Chromatography of microbial cells using continuous supermacroporous affinity and ion-exchange columns

Hybrid machine learning model based predictions for properties of poly(2-hydroxyethyl methacrylate)-poly(vinyl alcohol) composite cryogels embedded with bacterial cellulose

Supermacroporous composite cryogels with enhanced adjustable functionality have received extensive interest in bioseparation, tissue engineering, and drug delivery. However, the variations in their components significantly impactfinal properties. This study presents a two-step hybrid machine learning approach for predicting the properties of innovative poly(2-hydroxyethyl methacrylate)-poly(vinyl alcohol) composite cryogels embedded with bacterial cellulose (pHEMA-PVA-BC) based on their compositions. By considering the ratios of HEMA (1.0-22.0 wt%), PVA (0.2-4.0 wt%), poly(ethylene glycol) diacrylate (1.0-4.5 wt%), BC (0.1-1.5 wt%), and water (68.0-96.0 wt%) as investigational variables, overlay sampling uniform design (OSUD) was employed to construct a high-quality dataset for model development. The random forest (RF) model was used to classify the preparation conditions. Then four models of artificial neural network, RF, gradient boosted regression trees (GBRT), and XGBoost were developed to predict the basic properties of the composite cryogels. The results showed that the RF model achieved an accurate three-class classification of preparation conditions. Among the four models, the GBRT model exhibited the best predictive performance of the basic properties, with the mean absolute percentage error of 16.04 %, 0.85 %, and 2.44 % for permeability, effective porosity, and height of theoretical plate (1.0 cm/min), respectively. Characterization results of the representative pHEMA-PVA-BC composite cryogel showed an effective porosity of 81.01 %, a permeability of 1.20 × 10-12 m2, and a range of height of theoretical plate between 0.40-0.49 cm at flow velocities of 0.5-3.0 cm/min. These indicate that the pHEMA-PVA-BC cryogel was an excellent material with supermacropores, low flow resistance and high mass transfer efficiency. Furthermore, the model output demonstrates that the alteration of the proportions of PVA (0.2-3.5 wt%) and BC (0.1-1.5 wt%) components in composite cryogels resulted in significant changes in the material basic properties. This work represents an attempt to efficiently design and prepare target composite cryogels using machine learning and providing valuable insights for the efficient development of polymers.

Dimethylsulfoniopropionate decorated cryogels as synthetic spatially structured habitats of marine bacterial communities

In microbial consortia bacteria often settle on other organisms that provide nutrients and organic material for their growth. This is true for the plankton where microalgae perform photosynthesis and exude metabolites that feed associated bacteria. The investigation of such processes is difficult since algae provide bacteria with a spatially structured environment with a gradient of released organic material that is hard to mimic. Here we introduce the design and synthesis of a cryogel-based microstructured habitat for bacteria that provides dimethylsulfoniopropionate (DMSP) as a carbon and sulfur source for growth. DMSP, a widely distributed metabolite released by algae, is thereby made available for bacteria in a biomimetic manner. Based on a novel DMSP derived building block (DMSP-HEMA), we synthesized cryogels providing structured surfaces for settlement and delivering the organic material fueling bacterial growth. By monitoring bacterial settlement and performance we show that the cryogels represent microbial arenas mimicking the ecological situation in the plankton.

Lectin Purification through Affinity Chromatography Exploiting Macroporous Monolithic Adsorbents

Growing medical, engineering, biochemical, and biological interest has led to a steady pace of research and development into polymeric monolithic structures with densely interconnected pores for purifying bio compounds. Cryogels, which are generated by freezing a reactive polymerization mixture, are highlighted due to their versatility and low relative cost as macroporous, polymeric, monolithic adsorbents. The conversion of cryogels into affinity adsorbents is one possible alternative to their optimal application. Some of the most often utilized supports for immobilizing particular ligands are monolithic columns manufactured with epoxy radicals on their surfaces. The purification of biomolecules with a high degree of specificity, such as lectins and glycoproteins with an affinity for glycosylated groups, has garnered interest in the use of fixed non-traditional beds functionalized with ligands of particular interest. The interaction is both robust enough to permit the adsorption of glycoproteins and reversible enough to permit the dissociation of molecules in response to changes in the solution’s pH. When compared to other protein A-based approaches, this one has been shown to be more advantageous than its counterparts in terms of specificity, ease of use, and cost-effectiveness. Information on polymeric, macroporous, monolithic adsorbents used in the affinity chromatographic purification of lectins has been published and explored.

