3D-printed ordered bed structures for chromatographic purification of enveloped and non-enveloped viral particles

Optimizing Low-Cost Gas Analysis with a 3D Printed Column and MiCS-6814 Sensor for Volatile Compound Detection

This paper explores an application of 3D printing technology on the food industry. Since its inception in the 1980s, 3D printing has experienced a huge rise in popularity. This study uses cost-effective, flexible, and sustainable components that enable specific features of certain gas chromatography. This study aims to optimize the process of gas detection using a 3D printed separation column and the MiCS-6814 sensor. The principle of the entire device is based on the idea of utilizing a simple capillary chromatographic column manufactured by 3D printing for the separation of samples into components prior to their measurement using inexpensive chemiresistive sensors. An optimization of a system with a 3D printed PLA block containing a capillary, a mixing chamber, and a measuring chamber with a MiCS-6814 sensor was performed. The optimization distributed the sensor output signal in the time domain so that it was possible to distinguish the peak for the two most common alcohols, ethanol and methanol. The paper further describes some optimization types and their possibilities.

Purification of his-tagged proteins using printed monolith adsorption columns

Bio-separation is a crucial process in biotechnology and biochemical engineering for separating biological macromolecules, and the field has long relied on bead-based and expanded bed chromatography. Printed monolith adsorption (PMA) is a new alternative to which uses a 3D-printed monolithic structure containing self-supporting, ordered flow channels. PMA allows for direct purification of biological molecules from crude cell lysates and cell cultures, and like the other technologies, can functionalized to specifically target a molecule and enable affinity chromatography. Here we have combined PMA technology with an immobilized metal affinity ligand (iminodiacetic acid) to provide selectivity of binding to polyhistidine-tagged proteins during PMA chromatography. Two different PMA structures were created and tested for both static and dynamic protein-binding capacity. At comparative linear flow rates, the dynamic binding capacity of both columns was ≈3 mg/mL, while static capacity was shown to differentiate based on column voidage. We show that a polyhistidine-tagged protein can be directly purified from crude lysate with comparable results to the available commercial providers of IMAC, and with a substantially reduced purification time.

Performance of various 3D-printed monolith geometries as an alternative to expanded bed adsorption for protein purification

Here, we compare the performance of various three-dimensional-printed Monolith Adsorption (PMA) columns designed from a triply periodic minimal surface geometry, the Schoen gyroid. The structures examined had designed hydraulic diameters between 203 and 458 µm and voidages of 40%-60%. We compare column efficiency, porosity, static binding capacity and dynamic binding capacity for various load volumes and flow rates. The results show that all structures allowed efficient passage of yeast cells (>97%) over a wide range of interstitial velocities (191 to 1911 cm/h) while maintaining a low pressure drop (<0.1 MPa). The structure with a voidage of 40% and a hydraulic diameter of 203 µm showed the best performance in all aspects evaluated. Bovine serum albumin (BSA) recoveries for all structures (27%-91% when the loaded volume was 180 mL) were significantly affected by hydraulic diameter, mean channel wall thickness, velocity and voidage. Moreover, biomass addition resulted in a decrease in BSA recovery, which became more obvious at high velocities. However, this did not lead to a dramatic reduction in saturated binding capacity, significant changes in axial dispersion, or blockage of channels and could be compensated for by recirculation of the feed, even at high velocity. PMA thus potentially provides an appealing alternative to Expanded Bed Adsorption, retaining the latter's advantages, while eliminating fluidization issues and minimizing both processing time and buffer consumption.

Influence of porosity and microstructure on compression behavior of methacrylate polymers in flow-through applications

Mechanical properties of a material play a pivotal role in its performance when such porous material is used in a flow-through mode. This study delves into the effect of porosity and microstructure on the compressibility of methacrylate polymer, focusing on two distinct microstructures: cauliflower and high internal phase emulsion. Samples with various porosities yet identical chemical composition were prepared and their Young's modulus was measured. The effect of porosity on Young's modulus was described by an exponential law model with the cauliflower microstructure exhibiting an exponent of 3.61, while the high internal phase emulsion of only 1.86. A mathematical analysis of the compression caused by a liquid flow unveiled significant disparities in the porosity threshold where minimal compression is observed, being around 0.45 for the cauliflower while there is monotone decrease in compression with porosity increase for the high internal phase emulsion microstructure. Evaluating exponent integer values between 1 and 5 over entire porosity range reveals that the porosity where the minimal compression occurs increases with a decrease in exponent value, being approximately 0.33 for n = 5, 0.4 for n = 4, 0.55 for n = 3, 0.65 for n = 2 while no minimum occurs for n = 1. These findings indicate that lower exponent value results in lower compression under identical experimental conditions.

