC)/capillary electrochromatography (HI-CEC) and in the design of immuno-monoliths for immunoaffinity chromatography that are based on some of the polar monolith precursors used in HILIC/HI-CEC. In addition, this review article discusses some of the applications of polar monoliths by HILIC and HI-CEC, and the applications of immuno-monoliths. This article is by no means an exhaustive review of the literature; it is rather a survey of the recent progress made in the field with 83 references published in the past decade on the topics of HILIC and immunoaffinity chromatography monoliths.

Programmable nano-bio-chips: multifunctional clinical tools for use at the point-of-care

A new generation of programmable diagnostic devices is needed to take advantage of information generated from the study of genomics, proteomics, metabolomics and glycomics. This report describes the 'programmable nano-bio-chip' with potential to bridge the significant scientific, technology and clinical gaps through the creation of a diagnostic platform to measure the molecules of life. This approach, with results at the point-of-care, possesses capabilities for measuring such diverse analyte classes as cells, proteins, DNA and small molecules in the same compact device. Applications such as disease diagnosis and prognosis for areas including cancer, heart disease and HIV are described. New diagnostic panels are inserted as 'plug and play' elements into the modular platform with universal assay operating systems and standard read out sequences. The nano-bio-chip ensemble exhibits excellent analytical performance and cost-effectiveness with extensive validation versus standard reference methods (R(2) = 0.95-0.99). This report describes the construction and use of two major classes of nano-bio-chip designs that serve as cellular and chemical processing units, and provides perspective on future growth in this newly emerging field of programmable nano-bio-chip sensor systems.

A microchip-based assay for interleukin-6

The electronic taste chip (ETC) assay system is a lab-on-a-chip technology that offers a microchip platform on which bead-based immunoassays are performed. Each bead within the array serves as its own independent self-contained "microreactor" system, with its selectivity determined by the specificity of the antibody that it hosts. The bead-loaded chip is sandwiched between two optically transparent polymethylmethacrylate inserts, packaged within a metal casing described here as the "flow cell." This flow cell allows for delivery of sample and detecting reagents to the microchip and the associated beads. Images of fluorescent beads are captured with a digital video chip and analyzed to facilitate detection and, ultimately, quantitation of analytes in complex fluids. This chapter describes the application of the ETC system for the detection and measurement of interleukin (IL)-6.

Superporous agarose anion exchangers for plasmid isolation

Superporous agarose beads have wide, connecting flow pores allowing large molecules such as plasmids to be transported into the interior of the beads by convective flow. The pore walls provide additional surface for plasmid binding thus increasing the binding capacity of the adsorbent. Novel superporous agarose anion exchangers have been prepared, differing with respect to bead diameter, superpore diameter and type of anion-exchange functional group (poly(ethyleneimine) and quaternary amine). The plasmid binding capacities were obtained from breakthrough curves and compared with the binding capacity of homogeneous agarose beads of the same particle size. Significantly, the smaller diameter superporous agarose beads were found to have four to five times higher plasmid binding capacity than the corresponding homogeneous agarose beads. The experimentally determined plasmid binding capacity was compared with the theoretically calculated surface area for each adsorbent and fair agreement was found. Confocal microscopy studies of beads with adsorbed, fluorescently labelled plasmids aided in the interpretation of the results. Superporous poly(ethyleneimine)-substituted beads with a high ion capacity (230 micromol/ml) showed a plasmid binding of 3-4 mg/ml adsorbent. Superporous quaternary amine-substituted beads had a lower ion capacity (81 micromol/ml) and showed a correspondingly lower plasmid binding capacity (1-2 mg/ml adsorbent). In spite of the lower capacity, the beads with quaternary amine ligand were preferred, due to their much better plasmid recovery (70-100% recovery). Interestingly, both capacity and recovery was improved when the plasmid adsorption step was carried out in the presence of a moderate salt concentration. The most suitable superporous bead type (45-75 microm diameter beads; 4 microm superpores; quaternary amine ligand) was chosen for the capture of plasmid DNA from a clarified alkaline lysate. Two strategies were evaluated, one with and one without enzymatic digestion of RNA. The strategy without RNase gave high plasmid recovery, quantitative removal of protein and a 70% reduction in RNA.

Affinity monolith chromatography

The combined use of monolithic supports with selective affinity ligands as stationary phases has recently given rise to a new method known as affinity monolith chromatography (AMC). This review will discuss the basic principles behind AMC and examine the types of supports and ligands that have been employed in this method. Approaches for placing affinity ligands in monoliths will be considered, including methods based on covalent immobilization, biospecific adsorption, entrapment, and the formation of coordination complexes. Several reported applications will then be presented, such as the use of AMC for bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, dye-ligand affinity chromatography, and biomimetic chromatography. Other applications that will be discussed are chiral separations and studies of biological interactions based on AMC.