Adsorption and immobilization of β-glucosidase from Thermoascus aurantiacus on macroporous cryogel by hydrophobic interaction

Enzyme immobilization has been reported as a promising approach to improving parameters such as thermal stability, pH and reusability. In this study, a polyacrylamide cryogel functionalized with L-phenylalanine was prepared to be used in the adsorption of β-glucosidase from Thermoascus aurantiacus, aiming at its separation and also its immobilization on the cryogel matrix. The enzyme was produced by solid state fermentation. First, the adsorption was studied as a function of the pH and the resulting yield (Y, %) and purification factor (P_F, dimensionless) were determined (1.57-5.13 and 64.19-91.20, respectively). The P_F and yield from eluate samples obtained at pH 3.0 were the highest (5.13 and 91.20, respectively). Then, β-glucosidase was immobilized on the hydrophobic cryogel and the recovery activities (%) were determined as a function of temperature and in the presence of different saline solutions. The values ranged from 14.45 to 45.97. As expected, salt type and ionic strength affected the activity remained in the immobilized β-glucosidase. The average bioreactor activity was 39.9 U/g of dry cryogel and its operational stability was measured, with no decrease in activity being observed during seven cycles. Kinetic parameters of free and immobilized enzyme were determined according to different models.

Cell Chromatography: Biocompatible Chromatographic Separation and Interrogation of Microbial Cells

The isolation of pure, single colonies lies at the heart of experimental microbiology. However, a microbial colony typically contains around 1 million cells at all stages of the life cycle. Here, we describe a novel cell chromatography method that facilitates the capture, purification, and interrogation of microbial cell populations from both single and mixed cultures. The method described relies on, but is not limited to, differences in surface charge to separate bacterial strains. The method is fully biocompatible, leading to no significant loss of cell viability. The chromatographic capture of cells, combined with selective elution methods, facilitates a greater level of experimental control over the sample inputs required for downstream high-throughput and high-sensitivity analytical methods. The application of the method for interrogating the antibiotic resistance of bacterial strains and for the separation of bacteria from environmental samples is illustrated. IMPORTANCE This is the first report of a method for separating microbial cells using chromatography, with full retention of cell viability. Differences in the surface chemistry of microbial cells provides a means of attracting cells to immobilized microbeads. Some cells are attracted, and some are repelled. The differences in, for example, surface charge can be harnessed to capture, interrogate, and separate environmental samples, thus circumventing the need to use conventional bacterial plating methods. This method will greatly facilitate drug discovery and bioprospecting for novel microbial compounds.

Affinity monolith chromatography: A review of general principles and recent developments

Affinity monolith chromatography (AMC) is a liquid chromatographic technique that utilizes a monolithic support with a biological ligand or related binding agent to isolate, enrich, or detect a target analyte in a complex matrix. The target-specific interaction exhibited by the binding agents makes AMC attractive for the separation or detection of a wide range of compounds. This article will review the basic principles of AMC and recent developments in this field. The supports used in AMC will be discussed, including organic, inorganic, hybrid, carbohydrate, and cryogel monoliths. Schemes for attaching binding agents to these monoliths will be examined as well, such as covalent immobilization, biospecific adsorption, entrapment, molecular imprinting, and coordination methods. An overview will then be given of binding agents that have recently been used in AMC, along with their applications. These applications will include bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, and dye-ligand or biomimetic affinity chromatography. The use of AMC in chiral separations and biointeraction studies will also be discussed.

