The glycosylation pattern of an antibody determines its clinical performance, thus industrial and academic efforts to control glycosylation persist. Since typical glycoengineering campaigns are time- and labor-intensive, the generation of a rapid protocol to characterize the impact of glycosylation genes using transient silencing would prove useful.
Recombinant monoclonal antibodies bind specific molecular targets and, subsequently, induce an immune response or inhibit the binding of other ligands. However, monoclonal antibody functionality and half-life may be reduced by the type and distribution of host-specific glycosylation. Attempts to produce superior antibodies have inspired the development of genetically modified producer cells that synthesize glyco-optimized antibodies. Glycoengineering typically requires the generation of a stable knockout or knockin cell line using methods such as clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9. Monoclonal antibodies produced by engineered cells are then characterized using mass spectrometric methods to determine if the desired glycoprofile has been obtained. This strategy is time-consuming, technically challenging, and requires specialists. Therefore, an alternative strategy that utilizes streamlined protocols for genetic glycoengineering and glycan detection may assist endeavors toward optimal antibodies. In this proof-of-concept study, an IgG-producing Chinese hamster ovary cell served as an ideal host to optimize glycoengineering. Short interfering RNA targeting the Fut8 gene was delivered to Chinese hamster ovary cells, and the resulting changes in FUT8 protein expression were quantified. The results indicate that knockdown by this method was efficient, leading to a ~60% reduction in FUT8. Complementary analysis of the antibody glycoprofile was performed using a rapid yet highly sensitive technique: capillary gel electrophoresis and laser-induced fluorescence detection. All knockdown experiments showed an increase in afucosylated glycans; however, the greatest shift achieved in this study was ~20%. This protocol simplifies glycoengineering efforts by harnessing in silico design tools, commercially synthesized gene targeting reagents, and rapid quantification assays that do not require extensive prior experience. As such, the time efficiencies offered by this protocol may assist investigations into new gene targets.
N-linked glycosylation is an enzymatic process by which oligosaccharide moieties are covalently linked to Asn residues. Unlike de novo protein synthesis, glycan synthesis is a non-templated reaction that results in heterogeneous glycosylation of proteins. The structure, composition, and distribution of glycans can affect protein conformation and function. Indeed, N-glycosylation in the crystallizable fragment (Fc) region of immunoglobulin G (IgG) regulates the therapeutic efficacy, immunogenicity, and half-life of the antibody1. As such, the quality by design (QbD) paradigm for the development of recombinant biotherapeutic protein products naturally identifies glycosylation as a critical quality attribute (CQA)2,3. Mammalian cells are often the preferred expression systems as they inherently produce human-like glycosylation patterns more closely than bacteria, yeast, insect, or plant cells. Moreover, Chinese hamster ovary (CHO) cells are selected over other mammalian cell lines because they are resistant to human virus infection, secrete products at high titers, and can be grown in suspension culture to high viable cell densities4. With respect to glycan formation, non-CHO murine production cells generate immunogenic glycans (α(1-3)-linked galactose [α(1-3)-Gal] and N-glycolylneuraminic acid [NeuGc]) that impinge on the safe use of monoclonal antibodies (mAbs)5. These benefits make CHO cells the foremost expression system, responsible for the production of over 80% of new biotherapeutics between 2014 and 20186. However, template-independent glycosylation is a conserved mechanism that leads to CHO-derived biotherapeutics with an array of glycoforms.
Biotherapeutic development strategies aim to control heterogeneity in CHO cells by genetic engineering. Some literature examples include the knockdown of sialidases (Neu1, Neu3)7, GDP-mannose 4,6-dehydratase (GMD) knockout8, and overexpression of glycosyltransferases (GnTIII)9. Advances in glycoengineering are possible due to a combination of publicly available resources, like the CHO genome10, and the ongoing development of genetic engineering tools, such as transcription activator-like effector nucleases (TALENs), zinc finger nucleases (ZFNs), and clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (CRISPR-Cas9)11,12,13,14. These tools are typically delivered to CHO cells as plasmid DNA or as purified ribonucleoprotein (RNP) complexes. Conversely, RNA interference (RNAi) is a genetic engineering technology that, in its simplest form, only requires the delivery of purified short interfering RNA (siRNA) oligonucleotides. Endogenous proteins process double-stranded siRNA into single strands, and the nuclease, RNA-induced silencing complex (RISC), forms a complex with siRNA to cleave target mRNA sequences15,16,17. Gene silencing via this method is transient due to RNA instability, but the investigation herein leverages this feature to assist rapid screening.
