A simplified implementation of the stationary liquid mass balance method for on-line OUR monitoring in animal cell cultures

This is the peer reviewed version of the following article: [Fontova, A. , Lecina, M. , López‐Repullo, J. , Martínez‐Monge, I. , Comas, P. , Bragós, R. and Cairó, J. J. (2018), A simplified implementation of the stationary liquid mass balance method for on‐line OUR monitoring in animal cell cultures. J. Chem. Technol. Biotechnol. doi:10.1002/jctb.5551], which has been published in final form at [doi:10.1002/jctb.5551]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.BACKGROUND: Compared with other methods, the stationary liquid mass balance method for oxygen uptake rate (OUR) determination offers advantages in terms of estimation accuracy and reduction of stress. However, the need for sophisticated instrumentation, like mass flow controllers and gas analysers, has historically limited wider implementation of such a method. In this paper, a new simplified method based on inexpensive valves for the continuous estimation of OUR in animal cell cultures is evaluated. The determination of OUR values is based on accurate operation of the dissolved oxygen (DO) control loop and monitoring of its internal variables. RESULTS: The method developed was tested empirically in 2¿L bioreactor HEK293 batch cultures. OUR profiles obtained by a dynamic method, global mass balance method and the developed simplified method were monitored and compared. The results show how OUR profile obtained with the proposed method better follows the off-line cell density determination. The OUR estimation frequency was also increased, improving the method capabilities and applications. The theoretical rationale of the method was extended to the sensitivity analysis which was analytically and numerically approached. CONCLUSIONS: The results showed the proposed method to be not only cheap, but also a reliable alternative to monitor the metabolic activity in bioreactors in many biotechnological processes, being a useful tool for high cell density culture strategies implementation based on OUR monitoring.Peer ReviewedPostprint (published version

PEI-mediated transient transfection of High Five cells at bioreactor scale for HIV-1 VLP production

High Five cells are an excellent host for the production of virus-like particles (VLPs) with the baculovirus expression vector system (BEVS). However, the concurrent production of high titers of baculovirus hinder the purification of these nanoparticles due to similarities in their physicochemical properties. In this study, first a transient gene expression (TGE) method based on the transfection reagent polyethylenimine (PEI) is optimized for the production of HIV-1 VLPs at shake flask level. Furthermore, VLP production by TGE in High Five cells is successfully demonstrated at bioreactor scale, resulting in a higher maximum viable cell concentration (5.1 × 106 cell/mL), the same transfection efficiency and a 1.8-fold increase in Gag-eGFP VLP production compared to shake flasks. Metabolism analysis of High Five cells indicates a reduction in the consumption of the main metabolites with respect to non-transfected cell cultures, and an increase in the uptake rate of several amino acids when asparagine is depleted. Quality assessment by nanoparticle tracking analysis and flow virometry of the VLPs produced shows an average size of 100-200 nm, in agreement with immature HIV-1 viruses reported in the literature. Overall, this work demonstrates that the High Five/TGE system is a suitable approach for the production of VLP-based vaccine candidates and other recombinant proteins

New bioconjugated rhenium carbonyls by transmetalation reaction with zinc derivatives

The transmetallation reaction between zinc dithiocarbamates and rhenium carbonyls has been used as a new strategy to link biomolecules to transition metals. The zinc(II) dithiocarbamate of isonipecotic acid (1) and the succinimidyl ester derivative (2) were prepared by straight forward procedures and were fully characterized by spectroscopic and X-ray diffraction methods, showing in both cases the presence of dinuclear complexes. Complex 2 reacted with all the primary and secondary amines studied (glycine methyl ester, β-alanine methyl ester, 1-(2-methoxyphenyl)piperazine and D-(+)-glucosamine) through the activated succinimidyl ester group, linking the metallic fragment with the biomolecule by the formation of a peptidic bond, and leading to the respective bioconjugated zinc complexes 3-6. In all cases, these zinc complexes could be isolated from the reaction medium by simple precipitation. These results evidence the potential of complex 2 to be used as a synthon to link the zinc dithiocarbamate fragment to biomolecules that contain an amine group. Complexes 3-6 were characterized by the usual spectroscopic methods and all data agree with the proposed structures, which do not contain significant interactions between the zinc fragment and the functional groups of these biomolecules. The transmetallation reaction between the zinc complexes 3-6 and the rhenium carbonyl [ReBr₃(CO)₃]²⁻ led to the expected rhenium dithiocarbamates 7-10 with no change in the organic dithiocarbamate fragments, confirming the viability of this reaction as a tool for linking biomolecules to transition elements. All complexes were characterized by spectroscopic methods and the crystal structure of 8 was studied by X-ray diffraction analysis. All data demonstrated that the biomolecule is positioned far away from the fac-{Re(CO)₃} fragment and the octahedral coordination around the metal is completed by the functionalized dithiocarbamate and a phosphine ligand. Finally, the analysis by ESI-MS spectrometry of the reaction between the zinc complex 4 and a water solution of [Re(H₂O)₃(CO)₃]+ at a very low concentration (10 ppm) showed that the transmetallation reaction took place even though the solubility of the zinc complex in water medium was as low as 0.66 ppm. This preliminary result supports the viability of this approach for the preparation of rhenium and technetium target specific radiopharmaceuticals since the preparation of these compounds are always performed in water medium