Bioengineering a cryogel-derived bioartificial liver using particle image velocimetry defined fluid dynamics

Bioartificial Liver (BAL) devices are extracorporeal systems designed to support or recover hepatic function in patients with liver failure. The design of an effective BAL remains an open challenge since it requires a complex co-optimisation of cell colonisation, biomaterial scaffold and BAL fluid dynamics. Building on previous evidence of suitability as a blood perfusion device for detoxification, the current study investigated the use of RGD-containing p(HEMA)-alginate cryogels as BAL scaffolds. Cryogels were modified with alginate to reduce protein fouling and functionalised with an RGD-containing peptide to increase hepatocyte adhesion. A novel approach for characterisation of the internal flow through the porous matrix was developed by employing Particle Image Velocimetry (PIV) to visualise flow inside cryogels. Based on PIV results, which showed the laminar nature of flow inside cryogel pores, a multi-layered bioreactor composed of spaced cryogel discs was designed to improve blood/hepatocyte mass exchange. The stacked bioreactor showed a significantly higher production of albumin and urea compared to the column version, with improved cell colonisation and proliferation over time. The cell-free cryogel-based device was tested for safety in a bile-duct ligation model of liver cirrhosis. Thus, a stacked bioreactor prototype was developed based on a surface-engineered cryogel design with optimised fluid dynamics for BAL use.

Cryostructuring of Polymeric Systems. 55. Retrospective View on the More than 40 Years of Studies Performed in the A.N.Nesmeyanov Institute of Organoelement Compounds with Respect of the Cryostructuring Processes in Polymeric Systems

The processes of cryostructuring in polymeric systems, the techniques of the preparation of diverse cryogels and cryostructurates, the physico-chemical mechanisms of their formation, and the applied potential of these advanced polymer materials are all of high scientific and practical interest in many countries. This review article describes and discusses the results of more than 40 years of studies in this field performed by the researchers from the A.N.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences-one of the key centers, where such investigations are carried out. The review includes brief historical information, the description of the main effects and trends characteristic of the cryostructuring processes, the data on the morphological specifics inherent in the polymeric cryogels and cryostructurates, and examples of their implementation for solving certain applied tasks.

Past, Present, and Future of Affinity-based Cell Separation Technologies

Progress in cell purification technology is critical to increase the availability of viable cells for therapeutic, diagnostic, and research applications. A variety of techniques are now available for cell separation, ranging from non-affinity methods such as density gradient centrifugation, dielectrophoresis, and filtration, to affinity methods such as chromatography, two-phase partitioning, and magnetic-/fluorescence-assisted cell sorting. For clinical and analytical procedures that require highly purified cells, the choice of cell purification method is crucial, since every method offers a different balance between yield, purity, and bioactivity of the cell product. For most applications, the requisite purity is only achievable through affinity methods, owing to the high target specificity that they grant. In this review, we discuss past and current methods for developing cell-targeting affinity ligands and their application in cell purification, along with the benefits and challenges associated with different purification formats. We further present new technologies, like stimuli-responsive ligands and parallelized microfluidic devices, towards improving the viability and throughput of cell products for tissue engineering and regenerative medicine. Our comparative analysis provides guidance in the multifarious landscape of cell separation techniques and highlights new technologies that are poised to play a key role in the future of cell purification in clinical settings and the biotech industry. STATEMENT OF SIGNIFICANCE: Technologies for cell purification have served science, medicine, and industrial biotechnology and biomanufacturing for decades. This review presents a comprehensive survey of this field by highlighting the scope and relevance of all known methods for cell isolation, old and new alike. The first section covers the main classes of target cells and compares traditional non-affinity and affinity-based purification techniques, focusing on established ligands and chromatographic formats. The second section presents an excursus of affinity-based pseudo-chromatographic and non-chromatographic technologies, especially focusing on magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). Finally, the third section presents an overview of new technologies and emerging trends, highlighting how the progress in chemical, material, and microfluidic sciences has opened new exciting avenues towards high-throughput and high-purity cell isolation processes. This review is designed to guide scientists and engineers in their choice of suitable cell purification techniques for research or bioprocessing needs.

Peroxidase Immobilized Cryogels for Phenolic Compounds Removal

In this presented work, preparation of poly(AAm) cryogel, peroxidase immobilization onto the poly(AAm) cryogel, and usability of these enzyme modified cryogels for phenolic compounds removal were described. For this purpose, poly(AAm) cryogels were synthesized by using cryocopolymerization technique at sub-zero temperatures, and covalently functionalized with peroxidase enzyme by EDC/NHS chemistry. Characterization of the cryogels was carried out by FTIR, SEM, and EDX analysis. Maximum peroxidase loading onto poly(AAm) cryogel was found to be as 127.30 mg/g cryogel. Kinetic parameters of free and immobilized peroxidases were also investigated along with the stability tests. Finally, phenolic compounds removal efficiency of the peroxidase immobilized poly(AAm) cryogel was studied towards model phenolics such as phenol, bisphenol A, guaiacol, pyrogallol, and catechol; and very high phenolic removal efficiency was recorded.