The model enzyme selected for the current study, α1,6-fucosyltransferase (FUT8), produces N-glycans with α-1,6 core-linked L-fucose (Fuc). This modification is a primary determinant of antibody-dependent cell cytotoxicity (ADCC) activity, as evidenced by studies of commercial antibodies. In the absence of core fucosylation, Rituximab (anti-CD20 IgG1) increases ADCC 50-fold and increases ADCC in Trastuzumab (anti-Her2 IgG1) by improving FcgRIIIa binding18,19. Core fucosylation is, thus, considered an undesirable feature of mAbs that warrants efforts to reverse this phenotype. There are examples of successful Fut8 gene targeting using siRNA with concomitant increases in ADCC20,21,22, albeit these examples deliver Fut8 siRNA encoded on plasmid DNA. Such experiments generate stable gene silencing as plasmid DNA serves as a template for siRNA synthesis. This allows cells to replenish siRNA molecules that are degraded by intracellular RNases and phosphatases. Conversely, the delivery of exogenous synthetic siRNA only permits transient gene silencing as siRNA cannot be replenished due to the lack of an intracellular template. Thus, users should consider if experimental designs are compatible with plasmid-derived or synthetic siRNA. For example, studies focused on peak mAb production, typically day six of the culture23,24, may opt for synthetic siRNA that can be delivered to cells a few days before peak expression. The benefits of a transient approach using synthetic siRNA include the ability to outsource production and the fact that multiple siRNA constructs can be generated in a fraction of the time taken to generate constructs in plasmids. Furthermore, synthetic siRNA is efficacious, as evidenced by literature examples of Fut8 gene silencing that are sufficient to reduce FUT8 protein expression25 and yield afucosylated IgGs with increased FCgRIIIa binding and ADCC26.
The success of this glycoengineering protocol was determined by the degree of Fc glycosylation. Mass spectrometry is normally the method of choice for glycomic analyses; however, capillary gel electrophoresis and laser-induced fluorescence detection (CGE-LIF) is perfectly amenable to resolving the glycoprofile of purified IgGs and has the advantage of greater rapidity and simplicity. Mass spectrometry protocols must combine the appropriate chromatographic and derivatization methods, ionization sources, and mass analyzers27,28,29. In addition to requiring a trained specialist, mass spectrometry protocols are lengthy, and the diversity of methods makes data difficult to compare between laboratories with different setups. In the context of biopharmaceuticals, CGE-LIF is a sensitive method that can provide sufficient details of an antibody glycoprofile and is easily scalable for high-throughput methods. For low abundance, highly complex mixtures with poorly characterized glycoproteins, the advantages of mass spectrometry might remain. However, the high-resolution and high-sensitivity mAb analytics afforded by CGE-LIF-based N-glycan analysis serve as a rationale to trial this method. Furthermore, sample preparation and analysis are complete in just a few hours30. Recent studies have shown that CGE-LIF can be used to monitor glycans derived from human plasma31, mouse32, and CHO IgGs33. These studies highlight the use of CGE-LIF for high-throughput sample analysis and small sample volumes.