A novel superporous agarose medium for high-speed protein chromatography

A novel superporous agarose (SA) bead characterized by the presence of wide pores has been fabricated by water-in-oil emulsification using solid granules of calcium carbonate as porogenic agent. After cross-linking, the solid granules were removed by dissolving them in hydrochloric acid. Then, the gel was modified with diethylaminoethyl groups to create an anion exchanger, SA-DEAE, for protein adsorption. A homogeneous agarose (HA) bead was also produced and modified with DEAE for comparison. It was found that the porosity of SA-DEAE was about 6% larger than that of HA-DEAE. Moreover, both optical micrographs and confocal laser scanning microscopy (CLSM) of the ion exchangers with adsorbed fluorescein isothiocyanate (FITC) labeled IgG revealed the superporous structure of the SA medium. In addition, the SA-DEAE column had lower backpressure than the HA-DEAE column, confirming the convective flow of mobile phase through the wide pores. Due to the presence of the wide pores, more channels were available for protein transport and, furthermore, more diffusive pores in the agarose network were accessible for the protein approach from different directions. This led to 40% higher protein capacity and two times higher effective pore diffusivity in the SA-DEAE than in HA-DEAE. Moreover, an increase of the efficiency of the SA-DEAE column until a flow rate of 5 cm/min and the independency of the column efficiency at flow rates from 5 to 17.8 cm/min was found, indicating that intraparticle mass transfer was intensified by convective flow at elevated flow rates. Therefore, the chromatographic resolution of IgG and BSA was little affected up to a flow rate of 17.8 cm/min. The results indicate that the SA medium is favorable for high-speed protein chromatography.

Improved lectin-mediated immobilization of human red blood cells in superporous agarose beads

A new type of agarose bead, superporous agarose, was used as a gel support for immobilization of human red blood cells (RBCs) mediated by wheat germ lectin. The number of immobilized cells was similar to that obtained with commercial wheat germ lectin-agarose but the cell stability appeared to be superior. This allowed improved frontal affinity chromatographic analyses of cytochalasin B (CB)-binding to the glucose transporter GLUT1 which established a ratio of one CB-binding site per GLUT1 dimer for both plain RBCs or those treated with different poly amino acids. The measured dissociation constants, 70+/-14 nM for CB and 12+/-3 mM for glucose binding to GLUT1, are similar to those reported earlier.

Hydrophobic interaction chromatography of proteins

In this article, an overview of hydrophobic interaction chromatography (HIC) of proteins is given. After a brief description of protein hydrophobicity and hydrophobic interactions, we present the different proposed theories for the retention mechanism of proteins in HIC. Additionally, the main parameters to consider for the optimization of fractionation processes by HIC and the stationary phases available were described. Selected examples of protein fractionation by HIC are also presented.

Poly(glycidyl methacrylate-divinylbenzene-triallylisocyanurate) continuous-bed protein chromatography

A novel continuous bed with high dynamic adsorption capacity for protein has been developed. It is a macroporous poly(glycidyl methacrylate-divinylbenzene-triallylisocyanurate) rod prepared by in situ copolymerization in a chromatographic tube. The bed matrix contained epoxy groups, so diethylaminohydroxypropyl groups were coupled to the matrix, leading to an anion-exchange continuous bed. The component, specific surface area, and the pore structure of the bed matrix were characterized by Fourier transform infrared spectroscopy, BET method and scanning and transmission electron microscopies, respectively. The flow properties, column efficiency and the dynamic adsorption behavior of the bed were studied. The results show that the continuous bed, a ternary copolymer of glycidyl methacrylate (GMA), divinylbenzene (DVB) and triallylisocyanurate (TAIC) with a specific surface area of 56.4 m2/g, consisted of a three-dimensional structure made up of continuous clusters of microspheres (300 nm) and interconnected irregular pores. The rate of mass transfer is enhanced by the convection of the mobile phase through the pores. The dynamic adsorption isotherm of the anion-exchange column for bovine serum albumin was expressed by the Langmuir equation with a dynamic capacity as high as 76.0 mg/g. Moreover, the separation of proteins, i.e. lysozyme, hemoglobin and bovine serum albumin, is little affected by mobile-phase velocity up to 902.5 cm/h; it was completed within 5 min at 902.5 cm/h.

Continuous superporous agarose beds for chromatography and electrophoresis

Continuous agarose beds (monoliths) were prepared by casting agarose emulsions designed to generate superporous agarose. The gel structures obtained were transected by superpores (diameters could be varied in the range 20-200 microns) through which liquids could be pumped. The pore structure and the basic properties of the continuous gel were investigated by microscopy and size exclusion chromatography. The chromatographic behaviour was approximately the same as for beds packed with homogeneous agarose beads with a particle diameter equivalent to the distance between the superpores. In one application, the superporous continuous agarose bed was derivatized with a NAD+ analogue and used in the affinity purification of bovine lactate dehydrogenase from a crude extract. In another application, a new superporous composite gel material was prepared by adding hydroxyapatite particles to the agarose phase. The composite bed was used to separate a protein mixture by hydroxyapatite chromatography. In a third application, the continuous superporous agarose material was used as an electrophoresis gel. Here, a water-immiscible organic liquid was pumped through the superpores to dissipate the joule heat evolved, thus allowing high current densities.