Supermacroporous Composite Cryogels in Biomedical Applications

Supermacroporous gels, called cryogels, are unique scaffolds that can be prepared by polymerization of monomer solution under sub-zero temperatures. They are widely used in many applications and have significant potential biomaterials, especially for biomedical applications due to their inherent interconnected supermacroporous structures and easy formation of composite polymers in comparison to other porous polymer synthesis techniques. This review highlights the fundamentals of supermacroporous cryogels and composite cryogels, and then comprehensively summarizes recent studies in preparation, functionalization, and utilization with mechanical, biological and physicochemical features, according to the biomedical applications. Furthermore, conclusions and outlooks are discussed for the use of these promising and durable supermacroporous composite cryogels.

Biomedical Applications of Polymeric Cryogels

The application of interconnected supermacroporous cryogels as support matrices for the purification, separation and immobilization of whole cells and different biological macromolecules has been well reported in literature. Cryogels have advantages over traditional gel carriers in the field of biochromatography and related biomedical applications. These matrices nearly mimic the three-dimensional structure of native tissue extracellular matrix. In addition, mechanical, osmotic and chemical stability of cryogels make them attractive polymeric materials for the construction of scaffolds in tissue engineering applications and in vitro cell culture, separation materials for many different processes such as immobilization of biomolecules, capturing of target molecules, and controlled drug delivery. The low mass transfer resistance of cryogel matrices makes them useful in chromatographic applications with the immobilization of different affinity ligands to these materials. Cryogels have been introduced as gel matrices prepared using partially frozen monomer or polymer solutions at temperature below zero. These materials can be produced with different shapes and are of interest in the therapeutic area. This review highlights the recent advances in cryogelation technologies by emphasizing their biomedical applications to supply an overview of their rising stars day to day.

Preparation and characterization of large-format macroporous cryogel disks for use in affinity chromatography and biotechnological applications

We have prepared and evaluated larger format phage-bound epoxy-cryogel columns in order to increase the yield of bound target. Freezing thermograms showed that larger column formats (2.5-5 cm diameter) are not usable due to irregular polymerization phenomena. Preparing thin disks of 0.5 cm height with similar diameter proved to be an excellent alternative. Disks could be stacked and run in a chromatographic setup. In this way, we could increase the matrix volume, ligand-binding capacity, and finally the yield of bound target. By increasing the column volume about sevenfold, we observed a 12-fold increase of ligand density and a sevenfold increase in the yield of protein recovery in a column where phages were attached without spacer and a 10- to 34-fold increase in a spacer column, depending on the spacer used.

Use of nicotinamide decorated polymeric cryogels as heavy metal sweeper

Cryogels are synthetic polymers used in adsorption experiments in recent years. Because of their macropores, they provide an excellent advantage as an adsorbent in continuous and batch adsorption processes. In this study, nicotinamide (NAA) decorated poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), poly(HEMA-GMA), cryogels were synthesized. Heavy metal adsorption was carried out in wastewater obtained from six different sources in Çorum, Turkey. This study has a novelty regarding the application, i.e., it is the first time to use a polymeric adsorbent for the removal of 15 different heavy metal at the same time without any competition (despite the fact that there is a competition between the metals, the only thing is the removal regarding the purpose the study) as a heavy metal sweeper. Inductively coupled plasma-mass spectrometer (ICP-MS) was used for the determination of the initial amount of heavy metal in the wastewater samples. Adsorption studies were performed using poly(HEMA-GMA) and NAA-decorated poly(HEMA-GMA) cryogel to see the effect of NAA decoration. Higher adsorption capacity was achieved using NAA decorated poly(HEMA-GMA) cryogel. The total heavy metal amount adsorbed from six different sources was about 686 and 387 mg for poly(HEMA-GMA)-NAA and poly(HEMA-GMA) cryogels, respectively. The highest heavy metal adsorption value was obtained in the wastewater from source 2, and Zn (II) was the heavy metal adsorbed most for both cryogel. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal, surface area, elemental, and computerized microtomography (μCT) analyses were used for the characterization of cryogels.

