Large-volume methacrylate monolith for plasmid purification

Preparation and evaluation of 400μm I.D. polymer-based hydrophilic interaction chromatography monolithic columns with high column efficiency

The quest for higher column efficiency is one of the major research areas in polymer-based monolithic column fabrication. In this research, two novel polymer-based HILIC monolithic columns with 400μm I.D.×800μm O.D. were prepared based on the thermally initiated co-polymerization of N,N-dimethyl-N-(3-methacrylamidopropyl)-N-(3-sulfopropyl) ammonium betaine (SPP) and ethylene glycol dimethacrylate (EDMA) or N,N'-methylenebisacrylamide (MBA). In order to obtain a satisfactory performance in terms of column permeability, mechanical stability, efficiency and selectivity, the polymerization parameters were systematically optimized. Column efficiencies as high as 142, 000 plates/m and 120, 000 plates/m were observed for the analysis of neutral compounds at 0.6mm/s on the poly(SPP-co-MBA) and poly(SPP-co-EDMA) monoliths, respectively. Furthermore, the Van Deemter plots for thiourea on the two monoliths were compared with that on a commercial silica based ZIC-HILIC column (3.5μm, 200Å, 150mm×300μm I.D.) using ACN/H₂O (90/10, v/v) as the mobile phase at room temperature. It was noticeable that the Van Deemter curves for both monoliths, particularly the poly(SPP-co-MBA) monolith, are significantly flatter than that obtained for the ZIC-HILIC column, which indicates that in spite of their larger internal diameters, they yield better overall efficiency, with less peak dispersion, across a much wider range of usable linear velocities. A clearly better separation performance was also observed for nucleobases, nucleosides, nucleotides and small peptides on the poly(SPP-co-MBA) monolith compared to the ZIC-HILIC column. It is particularly worth mentioning that these 400μm I.D. polymer-based HILIC monolithic columns exhibit enhanced mechanical strength owing to the thicker capillary wall of the fused-silica capillaries.

DNA manipulation by means of insulator-based dielectrophoresis employing direct current electric fields

Electrokinetic techniques offer a great potential for biological particle manipulation. Among these, dielectrophoresis (DEP) has been successfully utilized for the concentration of bioparticles. Traditionally, DEP is performed employing microelectrodes, an approach with attractive characteristics but expensive due to microelectrode fabrication costs. An alternative is insulator-based DEP, a method where non-uniform electric fields are created with arrays of insulating structures. This study presents the concentration of linear DNA particles (pET28b) employing a microchannel, with an array of cylindrical insulating structures and direct current electric fields. Results showed manipulation of DNA particles with a combination of electroosmotic, electrophoretic, and dielectrophoretic forces. Employing suspending media with conductivity of 104 muS/cm and pH of 11.15, under applied fields between 500 and 1500 V/cm, DNA particles were observed to be immobilized due to negative dielectrophoretic trapping. The observation of DNA aggregates that occurred at higher applied fields, and dispersed once the field was removed is also included. Finally, concentration factors varying from 8 to 24 times the feed concentration were measured at 2000 V/cm after concentration time-periods of 20-40 s. The results presented here demonstrate the potential of insulator-based DEP for DNA concentration, and open the possibility for fast DNA manipulation for laboratory and large-scale applications.

Porous polymer monoliths: amazingly wide variety of techniques enabling their preparation

The porous polymer monoliths went a long way since their invention two decades ago. While the first studies applied the traditional polymerization processes at that time well established for the preparation of polymer particles, creativity of scientists interested in the monolithic structures has later led to the use of numerous less common techniques. This review article presents vast variety of methods that have meanwhile emerged. The text first briefly describes the early approaches used for the preparation of monoliths comprising standard free radical polymerizations and includes their development up to present days. Specific attention is paid to the effects of process variables on the formation of both porous structure and pore surface chemistry. Specific attention is also devoted to the use of photopolymerization. Then, several less common free radical polymerization techniques are presented in more detail such as those initiated by gamma-rays and electron beam, the preparation of monoliths from high internal phase emulsions, and cryogels. Living processes including stable free radicals, atom transfer radical polymerization, and ring-opening metathesis polymerization are also discussed. The review ends with description of preparation methods based on polycondensation and polyaddition reactions as well as on precipitation of preformed polymers affording the monolithic materials.

Versatility of polymethacrylate monoliths for chromatographic purification of biomolecules

Polymethacrylate monoliths, specifically poly(glycidyl methacrylate-co-ethylene dimethacrylate) or poly(GMA-co-EDMA) monoliths, are a new generation of chromatographic supports and are significantly different from conventional particle-based adsorbents, membranes, and other monolithic supports for biomolecule purification. Similar to other monoliths, polymethacrylate monoliths possess large pores which allow convective flow of mobile phase and result in high flow rates at reduced pressure drop, unlike particulate supports. The simplicity of the adsorbent synthesis, pH resistance, and the ease and flexibility of tailoring their pore size to that of the target biomolecule are the key properties which differentiate polymethacrylate monoliths from other monoliths. Polymethacrylate monoliths are endowed with reactive epoxy groups for easy functionalization (with anion-exchange, hydrophobic, and affinity ligands) and high ligand retention. In this review, the structure and performance of polymethacrylate monoliths for chromatographic purification of biomolecules are evaluated and compared to those of other supports. The development and use of polymethacrylate monoliths for research applications have grown rapidly in recent times and have enabled the achievement of high through-put biomolecule purification on semi-preparative and preparative scales.

DNA vaccine manufacture: scale and quality

The demand for plasmid DNA in large quantities at high purity and concentration is expected to escalate as more DNA vaccines are entering clinical trial status and becoming closer to market approval. This review outlines different methods for DNA vaccine manufacture and discusses the challenges that hinder large-scale production. Current technologies are summarized, focusing on novel approaches that have the potential to address downstream bottlenecks and adaptability for large-scale application. Product quality in terms of supercoiled percentage and impurity levels are compared at the different production levels.