The CGE-LIF method has limitations that should be taken into consideration. Cost is a significant barrier to the use of this and other devices for glycan analysis. However, these costs are typical within the field, and CGE-LIF is thought to be a cost-effective option34. Labs with smaller budgets may find it more practical to lease machinery or outsource samples analysis. Another consideration of any analytical method is repeatability. Evaluation of CGE-LIF was conducted using 48 replicates of the same sample that were assayed on different days. The relative standard deviation per capillary was determined for intrabatch and interbatch repeatability. The intrabatch comparison of replicates was found to have a relative standard deviation of 6.2%, indicating that capillary performance is not uniform. Further, a comparison of interbatch data showed a relative standard deviation of 15.8%31, indicating that the capillary performance changes over time. The operational shortcomings identified may not apply in the current study, which uses different machinery and proprietary reagents. If users intend to develop an in-house protocol, it would be worth considering the study by Ruhaak et al.31, which carefully evaluated the reagents for CGE-LIF. As such, the reagents for sample injection (Hi-Di Formamide and DMSO), glycan labeling (NaBH3CN or 2-picoline borane)31, and others have been optimized.
This study presents a time-efficient glycoengineering protocol that combines the rapidity of direct RNAi with downstream glycomic analysis. The methodology is illustrated using the Fut8 gene as a target for the reasons outlined above.
1. DsiRNA design and reconstitution
DsiRNA target | Sequence | GC (%) | ||
Structure A | 5' GAGAAGAUAGAAACAGUCAAAUACC 3' | 36% | ||
5’ GGUAUUUGACUGUUUCUAUCUUCUCUC 3' | ||||
Structure B | 5' AGAAUGAGAAUGGAUGUUUUUCCTT 3' | 32% | ||
5' AAGGAAAAACAUCCAUUCUCAUUCUGA 3' | ||||
Structure C | 5' AGAGAAGAUAGAAACAGUCAAAUAC 3’ | 32% | ||
5' GUAUUUGACUGUUUCUAUCUUCUCUCG 3' |
Table 1. DsiRNA sequences used for Fut8 knockdown. Sequences generated by IDT that target Fut8 in Chinese hamster and CHO K1 cell genomes. The sense and antisense sequences for each construct are shown (respectively), and the GC content of each structure is displayed. Reprinted from Kotidis et al.52.
2. DsiRNA transfection
3. IgG quantification and purification
4. Buffer exchange and sample concentration
5. Glycan analysis
6. Western blot
Western blot analysis showed reduced FUT8 protein expression in cells transfected with a mixture of three Fut8 DsiRNA constructs. In control samples transfected with non-targeting DsiRNA, FUT8 appeared as a double band at ~65 and 70 kDa. Since the predicted molecular weight of FUT8 is 66 kDa, a reduction in the signal intensity of the lower molecular weight band is indicative of gene silencing. To confirm and quantify gene silencing, the level of FUT8 protein was normalized to the relative GAPDH protein level. Western blot analysis detected two bands for GAPDH at ~37 and 35 kDa. The higher molecular weight band corresponds to the predicted protein size and is, therefore, used in normalization calculations. When normalized against GAPDH protein levels, FUT8 protein expression was reduced by up to 60% (Figure 1).
In line with the observation of gene knockdown at 48 h post transfection, corresponding mAb samples were processed for analysis by CGE- LIF. Glycan structures from knockdown cells showed a decrease in fucosylation. This trend was most pronounced in agalactosylated structures (G0F) and observed to a lesser extent in galactosylated structures (G1F, G1F' and G2F). From this dataset, the total IgG core fucosylation decreased to ~75%, down from ~95% core fucosylation observed for the negative control condition (Figure 2). A greater reduction in core fucosylation was anticipated given the ~60% decrease in FUT8 protein levels. Upon reflection, it is noteworthy that the glycoprofile represents glycosylated mAbs that accumulated over a period of 48 h since transfection, while gene silencing represents protein levels present at the time of harvesting only.