Preparation and properties of cryogel based on poly(hydroxypropyl methacrylate)

A novel supermacroporous poly(hydroxypropyl methacrylate) (p(HPMA)) cryogel was synthesized by cryogelation method at -16 °C. In this synthesis process, HPMA was used as a monomer, and N,N'-methylenebisacrylamide (MBAAm) was used as cross-linker; the reaction was carried out in the presence of redox initiator pair N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS). The effect of monomer concentration, cross-linker content, cooling rate, and dioxane co-solvent were determined with respect to the pore structure, mechanical behavior, swelling degree, and porosity of cryogel. The ESEM images indicate that the pore wall structure of cryogels was rough; moreover, small holes were present in the pore walls of cryogels. The result of compression test indicates that cryogels can be compressed by at least 80% without any breakdown. The result of swelling kinetics indicates that cryogels attain swelling equilibrium in 10 s. Furthermore, p(HPMA)-Cu²⁺ cryogel was prepared by loading Cu²⁺ ions on functionalized poly(hydroxypropyl methacrylate)-iminodiacetic acid (p(HPMA)-IDA) cryogel. We investigated the adsorption of bovine serum albumin (BSA) on cryogels. The results indicate that compared to Freundlich isotherm, Langmuir isotherm could more suitably describe the adsorption process of BSA on cryogels. Meanwhile, the adsorption capacity of p(HPMA)-Cu²⁺ cryogel was significantly greater than that of p(HPMA) cryogel. The maximum adsorption capacity of BSA on p(HPMA)-Cu²⁺ cryogel, which was treated with 1 M Cu²⁺ ions, was as high as 196.87 mg/g cryogel (equivalent to 20.48 mg/mL cryogel) at 25 °C and pH = 7.8; therefore, the maximum adsorption capacity of BSA on p(HPMA)-Cu²⁺ cryogel was 4.35 times higher than that of p(HPMA) cryogel. Thus, the adsorption capacity of cryogels was strongly influenced by Cu²⁺ concentration, moreover, temperature changes clearly affected the adsorption capacity of p(HPMA)-Cu²⁺cryogel. The adsorption capacity at 25 °C was twice as that at 15 °C. By calculating Gibbs free energy change (∆G) of adsorption, we found that the adsorption process was spontaneous; moreover, adsorption process occurred better at higher temperature.

Affinity monolith chromatography: A review of general principles and applications

Affinity monolith chromatography, or AMC, is a liquid chromatographic method in which the support is a monolith and the stationary phase is a biological-binding agent or related mimic. AMC has become popular for the isolation of biochemicals, for the measurement of various analytes, and for studying biological interactions. This review will examine the principles and applications of AMC. The materials that have been used to prepare AMC columns will be discussed, which have included various organic polymers, silica, agarose, and cryogels. Immobilization schemes that have been used in AMC will also be considered. Various binding agents and applications that have been reported for AMC will then be described. These applications will include the use of AMC for bioaffinity chromatography, immunoaffinity chromatography, dye-ligand affinity chromatography, and immobilized metal-ion affinity chromatography. The use of AMC with chiral stationary phases and as a tool to characterize biological interactions will also be examined.

A comprehensive review of cryogels and their roles in tissue engineering applications

The extracellular matrix is fundamental in providing an appropriate environment for cell interaction and signaling to occur. Replicating such a matrix is advantageous in the support of tissue ingrowth and regeneration through the field of tissue engineering. While scaffolds can be fabricated in many ways, cryogels have recently become a popular approach due to their macroporous structure and durability. Produced through the crosslinking of gel precursors followed by a subsequent controlled freeze/thaw cycle, the resulting cryogel provides a unique, sponge-like structure. Therefore, cryogels have proven advantageous for many tissue engineering applications including roles in bioreactor systems, cell separation, and scaffolding. Specifically, the matrix has been demonstrated to encourage the production of various molecules, such as antibodies, and has also been used for cryopreservation. Cryogels can pose as a bioreactor for the expansion of cell lines, as well as a vehicle for cell separation. Lastly, this matrix has shown excellent potential as a tissue engineered scaffold, encouraging regrowth at numerous damaged tissue sites in vivo. This review will briefly discuss the fabrication of cryogels, with an emphasis placed on their application in various facets of tissue engineering to provide an overview of this unique scaffold's past and future roles.