Purification of monoclonal antibodies using novel 3D printed ordered stationary phases

3D printing offers the unprecedented ability to fabricate chromatography stationary phases with bespoke 3D morphology as opposed to traditional packed beds of spherical beads. The restricted range of printable materials compatible with chromatography is considered a setback for its industrial implementation. Recently, we proposed a novel ink that exhibits favourable printing performance (printing time ∼100 mL/h, resolution ∼200 µm) and broadens the possibilities for a range of chromatography applications thanks to its customisable surface chemistry. In this work, this ink was used to fabricate 3D printed ordered columns with 300 µm channels for the capture and polishing of therapeutic monoclonal antibodies. The columns were initially assessed for leachables and extractables, revealing no material propensity for leaching. Columns were then functionalised with protein A and SO3 ligands to obtain affinity and strong cation exchangers, respectively. 3D printed protein A columns showed >85 % IgG recovery from harvested cell culture fluid with purities above 98 %. Column reusability was evaluated over 20 cycles showing unaffected performance. Eluate samples were analysed for co-eluted protein A fragments, host cell protein and aggregates. Results demonstrate excellent HCP clearance (logarithmic reduction value of > 2.5) and protein A leakage in the range of commercial affinity resins (<100 ng/mg). SO3 functionalised columns employed for polishing achieved removal of leaked Protein A (down to 10 ng/mg) to meet regulatory expectations of product purity. This work is the first implementation of 3D printed columns for mAb purification and provides strong evidence for their potential in industrial bioseparations.

Peptide ligands targeting the vesicular stomatitis virus G (VSV-G) protein for the affinity purification of lentivirus particles

The recent uptick in the approval of ex vivo cell therapies highlights the relevance of lentivirus (LV) as an enabling viral vector of modern medicine. As labile biologics, however, LVs pose critical challenges to industrial biomanufacturing. In particular, LV purification-currently reliant on filtration and anion-exchange or size-exclusion chromatography-suffers from long process times and low yield of transducing particles, which translate into high waiting time and cost to patients. Seeking to improve LV downstream processing, this study introduces peptides targeting the enveloped protein Vesicular stomatitis virus G (VSV-G) to serve as affinity ligands for the chromatographic purification of LV particles. An ensemble of candidate ligands was initially discovered by implementing a dual-fluorescence screening technology and a targeted in silico approach designed to identify sequences with high selectivity and tunable affinity. The selected peptides were conjugated on Poros resin and their LV binding-and-release performance was optimized by adjusting the flow rate, composition, and pH of the chromatographic buffers. Ligands GKEAAFAA and SRAFVGDADRD were selected for their high product yield (50%-60% of viral genomes; 40%-50% of HT1080 cell-transducing particles) upon elution in PIPES buffer with 0.65 M NaCl at pH 7.4. The peptide-based adsorbents also presented remarkable values of binding capacity (up to 3·109 TU per mL of resin, or 5·1011 vp per mL of resin, at the residence time of 1 min) and clearance of host cell proteins (up to a 220-fold reduction of HEK293 HCPs). Additionally, GKEAAFAA demonstrated high resistance to caustic cleaning-in-place (0.5 M NaOH, 30 min) with no observable loss in product yield and quality.

The downstream bioprocess toolbox for therapeutic viral vectors

Viral vectors are poised to acquire a prominent position in modern medicine and biotechnology owing to their role as delivery agents for gene therapies, oncolytic agents, vaccine platforms, and a gateway to engineer cell therapies as well as plants and animals for sustainable agriculture. The success of viral vectors will critically depend on the availability of flexible and affordable biomanufacturing strategies that can meet the growing demand by clinics and biotech companies worldwide. In this context, a key role will be played by downstream process technology: while initially adapted from protein purification media, the purification toolbox for viral vectors is currently undergoing a rapid expansion to fit the unique biomolecular characteristics of these products. Innovation efforts are articulated on two fronts, namely (i) the discovery of affinity ligands that target adeno-associated virus, lentivirus, adenovirus, etc.; (ii) the development of adsorbents with innovative morphologies, such as membranes and 3D printed monoliths, that fit the size of viral vectors. Complementing these efforts are the design of novel process layouts that capitalize on novel ligands and adsorbents to ensure high yield and purity of the product while safeguarding its therapeutic efficacy and safety; and a growing panel of analytical methods that monitor the complex array of critical quality attributes of viral vectors and correlate them to the purification strategies. To help explore this complex and evolving environment, this study presents a comprehensive overview of the downstream bioprocess toolbox for viral vectors established in the last decade, and discusses present efforts and future directions contributing to the success of this promising class of biological medicines.