Further scrutiny of this knockdown method involved varying the DsiRNA concentration, harvest time, and electroporation conditions. Each factor was individually probed to determine its relevance. The impact of electroporation pulse conditions on core fucosylation and cell viability is captured in Experiments B, C, D, and E. These results demonstrate a two-fold reduction in core fucosylation from electroporation using two square wave pulses (Experiment C) compared to a single square wave pulse (Experiment B), without significant differences in cell viability (Table 2). Electroporation condition e3 (Experiment D) led to the lowest cell viability (~90%) and IgG yield at this timepoint. However, cells that survived the electroporation event were moderately transfected, as evidenced by the ~10% decrease in core fucosylation (Table 2). Interestingly, Experiment D used electroporation conditions that provided the greatest reduction in core fucosylation (14.7%) but were evidently detrimental to cell viability (91%-93% viability). This limited set of experiments illustrates the need to determine electroporation settings that enable sufficient permeabilization of the cell membrane without causing irrevocable damage. It is also interesting to note the role of siRNA concentration and harvest time on core fucosylation. Overall, increasing siRNA concentration has a greater influence on core fucosylation than increasing the harvest time (Experiments B, F, G versus Experiments A, B, H). In future experiments, it would be interesting to titrate the siRNA concentrations delivered by the electroporation method e2.
Figure 1. Experimental flow chart. Glycoengineering and sample analysis steps are depicted with the associated time required for each step. SiRNA design takes a few hours, depending on the number of gene targets or constructs per gene target. CHO cell transfection with siRNA is complete in a few hours, and transformed cells are left to grow for 48 h. Cell pellets and supernatants are harvested within a few hours. Cell pellets are lysed, and the intracellular proteins are separated on an SDS PAGE and subsequently blotted and probed with antibodies against the target gene. Glycans are cleaved from purified antibodies and analyzed by CGE-LIF. These assays may require 1 day each. Please click here to view a larger version of this figure.
Figure 2. Confirmation of RNA interference. Western blot detection of α-1,6-fucosyltransferase (FUT8) protein levels in samples treated with Fut8 or non-targeting control DsiRNA. Bands corresponding to FUT8 are more intense in control than Fut8 knockdown samples. The GAPDH protein level was also assessed in order to normalize target gene expression. All samples were taken from Experiment G (see Table 2). Reprinted from Kotidis et al.52. Please click here to view a larger version of this figure.
Figure 3. Effect of Fut8 knockdown on cumulative IgG glycosylation at 48 h. A shift in glycan distribution is detected in knockdown samples. In particular, the relative abundance of the main core-fucosylated structures (G0F) is reduced while the afucosylated species are increased in the knockdown experiment. Measurements were performed from Experiment G samples (see Table 2). Biological triplicates performed for each experiment were mixed after harvesting to reduce the burden of downstream analysis. Reprinted from Kotidis et al.52. Please click here to view a larger version of this figure.
Experiment name | Electroporation method | DsiRNA concentration (nΜ) | Harvest time (h) | Viability (%) | Xv (106 cells·mL-1) | IgG titer (mg·L-1) | Difference in core-fucosylation (%) | ||||||
ExpA_Negative | e1 | 500 | 24 | 98.3 | 4.71 | 122.5 | – | ||||||
ExpA_Knockdown | e1 | 500 | 24 | 98.3 | 4.9 | 110.3 | 4.08 | ||||||
ExpB_Negative | e1 | 500 | 48 | 95.6 | 9.55 | 453.3 | – | ||||||
ExpB_Knockdown | e1 | 500 | 48 | 96.7 | 9.61 | 469 | 5.38 | ||||||
ExpC_Negative | e2 | 500 | 48 | 96.3 | 9.91 | 449.3 | – | ||||||
ExpC_Knockdown | e2 | 500 | 48 | 96.7 | 11 | 454.6 | 11.42 | ||||||
ExpD_Negative | e3 | 500 | 48 | 90.6 | 6.25 | 318.5 | – | ||||||
ExpD_Knockdown | e3 | 500 | 48 | 89.1 | 6.09 | 311.85 | 9.71 | ||||||
ExpE_Negative | e4 | 500 | 48 | 91.1 | 7.2 | 380.3 | – | ||||||
ExpE_Knockdown | e4 | 500 | 48 | 93.3 | 7.79 | 422.8 | 14.7 | ||||||
ExpF_Negative | e1 | 750 | 48 | 96.2 | 9.7 | 501 | – | ||||||
ExpF_Knockdown | e1 | 750 | 48 | 95.7 | 9.76 | 504.6 | 9.9 | ||||||
ExpG_Negative | e1 | 1000 | 48 | 96.1 | 11.1 | 422.6 | – | ||||||
ExpG_Knockdown | e1 | 1000 | 48 | 95.9 | 9.73 | 499.3 | 17.26 | ||||||
ExpH_Negative | e1 | 500 | 72 | 94.4 | 14.3 | 925.8 | – | ||||||
ExpH_Knockdown | e1 | 500 | 72 | 95 | 13.5 | 1018.4 | 7.37 |
Table 2. Transfection optimization. Iterative modifications of the electroporation method, DsiRNA concentration, and harvest time led to changes in cell viability, viable cell density, IgG titer at the harvest time, and differences in core fucosylation. Each experiment compared the knockdown and the respective negative control to determine if the modification produces the desired effect (i.e., a decrease in fucosylation). Electroporation settings were as follows: e1: 1200 V, 0.1 ms, square waveform; e2: 1200 V, 2x 0.1 ms, 5 s between pulses, square waveform; e3: 150 V, 20 ms, square waveform; e4: 250 V, 500 μF, exponential decay. Reprinted from Kotidis et al.52.