STATEMENT OF SIGNIFICANCE

Cryogels are unique scaffolds produced through the controlled freezing and thawing of a polymer solution. There is an ever-growing body of literature that demonstrates their applicability in the realm of tissue engineering as extracellular matrix analogue scaffolds; with extensive information having been provided regarding the fabrication, porosity, and mechanical integrity of the scaffolds. Additionally, cryogels have been reviewed with respect to their role in bioseparation and as cellular incubators. This all-inclusive view of the roles that cryogels can play is critical to advancing the technology and expanding its niche within biomaterials and tissue engineering research. To the best of the authors' knowledge, this is the first comprehensive review of cryogel applications in tissue engineering that includes specific looks at their growing roles as extracellular matrix analogues, incubators, and in bioseparation processes.

Catalase purification from rat liver with iron-chelated poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) cryogel discs

In this study, iron-chelated poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) (PHEMAGA/Fe(3+)) cryogel discs were prepared. The PHEMAGA/Fe(3+) cryogel discs were characterized by elemental analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, swelling tests, and surface area measurements. The PHEMAGA/Fe(3+) cryogel discs had large pores ranging from 10 to 100 µm with a swelling degree of 9.36 g H2O/g cryogel. Effects of pH, temperature, initial catalase concentration, and flow rate on adsorption capacity of the PHEMAGA/Fe(3+) cryogel discs were investigated. Maximum catalase adsorption capacity (62.6 mg/g) was obtained at pH 7.0, 25°C, and 3 mg/ml initial catalase concentration. The PHEMAGA/Fe(3+) cryogel discs were also tested for the purification of catalase from rat liver. After tissue homogenization, purification of catalase was performed using the PHEMAGA/Fe(3+) cryogel discs and catalase was obtained with a yield of 54.34 and 16.67 purification fold.

pH-gradient ion-exchange microbial cell chromatography as a simple method for microbial separation

Selective separation of specific microbial types from a heterogeneous microbial population, such as an environmental microbial community, is an important process for microbial research and biotechnological industries. In the present study, pH-gradient ion-exchange microbial cell chromatography (PIE-MCC) was developed as a new method for microbial separation. The proposed method enables target microorganisms to be separated from a microbial community based on differences in microbial surface characteristics, because these characteristics, such as the ζ (zeta)-potential, vary among microbial cells. PIE-MCC was conducted by controlling the adhesion and detachment of microbial cells to and from the carrier surface by manipulating the pH of the running buffer. As a proof of concept, microbial cell separation via PIE-MCC was demonstrated using pure-cultured strains, model mixtures of two different pure-cultured strains, and an environmental sample targeting uncultivated microorganisms; i.e., each pure-cultured strain showed unique chromatograms; specific single species were separated from the model mixture; and a specific, uncultivated target was separated from the environmental sample. The ζ-potential of several tested strains suggested that not only electrostatic interactions, but also other factors affected microbial adhesion to the carrier surface. The newly developed method has several potential advantages compared with other techniques, not only in terms of its microbial separation capability, but also in terms of its simplicity and ability to be scaled up. Thus, the method has the potential to be widely used for a variety of purposes in the microbiology and biotechnology fields.

Cell separation: Potentials and pitfalls

Cell separation techniques play an indispensable part in numerous basic biological studies and even clinical settings. Although various cell isolation methods with diverse applications have been devised so far, not all of them have been able to gain widespread popularity among researchers and clinicians. There is not a single method known to be advantageous over all cell isolation techniques, and in fact, it is the researcher's aim in performing a study that determines the most suitable method. A perfect method for one study might not be necessarily a proper choice for another and likewise, expensive and complex isolation methods might not always be the best choices. There are several criteria such as cell purity, viability, activation status, and frequency that need to be given serious thought before selecting an isolation technique. Moreover, time and cost are two of the key elements that should be taken into consideration before implementing a project. Hence, here we provide a succinct description of six more popular cell separation methods with respect to their principles, advantages, and disadvantages as well as their most common applications. We further provide several key features of each technique so that it helps the researchers to take the first step toward opting for the best method that fits well into their projects.