Evaluating 3D-printed bioseparation structures using multi-length scale tomography

X-ray computed tomography was applied in imaging 3D-printed gyroids used for bioseparation in order to visualize and characterize structures from the entire geometry down to individual nanopores. Methacrylate prints were fabricated with feature sizes of 500 µm, 300 µm, and 200 µm, with the material phase exhibiting a porous substructure in all cases. Two X-ray scanners achieved pixel sizes from 5 µm to 16 nm to produce digital representations of samples across multiple length scales as the basis for geometric analysis and flow simulation. At the gyroid scale, imaged samples were visually compared to the original computed-aided designs to analyze printing fidelity across all feature sizes. An individual 500 µm feature, part of the overall gyroid structure, was compared and overlaid between design and imaged volumes, identifying individual printed layers. Internal subvolumes of all feature sizes were segmented into material and void phases for permeable flow analysis. Small pieces of 3D-printed material were optimized for nanotomographic imaging at a pixel size of 63 nm, with all three gyroid samples exhibiting similar geometric characteristics when measured. An average porosity of 45% was obtained that was within the expected design range, and a tortuosity factor of 2.52 was measured. Applying a voidage network map enabled the size, location, and connectivity of pores to be identified, obtaining an average pore size of 793 nm. Using Avizo XLAB at a bulk diffusivity of 7.00 × 10-11 m2s-1 resulted in a simulated material diffusivity of 2.17 × 10-11 m2s-1 ± 0.16 × 10-11 m2s-1.

Assessing Multi-Attribute Characterization of Enveloped and Non-Enveloped Viral Particles by Capillary Electrophoresis

Virus-based biopharmaceutical products are used in clinical applications such as vaccines, gene therapy, and immunotherapy. However, their manufacturing remains a challenge, hampered by the lack of appropriate analytical tools for purification monitoring or characterization of the final product. This paper describes the implementation of a highly sensitive method, capillary electrophoresis (CE)-sodium dodecyl sulfate (SDS) combined with a laser-induced fluorescence (LIF) detector to monitor the impact of various bioprocess steps on the quality of different viral vectors. The fluorescence labelling procedure uses the (3-(2-furoyl) quinoline-2-carboxaldehyde dye, and the CE-SDS LIF method enables the evaluation of in-process besides final product samples. This method outperforms other analytical methods, such as SDS-polyacrylamide gel electrophoresis with Sypro Ruby staining, in terms of sensitivity, resolution, and high-throughput capability. Notably, this CE-SDS LIF method was also successfully implemented to characterize enveloped viruses such as Maraba virus and lentivirus, whose development as biopharmaceuticals is now restricted by the lack of suitable analytical tools. This method was also qualified for quantification of rAAV2 according to the International Council for Harmonisation guidelines. Overall, our work shows that CE-SDS LIF is a precise and sensitive analytical platform for in-process sample analysis and quantification of different virus-based targets, with a great potential for application in biomanufacturing.

Human Mastadenovirus Infections in Children: A Review of the Current Status in the Arab World in the Middle East and North Africa

Human mastadenovirus (HAdV) is a non-enveloped icosahedral virus with double-stranded DNA genomes. The mortality rate of HAdV infections can reach 35.5%, while gastroenteritis HAdV infections, HAdV pneumonia, and disseminated disease tend to show a worse outcome, with rates ranging from 44.2% to 50%. In addition, HAdV can cause infections at any age but most commonly in the pediatric population, especially in young children and infants. Therefore, this review aims to assess the current status of HAdV infections among children in the Arab World, particularly in the Middle East and North Africa. Web of Science, Scopus, PubMed, EMBASE, and Google Scholar databases for publications in English were searched up to July 2022 for relevant articles. The literature search yielded a total of 21 studies, which were included in this review. Studies reporting HAdV infections in children were conducted in 17 out of the 22 countries. The average prevalence rate of HAdV infections in children was 12.7%, with average prevalence rates of 12.82% and 12.58% in the Middle East and North African countries, respectively. The highest prevalence rate (28.3%) was reported in Egypt, whereas the lowest prevalence (1.5%) was reported in Sudan. The included studies presented children with signs and symptoms of gastroenteritis, acute respiratory infection, acute diarrhea, and acute hemorrhagic conjunctivitis. In conclusion, the average prevalence rate of HAdV infections in children was 12.7%, with average prevalence rates of 12.82% and 12.58% in the Middle East and North African countries, respectively. Finding the precise prevalence rate of this virus is crucial because it will guide future planning for effective disease control and the selection of particular treatment options during epidemics and special seasons.