Glycosylation pathways involve a complex metabolic network of enzymes and accessory proteins. Dissecting the function of pathway constituents is daunting if reliant on conventional knockout or knockin genetic engineering strategies alone. An alternative approach is to preliminarily screen members of a pathway using a transient loss-of-function assay. To this end, two rapid protocols were combined, RNAi and CGE-LIF detection, to create a more efficient way to characterize glycosylation genes. The method described requires 5-7 days for completion compared to conventional methods that potentially take several weeks for completion. Further, research environments with automation capabilities could exploit this method to screen more gene candidates than feasible with manual handling.
The success of a transient glycoengineering campaign is largely dependent on the siRNA design. Custom DsiRNA designs must follow the rules previously outlined, or for ease, users may opt for commercially available predesigned sequences. Like other gene modification strategies, RNAi has the potential for off-target effects. Therefore, users are encouraged to assess unintentional gene targeting by computational methods41. Experimental design choices can also help limit off-target effects. Kittler et al. showed that the multiplexed delivery of siRNA led to a reduction in off-target effects42. Although this seems counterintuitive, it is suggested that a master mix reduces the concentration of each siRNA construct, thus limiting the opportunity for off-target gene silencing. A further benefit is that the simultaneous transfection of siRNA structures that target the same gene increases the likelihood of successful RNAi. The use of a master mix also ensures consistency between samples and replicates and speeds up the transfection process. Following an initial screen of mixed siRNA constructs, another experiment may be conducted using individual constructs to ascertain the RNAi efficiency of each sequence. In this and other knockdown studies, up to three siRNA have been pooled and delivered to cells43,44,45. However, it may be desirable to screen more than three siRNA simultaneously to efficiently target a single gene or to target several genes. Indeed, one study demonstrated multiplexed siRNA-mediated silencing of up to six genes at levels comparable to the silencing of individual genes46. However, further studies are needed to determine the maximum number of siRNA constructs that can be used in a pool without compromising the silencing efficiency. The multiplex strategy was proposed by Martin et al. to enhance the pace of RNAi library screening experiments46, and a similar concept may prove useful to screen glycosylation genes.
The protocol described herein serves as a proof-of-concept with the expectation that subsequent experiments will be performed to validate other glycosylation genes. New genes of interest may be uncharacterized or less popular than Fut8, and primary antibodies to detect gene silencing may be poor or unavailable. In this scenario, alternative methods such as RT-PCR may be used to quantify gene silencing47, but it should be noted that RT-PCR detects mRNA rather than protein. When antibodies for western blotting are available, a common issue is poor detection or the presence of non-specific bands. Troubleshooting guides to help users solve common issues are available, and these tend to include a range of solutions such as primary antibody titration, alternative blocking, and detection conditions48,49. In this study, FUT8 unexpectedly appeared as a double band at ~65 and ~70 kDa. It is possible that the ~70 kDa band represents glycosylated FUT8. Literature evidence from human cell lines describes O-linked glycosylation at Thr 56450,51, a site that is conserved in Chinese hamster, and CHO K1 FUT8 sequences.