Glycopolymer-Functionalized Cryogels as Catch and Release Devices for the Pre-Enrichment of Pathogens

A highly porous cryogel is prepared and subsequently functionalized with an atom transfer radical polymerization (ATRP) initiator at the surface. Two new glycomonomers are introduced, which possess deprotected mannose as well as glucose moieties. These are copolymerized with N-isopropylacrylamide (NiPAm) from the cryogel surface, providing a highly hydrophilic porous material, which is characterized by SEM, FT-IR spectroscopy, and NMR spectroscopy. This functionalized support can be applied for affinity chromatography of whole cells owing to the high pore space and diameter. Such an application is exemplified by investigating the ability to capture Escherichia coli bacteria, revealing selective binding interactions of the bacteria with the mannose glycopolymer-functionalized cryogel surface. Thus, the presented glycopolymer-cryogel represents a promising material for affinity chromatography or enrichment of cells.

Development and characteristics of polymer monoliths for advanced LC bioscreening applications: A review

Biomedical research advances over the past two decades in bioseparation science and engineering have led to the development of new adsorbent systems called monoliths, mostly as stationary supports for liquid chromatography (LC) applications. They are acknowledged to offer better mass transfer hydrodynamics than their particulate counterparts. Also, their architectural and morphological traits can be tailored in situ to meet the hydrodynamic size of molecules which include proteins, pDNA, cells and viral targets. This has enabled their development for a plethora of enhanced bioscreening applications including biosensing, biomolecular purification, concentration and separation, achieved through the introduction of specific functional moieties or ligands (such as triethylamine, N,N-dimethyl-N-dodecylamine, antibodies, enzymes and aptamers) into the molecular architecture of monoliths. Notwithstanding, the application of monoliths presents major material and bioprocess challenges. The relationship between in-process polymerisation characteristics and the physicochemical properties of monolith is critical to optimise chromatographic performance. There is also a need to develop theoretical models for non-invasive analyses and predictions. This review article therefore discusses in-process analytical conditions, functionalisation chemistries and ligands relevant to establish the characteristics of monoliths in order to facilitate a wide range of enhanced bioscreening applications. It gives emphasis to the development of functional polymethacrylate monoliths for microfluidic and preparative scale bio-applications.

Cryogels with affinity ligands as tools in protein purification

Affinity chromatography is one of the well-known separation techniques especially if high purity is desired. Introducing ligands on monolithic structure gives the possibility for purifying complex media such as plasma and crude extract. This chapter is focusing on the preparation of cryogels as monolithic column and immobilization of concanavalin A on its surface as ligand for capturing the glycoprotein horseradish peroxidase.

Cryostructuring of polymer systems. Proteinaceous wide-pore cryogels generated by the action of denaturant/reductant mixtures on bovine serum albumin in moderately frozen aqueous media

Freeze-thaw processing of bovine serum albumin (BSA) aqueous solutions, which contain also the additives of denaturants (urea in this case) and thiol-bearing reductants [cysteine (Cys) in this case] leads to the formation of wide-pore cryogels. The properties and porous morphology of these spongy gel matrices were demonstrated to depend on the initial concentration of all precursors and on the freezing/frozen storage temperature. The optimum conditions for preparing such BSA-based cryogels were found to be as follows: [BSA] = 3-5 g dL(-1), [urea] = 0.5-2.0 mol L(-1), [Cys] = 0.01 mol L(-1), and freezing temperatures in the range of -15 to -20 °C. The size of gross pores in thus prepared cryogels is ∼50-150 μm. The spatial network of BSA-cryogels was shown to be cross-linked chemically via interchain disulfide bridges. The significant role of hydrophobic interactions in the stabilization of 3D networks of these cryogels is inferred, as well as the supposition about the relay-race sequence mechanism of the intermolecular disulfide cross-link formation is made.