On the potential use of two-photon polymerization to 3D print chromatographic packed bed supports

The continuous quest for chromatographic supports offering kinetic performance properties superior to that of the packed bed of spheres has pushed the field to consider alternative formats such as for example monolithic and pillar array columns. This quest seems bound to culminate in the use of 3D printing technology, as this intrinsically offers the possibility to produce supports with a perfect uniformity and with a size and shape that is fully optimized for the chromatographic separation process. However, to be competitive with the current state-of-the-art, structures with sub-micron feature sizes are required. The present contribution therefore investigates the use of the 3D printing technology with the highest possible resolution available today, i.e., two-photon polymerization (2PP). It is shown that 2PP printing is capable of achieving the required ≤ 1 µm printing resolution. Depending on the laser scan speed, the lower limit through-pore size for a tetrahedral skeleton monolith with a theoretical 80% external porosity was found to be at 800 nm, when printing at a scan speed of 50 mm/s with a laser power of 10%. For a scan speed of 10 mm/s, the minimal through-pore size dropped to 500 nm. However, this very high resolution comes at the cost of excessively long printing times. The total printing time for a column volume equivalent to that of a typical nano-LC column (75 µm i.d. cylindrical tube with length L = 15 cm) has been determined to correspond to 330 and 470 h for the 50 mm/s and the 10 mm/s scan speed respectively. Other issues remaining to be solved are the need to clad the printed skeleton with a suitable mesoporous layer for chromatographic retention and the need to add a top-wall to the printed channels after the removal of the non-polymerized resin. It is therefore concluded that 2PP printing is not ready yet to replace the existing column fabrication methods.

Development of a 3D-printed single-use separation chamber for use in mRNA-based vaccine production with magnetic microparticles

Laboratory protocols using magnetic beads have gained importance in the purification of mRNA for vaccines. Here, the produced mRNA hybridizes specifically to oligo(dT)-functionalized magnetic beads after cell lysis. The mRNA-loaded magnetic beads can be selectively separated using a magnet. Subsequently, impurities are removed by washing steps and the mRNA is eluted. Magnetic separation is utilized in each step, using different buffers such as the lysis/binding buffer. To reduce the time required for purification of larger amounts of mRNA vaccine for clinical trials, high-gradient magnetic separation (HGMS) is suitable. Thereby, magnetic beads are selectively retained in a flow-through separation chamber. To meet the requirements of biopharmaceutical production, a disposable HGMS separation chamber with a certified material (United States Pharmacopeia Class VI) was developed which can be manufactured using 3D printing. Due to the special design, the filter matrix itself is not in contact with the product. The separation chamber was tested with suspensions of oligo(dT)-functionalized Dynabeads MyOne loaded with synthetic mRNA. At a concentration of cB = 1.6-2.1 g·L-1 in lysis/binding buffer, these 1 μm magnetic particles are retained to more than 99.39% at volumetric flows of up to 150 mL·min-1 with the developed SU-HGMS separation chamber. When using the separation chamber with volumetric flow rates below 50 mL·min-1, the retained particle mass is even more than 99.99%.

How 3D printing can boost advances in analytical and bioanalytical chemistry

3D printing fabrication methods have received lately an enormous attention by the scientific community. Laboratories and research groups working on analytical chemistry applications, among others, have advantageously adopted 3D printing to fabricate a wide range of tools, from common laboratory hardware to fluidic systems, sample treatment platforms, sensing structures, and complete fully functional analytical devices. This technology is becoming more affordable over time and therefore preferred over the commonly used fabrication processes like hot embossing, soft lithography, injection molding and micromilling. However, to better exploit 3D printing fabrication methods, it is important to fully understand their benefits and limitations which are also directly associated to the properties of the materials used for printing. Costs, printing resolution, chemical and biological compatibility of the materials, design complexity, robustness of the printed object, and integration with commercially available systems represent important aspects to be weighted in relation to the intended task. In this review, a useful introductory summary of the most commonly used 3D printing systems and mechanisms is provided before the description of the most recent trends of the use of 3D printing for analytical and bioanalytical chemistry. Concluding remarks will be also given together with a brief discussion of possible future directions.