Structural changes of Arthrospira sp. after low energy sonication treatment for microalgae harvesting: elucidating key parameters to detect the rupture of gas vesicles

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The buoyancy suppression by low energy sonication (LES) treatment (0.8 W·mL-1, 20 kHz, 10 s) has recently been proposed as an initial harvesting step for Arthrospira sp. This paper aims to describe the structural changes in Arthrospira sp. after LES treatment and to present how these structural changes affect the results obtained by different analytical techniques. Transmission electron microscopy (TEM) micrographs of trichomes evidenced the gas vesicles rupture but also revealed a rearrangement of thylakoids and more visible phycobilisomes were observed. Differences between treated and untreated samples were detected by confocal microscopy, flow cytometry and optical microscopy but not by electrical impedance spectroscopy (EIS). After LES treatment, 2-fold increase in autofluorescence at 610/660 nm was measured (phycocyanin/allophycocyanin emission wavelengths) and a ten-fold decrease in side scatter light intensity (due to a reduction of trichome’s inner complexity). This was further confirmed by optical microscopy showing changes on trichomes appearance (from wrinkled to smooth).Peer ReviewedPostprint (author's final draft

Anàlisi d'alternatives per a un bioprocés de producció d'una vacuna animal

Consultable des del TDXTítol obtingut de la portada digitalitzadaEl present treball estudia el desenvolupament d'un procés per a l'obtenció d'una vacuna recombinant per a la protecció de les aus de les explotacions agropecuàries de la malaltia de Gumboro o IBD (Infectal Bursal Disease). El treball planteja estudiar diferents sistemes alternatius, fonamentalment dissenyats al voltant de diferents sistemes biològics, per tal de poder-ne fer, al final del mateix, una comparació en termes de valoració econòmica i en termes de viabilitat tecnològica, donat que aquests dos tipus d'estudis són els elements essencials a l'hora d'establir un bioprocés. El primer sistema analitzat consisteix en l'obtenció del virus IBD a partir de la infecció de cèl·lules Vero. Es tracta d'un sistema de producció d'una vacuna convencional, i que normalment requereix d'una posterior atenuació dels virus obtinguts per a la seva preparació. Aquesta aproximació està relativament estandarditzada, ja que s'aplica per a la producció de diferents tipus de vacunes, i de cara a aquest treball esdevé el sistema de referència. En els capítols següents, s'analitzen tres alternatives al procés anterior per a la producció de vacunes recombinants,en que l'agent vacunal ja no consisteix en el propi virus, sinó en una proteïna de l'embolcall del mateix virus, VP2, que ha estat identificada com a responsable de provocar una resposta immunològica adequada en els animals. S'analitza doncs, la possibilitat d'obtenir VP2 recombinant, fet que permetria desenvolupar vacunes més segures tant en la manipulació del procés com del producte en sí, i en la seva aplicació. El Capítol 5 es dedica a l'expressió de VP2 mitjançant un baculovirus recombinant mitjançant la infecció de cultius de cèl·lules d'insecte (Sf9). En el Capítol 6, s'estudia l'expressió de VP2 en cèl·lules bacterianes (Escherichia coli) i en llevats (Pichia pastoris). Tot i els esforços que s'han dut a terme en aquests sistemes només han permès expressar VP2 en E.coli mitjançant una proteïna de fusió, però sense aconseguir obtenir clons estables. Així doncs, per tal de poder valorar el potencial que podria oferir aquestes opcions, i fins i tot ajudar a valorar la necessitat de treballar-hi en més profunditat, el treball analitza i desenvolupa el sistema d'expressió basat en E.coli i P.pastoris emprant una altra proteïna recombinant com a model, ?-galactosidasa. Els sistemes de cultiu per a l'obtenció de ?