Highly selective monitoring of metals by using ion-imprinted polymers

Ion imprinting technology is one of the most promising tools in separation and purification sciences because of its high selectivity, good stability, simplicity and low cost. It has been mainly used for selective removal, preconcentration, sensing and few miscellaneous fields. In this review article, recent methodologies in the synthesis of IIPs have been discussed. For several applications, different parameters of IIP including complexing and leaching agent, pH, relative selectivity coefficient, detection limit and adsorption capacity have been evaluated and an attempt has been made to generalize. Biomedical applications mostly include selective removal of toxic metals from human blood plasma and urine samples. Wastewater treatment involves selective removal of highly toxic metal ions like Hg(II), Pb(II), Cd(II), As(V), etc. Preconcentration covers recovery of economically important metal ions such as gold, silver, platinum and palladium. It also includes selective preconcentration of lanthanides and actinides. In sensing, various IIP-based sensors have been fabricated for detection of toxic metal ions. This review article includes almost all metal ions based on the ion-imprinted polymer. At the end, the future outlook section presents the discussion on the advancement, corresponding merits and the need of continued research in few specific areas. Graphical Abstract IIPs for the selective monitoring of metals.

Immobilization of alcohol dehydrogenase onto metal-chelated cryogels

In this presented work, poly(HEMA-GMA) cryogel was synthesized and used for the immobilization of alcohol dehydrogenase. For this, synthesized cryogels were functionalized with iminodiacetic acid and chelated with Zn(2+). This metal-chelated cryogels were used for the alcohol dehydrogenase immobilization and their kinetic parameters were compared with free enzyme. Optimum pH was found to be 7.0 for both immobilized and free enzyme preparations, while temperature optima for free and immobilized alcohol dehydrogenase was 25 °C. Kinetic constants such as K(m), V(max), and k(cat) for free and immobilized form of alcohol dehydrogenase were also investigated. k(cat) value of free enzyme was found to be 3743.9 min(-1), while k(cat) for immobilized enzyme was 3165.7 min(-1). Thermal stability of the free and immobilized alcohol dehydrogenase was studied and stability of the immobilized enzyme was found to be higher than free form. Also, operational stability and reusability profile of the immobilized alcohol dehydrogenase were investigated. Finally, storage stability of the free and immobilized alcohol dehydrogenase was studied, and at the end of the 60 days storage, it was demonstrated that, immobilized alcohol dehydrogenase was exhibited high stability than that of free enzyme.

Direct capture of His₆-tagged proteins using megaporous cryogels developed for metal-ion affinity chromatography

Immobilized metal-ion affinity chromatography (IMAC) has been developed for the rapid isolation and purification of recombinant proteins. In this chapter, megaporous cryogels were synthesized having metal-ion affinity functionality, and their adsorptive properties were investigated. These cryogels have large pore sizes ranging from 10 to 100 μm with corresponding porosities between 80 and 90%. The synthesized IMAC-cryogel had a total ligand density of 770 μmol/g. Twelve milligram of a His6-tagged protein (NAD(P)H-dependent 2-cyclohexen-1-one-reductase) can be purified from a crude cell extract per gram of IMAC-cryogels. The protein binding capacity is increased with higher degrees of grafting, although a slight decrease in column efficiency may result. This chapter provides methodologies for a rapid single-step purification of recombinant His6-tagged proteins from crude cell extracts using IMAC-cryogels.

Grafting zwitterionic polymer onto cryogel surface enhances protein retention in steric exclusion chromatography on cryogel monolith

Cryogel monoliths with interconnected macropores (10-100μm) and hydrophilic surfaces can be employed as chromatography media for protein retention in steric exclusion chromatography (SXC). SXC is based on the principle that the exclusion of polyethylene glycol (PEG) on both a hydrophilic chromatography surface and a protein favors their association, leading to the protein retention on the chromatography surface. Elution of the retained protein can be achieved by reducing PEG concentration. In this work, the surface of polyacrylamide-based cryogel monolith was modified by grafting zwitterionic poly(carboxybetaine methacrylate) (pCBMA), leading the increase in the surface hydrophilicity. Observation by scanning electron microscopy revealed the presence of the grafted pCBMA chain clusters on the cryogel surface, but pCBMA grafting did not result in the changes of the physical properties of the monolith column, and the columns maintained good recyclability in SXC. The effect of the surface grafting on the SXC behavior of γ-globulin was investigated in a wide flow rate range (0.6-12cm/min). It was found that the dynamic retention capacity increased 1.4-1.8 times by the zwitterionic polymer grafting in the flow rate range of 1.5-12cm/min. The mechanism of enhanced protein retention on the zwitterionic polymer-grafted surface was proposed. The research proved that zwitterionic polymer modification was promising for the development of new materials for SXC applications.