Theoretical study of the efficiency of liquid chromatography columns with particle size gradient

Modern analytical applications of liquid chromatography require more and more efficient columns. In this work, the possibility of utilizing particle size gradient in the chromatographic column was studied by a theoretical approach. In the course of our work three different scenarios of particle size gradients were considered with different shapes (linear, convex and concave). The evolution of bandwidth inside the column was plotted for each scenario. As a reference point, the bandwidth of the uniform column was used, which had the same pressure drop as the non-uniform column. According to our calculations, in isocratic elution mode, the non-uniform column does not offer any advantage compared to the uniform column, regardless the type of the particle size gradient. In gradient elution mode, however, extra band compression occurs was found. For negative particle size gradients, the final physical bandwidth was found to be approximately 1-4 % smaller than for uniform columns. This slight gain in efficiency in terms of bandwidth compression can be expanded to 5-8 % by the optimization of the limiting particle sizes. These optimized results are obtained when the final particle size is approximately 40% of the initial particle diameter.

Downstream processing for influenza vaccines and candidates: An update

Seasonal and pandemic influenza outbreaks present severe health and economic burdens. To overcome limitations on influenza vaccines' availability and effectiveness, researchers chase universal vaccines providing broad, long-lasting protection against multiple influenza subtypes, and including pandemic ones. Novel influenza vaccine designs are under development, in clinical trials, or reaching the market, namely inactivated, or live-attenuated virus, virus-like particles, or recombinant antigens, searching for improved effectiveness; all these bring downstream processing (DSP) new challenges. Having to deal with new influenza strains, including pandemics, requires shorter development time, driving the development of faster bioprocesses. To cope with better upstream processes, new regulatory demands for quality and safety, and cost reduction requirements, new unit operations and integrated processes are increasing DSP efficiency for novel vaccine formats. This review covers recent advances in DSP strategies of different influenza vaccine formats. Focus is given to the improvements on relevant state-of-the-art unit operations, from harvest and clarification to purification steps, ending with sterile filtration and formulation. The development of more efficient unit operations to cope with biophysical properties of the new candidates is discussed: emphasis is given to the design of new stationary phases, 3D printing approaches, and continuous processing tools, such as continuous chromatography. The impact of the production platforms and vaccine designs on the downstream operations for the different influenza vaccine formats approved for this season are highlighted.

Additive Manufacturing Tools to Improve the Performance of Chromatographic Approaches

Chromatography is widely applied industrially. However, some limitations are associated with its common supports, and the impossibility to fully control their structural features is particularly restrictive. Additive manufacturing (AM) is emerging as a fast, highly precise, and reproducible technology for producing chromatographic supports that can improve its performance.

Experimental investigation and mass transfer modelling of 3D printed monolithic cation exchangers

3D printing has recently found application in chromatography as a means to create ordered stationary phases with improved separation efficiency. Currently, 3D printed stationary phases are limited by the lack of 3D printing materials suitable for chromatographic applications, and require a strict compromise in terms of desired resolution, model size and the associated print time. Modelling of mass transfer in 3D printed monoliths is also fundamental to understand and further optimise separation performance of 3D printed stationary phases. In this work, a novel 3D printing material was formulated and employed to fabricate monolithic cation exchangers (CEXs) with carboxyl functionalities. CEXs were printed with ligand densities of 0.7, 1.4, 2.1 and 2.8 mmol/g and used in batch adsorption experiments with lysozyme as model protein. All CEXs demonstrated high binding strength towards lysozyme, with maximum binding capacities of up to 108 mg/mL. The experimental results were described using mass transfer models based on lumped pore diffusion and lumped solid diffusion mechanisms adapted to reflect the complex geometry of the 3D printed monoliths. An exact 3D model as well as less computationally demanding 1D and 2D approximations were evaluated in terms of their quality to capture the experimental trend of batch adsorption kinetic data. Overall, the model results indicate that mass transfer in the fabricated CEXs is mostly controlled by pore diffusion at high protein concentrations in the mobile phase, with solid diffusion becoming important at low protein concentrations. Also, the kinetic data were approximated equally well by both the full 3D model as well as the 2D approximation, indicating leaner mathematical models of lower dimensionality can be employed to describe mass transfer in complex three dimensional geometries. We believe this work will help spur the development of 3D printable materials for separations and aid in the development of quantitative platforms to evaluate and optimise the performance of 3D printed monoliths.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.