-galactosidasa s'analitzen en els Capítol 7 (P.pastoris) i el Capítol 8 (E.coli). Encara que no s'hagi pogut expressar la proteïna inicialment desitjada, les dades obtingudes en aquests capítols permeten obtenir informació rellevant sobre aquests tipus de cultius, permetent realitzar l'estudi d'alternatives de bioprocés plantejat com a objectiu principal del treball. Finalment, el Capítol 9 planteja una síntesi de tot el treball, comparant les quatre alternatives de producció. La comparació és duu a terme mitjançant el plantejament d'un bioprocés a escala industrial per cada cas, dimensionant-lo en funció d'un escenari de producció comú i emprant les dades experimentals obtingudes en els respectius capítols pels diferents sistemes, i per acabar, la seva conseqüent valoració en termes econòmics. La vàlua d'aquesta anàlisi és permetre identificar la potencialitat de cadascun dels quatre bioprocessos, aportant elements molt interessants de cara a possibles preses de decisió sobre la seva possibilitat d'implementació.In the present work, the development of a production process for a recombinant vaccine against IBD (Infectal Bursal Disease), a disease that affects industrial hens and chickens, has been studied. Based on different biological systems we investigated alternative systems in order to compare them in terms of economical valuation and technical viability, two important criteria that have to be considered when establishing a bioprocess in industrial scale. The first approach undertaken was the propagation of the IBD virus by infection of Vero cells, a conventional method for vaccine production that usually requires a subsequent attenuation of the virus obtained. Since this kind of system is a relatively standardised one and already applied to the production of many different types of viruses in industrial scale, it was chosen as a reference system. The following chapters deal with the analysis of three alternative processes of recombinant vaccine production compared to the reference system. In these alternative systems the viral agent is not the virus itself, but one of its capsid proteins, VP2, that has been identified to evoke an adequate immunological response in animals. For this reason obtaining a recombinant VP2 protein would permit the development of vaccines with enhanced safety regarding process manipulation, the protein itself and its application. Chapter 5 describes the production of VP2 in the baculovirus and insect cell (Sf9) expression system. In Chapter 6, the expression of VP2 in both bacteria (E. coli) and yeast (P. pastoris) was studied. In spite of efforts to produce VP2 in both systems, it was only shown to be produced in E.coli with the help of a fusion protein. However, this was without obtaining stable clones. In order to analyse the production potential of using these expression systems, a new strategy was developed utilising ?-galactosidase as a model protein instead. The cultivation systems for the expression of ?-galactosidase are described in Chapter 7 (P. pastoris) and Chapter 8 (E.coli). Although expression of the primary desired protein was not possible, , the data obtained gave relevant information regarding this kind of production bioprocesses and may facilitate in establishing a comparative analysis of these alternative expression systems. Finally, Chapter 9 gives an overview of the study by comparing the four production strategies previously described. The comparative study was based on a large scale industrial bioprocess design. To define the industrial facility dimension, 10% of the annual demand of this vaccine in Europe was assumed in the implemention of our experimental data. The economical analysis of the feasibility ought to permit to describe the hotspots and the advantages of each alternative production system, and to overcome bottlenecks in further studies

Salisbury College Art and design

SIGLEAvailable from British Library Document Supply Centre-DSC:7168.13917(1/2001) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Bioprocess characterization of virus-like particle production with the insect cell baculovirus expression system at nanoparticle level