As previously mentioned, glycosylation pathways often involve a complex array of enzymes. The current protocol has been developed, optimized, and demonstrated using a monogenic glycosylation reaction controlled by Fut8. Therefore, further studies are required to confirm the robustness of this method when the target gene encodes an enzyme with alternate kinetics and expression levels or a pathway regulated by isoenzymes with redundant functions.
Taken together, the ability to rapidly silence genes and detect modified IgG glycoprofiles is a useful tool in the effort toward custom glycoengineered antibodies. Insights from similar short-term studies can be applied to generate stable glycoengineered cells for use in long-term assays like fed-batch culture. Outside of the pharmaceutical context, this method contributes toward the study of glycan biology and highlights the important function of glycans in development, health, and disease.
The authors have nothing to disclose.
PK thanks the Department of Chemical Engineering, Imperial College London, for his scholarship. RD thanks the U.K. Biotechnology and Biological Sciences Research Council for his studentship. MM is funded by the U.K. Biotechnology and Biological Sciences Research Council (Grant reference: BB/S006206/1). IAG thanks the Irish Research Council (Scholarship No. GOIPG/2017/1049) and CONACyT (Scholarship No. 438330).
32 Karat software | SCIEX | contact manufacturer | Software for glycan data acquisition and analysis using the Fast Glycan analysis protocol and separation method. |
Acetonitrile, HPLC grade | Sigma Aldrich | 34851 | Solvent. |
Anti-FUT8 antibody | AbCam | ab198741 | Rabbit polycloncal to Fut8. Use this antibody to quantify Fut8 protein expression; replace this antibody if using siRNA targeting a different gene. |
Anti-GAPDH antibody | AbCam | ab181602 | Rabbit monoclonal to GAPDH. Alternative housekeeping genes exist and might be preferred by the user. |
BioDrop Spectrophotometer | Biochrom | 80 3006 55 | Instrument used to quantify protein concentration. |
BLItz | ForteBio | 45 5000 | Instrument. Label-Free Protein Analysis System. |
BRAND Haemocytometer | Sigma Alrich | BR717810 | Counting chamber device |
Capillary cartridge | SCIEX | A55625 | Pre-assembled capillary cartridge with window (30 cm total length, 375 µm outer diameter (o.d), x 50 µm inner diameter (i.d). |
C100HT Glycan analysis—capillary electrophoresis | SCIEX | contact manufacturer | Capillary gel electrophoresis instrument, the CESI 8000 Plus instrument is now used. |
CD CHO Medium | Thermo Fisher Scientific | 10743029 | Replace this with a culture medium appropriate for the cell line of choice. |
Centrifuge tubes, 15 mL | Greiner Bio | 188261 | Sterile polypropylene tube. |
Centrifuge tubes, 50 mL | Greiner Bio | 227270 | Sterile polypropylene tube. |
CHO IgG | MedImmune | Gift | Chinese Hamster Ovary cells expressing an IgG monoclonal antibody (CHO T127). Created using the GS system. |
Dulbecco's phosphate-buffered saline (DPBS) | Gibco | 14190144 | 1x PBS, without calcium or magnesium. |
Erlenmeyer Flasks with Vent Cap, 125 mL | Corning | 431143 | Replace this with a culture vessel suitable for growing the cell line of choice. |
Erlenmeyer Flasks with Vent Cap, 250 mL | Corning | 431144 | Replace this with a culture vessel suitable for growing the cell line of choice. |
Fast Glycan Labelling and Analysis kit | SCIEX | B94499PTO | Labels N-glycans with APTS and then uses a magnetic-bead based clean up system to remove excess APTS. |
Fut8 DsiRNA | IDT | Custom | Custom designed DsiRNA targetting Fut8. |