Altres ajuts: acord transformatiu CRUE-CSICBackground. Virus-like particles (VLPs) are a multivalent platform showing great promise for the development of vaccines, gene therapy, diagnostic, and drug delivery approaches. Particularly, HIV-1 Gag VLPs provide a robust and flexible scaffold for the presentation of a variety of antigens. The insect cell baculovirus expression vector system (BEVS) is nowadays one of the reference systems to produce these complex nanoparticles, but information about VLP quality, quantity, stability, as well as cell performance is scarce, especially at bioreactor scale. Results. VLPs produced in the reference High Five and Sf9 insect cell lines share similar physicochemical properties, with VLPs produced in Sf9 cells showing lower levels of double stranded DNA and protein contaminants, and a higher degree of VLP assembly. Besides VLPs, other nanoparticle populations are divergently encountered in each cell line. Hi5 supernatants contain a higher load of extracellular vesicles, while Sf9 supernatants exhibit higher concentrations of baculovirus particles. Similar titers are achieved when comparing Gag to Gag-eGFP VLP production, with the size of most of the nanoparticles produced comprised at the 150-250 nm range. Eventually, Gag VLP production in a 2 L stirred tank bioreactor is successfully demonstrated, validating bioprocess transference to the final product candidate. Conclusions. This work provides two potentially valuable strategies for the production of HIV-1 Gag VLPs and a detailed analysis of the different nanoparticle populations produced

New bioconjugated rhenium carbonyls by transmetalation reaction with zinc derivatives

The transmetallation reaction between zinc dithiocarbamates and rhenium carbonyls has been used as a new strategy to link biomolecules to transition metals. The zinc(II) dithiocarbamate of isonipecotic acid (1) and the succinimidyl ester derivative (2) were prepared by straight forward procedures and were fully characterized by spectroscopic and X-ray diffraction methods, showing in both cases the presence of dinuclear complexes. Complex 2 reacted with all the primary and secondary amines studied (glycine methyl ester, β-alanine methyl ester, 1-(2-methoxyphenyl)piperazine and D-(+)-glucosamine) through the activated succinimidyl ester group, linking the metallic fragment with the biomolecule by the formation of a peptidic bond, and leading to the respective bioconjugated zinc complexes 3-6. In all cases, these zinc complexes could be isolated from the reaction medium by simple precipitation. These results evidence the potential of complex 2 to be used as a synthon to link the zinc dithiocarbamate fragment to biomolecules that contain an amine group. Complexes 3-6 were characterized by the usual spectroscopic methods and all data agree with the proposed structures, which do not contain significant interactions between the zinc fragment and the functional groups of these biomolecules. The transmetallation reaction between the zinc complexes 3-6 and the rhenium carbonyl [ReBr₃(CO)₃]²⁻ led to the expected rhenium dithiocarbamates 7-10 with no change in the organic dithiocarbamate fragments, confirming the viability of this reaction as a tool for linking biomolecules to transition elements. All complexes were characterized by spectroscopic methods and the crystal structure of 8 was studied by X-ray diffraction analysis. All data demonstrated that the biomolecule is positioned far away from the fac-{Re(CO)₃} fragment and the octahedral coordination around the metal is completed by the functionalized dithiocarbamate and a phosphine ligand. Finally, the analysis by ESI-MS spectrometry of the reaction between the zinc complex 4 and a water solution of [Re(H₂O)₃(CO)₃]+ at a very low concentration (10 ppm) showed that the transmetallation reaction took place even though the solubility of the zinc complex in water medium was as low as 0.66 ppm. This preliminary result supports the viability of this approach for the preparation of rhenium and technetium target specific radiopharmaceuticals since the preparation of these compounds are always performed in water medium

Real-time and on-line monitoring of morphological cell parameters using electrical impedance spectroscopy measurements

BACKGROUND: Acquisition of electrical impedance spectroscopy (EIS) measurements enables one to obtain information about the features of cell cultures, which can be applied for real-time and on-linemonitoring purposes. RESULTS: Impedance measurements were carried out in three different cell specimens with different sizes and shapes (Vero cells, hybridoma and Escherichia coli) at different stages of cell culture, as well as during a controlled detachment process of an adherent animal cell line. The relaxation spectra obtained were fitted to a Cole impedance model and the corresponding parameters analyzed. The use of a four-electrodes measurement system decreased the dependency on the electrode interface’s impedance, and thus resulted in a systemmore sensitive to the cell features. The EISmonitoring of different cultures expansion showed the expected inverse proportional relationship between the central relaxation frequency and the cell cross-sectional area. The morphological changes of fibroblast cells during the detachment processes were also studied. Interestingly, EIS displayed the proportional relationship between the ¿ parameter of the Cole impedance model and the cell shape dispersion from sphericalmorphology (considering spherical shape ideality). CONCLUSION: The results obtained reveal the potential for developing a real-time monitoring tool for cell morphology features such as cell size and shape, which are involved inmany cellular processes like cell expansion, differentiation, cell attachment or cell death.Peer ReviewedPostprint (author's final draft