Gene Pulser cuvettes, 0.4 cm | Bio-Rad | 1652088 | Electroporation cuvette. |
Gene Pulser Xcell Eukaryotic System | Bio-Rad | 165 2661 | Insturment. Xcell main unit with Capacitance Extender (CE) Mocdule and ShockPod. |
Immobilon-FL PVDF membrane | Merck-Millipore | IPFL00010 | Immunoblot transfer membrane, low background. |
L-Methionine sulfoximine (MSX) | Sigma Aldrich | M5379 | Only necessary for CHO cell lines using the glutamine synthetase (GS) selection system. |
Kimwipes | Thermo Fisher Scientific | 10623111 | Low-lint, high absorbency and chemically inert wipes. |
M-PER Mammalian Protein Extraction Reagent | Thermo Fisher Scientific | 78505 | Alternative lysis buffers such as RIPA are also appropriate. |
Methanol, HPLC grade | Fisher Scientific | 10365710 | Solvent. |
Microcentrifuge tubes, 1.5 mL | Eppendorf | 616201 | Autoclavable tubes. |
Mini-PROTEAN Tetra Vertical Electrophoresis Cell system | Bio-Rad | 1658035FC | Instrument. 4-gel capacity, for 1.0 mm thick handcast gels, with Mini Trans-Blot Module and PowerPac HC Power Supply. |
NC-Slide A8 | ChemoMetec | 942 0003 | 8-chamber slide for use with NucleoCounter NC 250. |
Negative Control DsiRNA, 5 nmol | IDT | 51 01 14 04 | Non-targeting DsiRNA. |
Nuclease-free duplex buffer | IDT | 11-01-03-01 | Reconstitution buffer for DsiRNA. |
NucleoCounter NC-250 | Chemometec | contact manufacturer | Instrument. Automated Cell Analyzer |
Page-Ruler ladder, 10 to 180 kDa | Thermo Fisher Scientific | 26616 | Mixed blue, orange and green protein standards for SDS PAGE and western blotting. |
PCR tubes | Greiner Bio | 608281 | Autoclavable tubes for DsiRNA aliqouts and glycan preparation. |
Pipette filter tips sterilised (10, 200, 1000 µL) | Gibson | F171203, F171503, F171703 | Sterile filter tips to avoid RNA contamination. |
PNGase F enzyme | New England Biolabs | P0704S | Enzymatic cleavage of glycans from glycoproteins. |
Polypropylene columns, 1 mL | Qiagen | 34924 | Columns for gravity-flow chromatography. |
Protease Inhibitor Cocktail | Sigma Aldrich | P8340 | Inhibition of serine, cysteine, aspartic proteases and aminopeptidases |
Protein-A Agarose Beads | Merck-Millipore | 16 125 | For purification of human, mouse and rabbit immunoglobulins. |
Protein-A biosensor | ForteBio | 18 5010 | Tips functionalised with Protein A for rapid antibody quantification. |
RNaseZap | Invitrogen | AM9780 | Removes RNAse contamination. |
Sample dilutent | ForteBio | 18 1104 | Activate Protein A tips. |
Serological pipets (5, 10, 25 mL) | Corning | 4487, 4488, 4489 | Used for sterile cell culture tecniques. |
Sodium cyanoborohydride solution 1 M in THF | Sigma Aldrich | 296813 | Reducing agent. |
Solution 18 | ChemoMetec | 910-3018 | Staining reagent containing acridine orange (AO) and 4',6-diamidino-2-phenylindole (DAPI) |
Spin-X Centrifuge Tube Filters | Corning | 8161 | 0.22 µm pore, Cellulose Acetate membrane. |
Suspension plate with lid, 6-well | Greiner Bio | 657 185 | Hydrophobic culture plate for growth of suspension cultures. |
Syringe filters, 0.22 μm | Sartorius | 514 7011 | Surfactant-free cellulose acetate (SFCA) |
Syringes with Luer lock tip, 20 mL | Fisher Scientific | 10569215 | For secure connection with syringe filter. |
Trypan Blue solution | Gibco | 15250061 | Stains dead and dying cells. |
Vivaspin 500, 3,000 MWCO | Sartorius | VS0191 | Polyethersulfone |
WesternBreeze Chromogenic Kit, anti-rabbit | Thermo Fisher Scientific | WB7105 | Western blot detection kit, alternative blocking buffers and antibody diluents can be made by the user using recipes available online. |