mRNA-LNP

Preparation work that readies the 'template' for the transcription reaction known as IVT. The circular plasmid, the blueprint, is cut at just 1 site around the ring with a restriction enzyme and opened into a single linear DNA.

If any is left uncut, transcription goes once around the template (read-through), generating overlong products and double-stranded RNA. Gel electrophoresis confirms the linearization rate and the amount of circular plasmid that remains.

In other words, this step judges 'was it cut properly at only 1 site?' before release. If this is sloppy, impurities in later steps increase sharply, so it serves as the first quality gate.

The template for IVT is a circular plasmid cut at just 1 site with a restriction enzyme to make it linear. If linearization is incomplete, transcription goes around the plasmid (read-through), causing overlong transcripts and double-stranded RNA. So before release, confirm 'was it cut properly?' and 'how much supercoiled plasmid remains?'

Alternatives in practice

• Assessment of linearization rate/template integrity by qPCR · Applied Biosystems QuantStudio 5/Bio-Rad CFX Opus 96 + PowerUp SYBR Green Master Mix — Quantifies undigested (residual supercoiled) template with primers spanning the cut junction. Trace-level, high sensitivity.
• Purification of linearized plasmid by preparative chromatography/precipitation · Cytiva ÄKTA pure 150 + HiScreen/HiTrap Q anion exchange, or ethanol/PEG precipitation — Removes enzyme, buffer and cut-off pieces, doubling as pre-IVT purification.
• Concentration and purity confirmation by UV absorbance · Thermo NanoDrop One/Implen NanoPhotometer N60 — Screens for residual protein and organic matter by A260/A280 and A260/A230. Simple, but cannot determine the linearization rate.

This is the heart of the process, where the mRNA itself is made. An enzyme called T7 (or SP6/T3) links the 4 raw materials (NTPs) into a single strand using linear DNA as the template, synthesizing mRNA.

Yield, integrity and the amount of double-stranded RNA by-product all change with Mg2+ concentration, NTP ratio and reaction time. Progress is monitored in nearly real time by AEX-HPLC.

The point is judging 'when to stop.' Quality varies whether the reaction is pushed too far or stopped too early, so the call to end the reaction at the optimal moment is made while watching the data.

T7 (or the related SP6/T3) RNA polymerase synthesizes mRNA from 4 NTPs using linear DNA as the template. Yield, integrity and the amount of dsRNA change with Mg2+ concentration, NTP ratio and reaction time, so the progress of the reaction is watched in close to real time to decide when to stop.

Alternatives in practice

• Lateral flow/rapid IPC · Commercial simple RNA detection strips + handheld reader — An ultra-rapid in-process check at the level of presence/absence. Low quantitation.
• Time-course UV (A260) measurement · Thermo NanoDrop One/Agilent Cary 60, or in-line UV-Vis probe — Tracks the increase in mRNA concentration over time. Simple, but purity and integrity require separate testing.
• co-transcriptional capping (cap added simultaneously with IVT) · The T7 IVT system above + TriLink CleanCap Reagent AG [N-7113] — Omits the enzymatic capping step. AEX-HPLC monitoring is the same.

A step that puts a 'cap', like a hat, on the front end (5' end) of the synthesized mRNA. With this hat, the mRNA is easily translated in the cell and is less likely to be regarded as foreign by the immune system.

A bare mRNA without the hat works poorly and also triggers inflammation. So it is not enough that the cap is attached; 'what percent was correctly attached' must be pinned down as a number.

LC-MS identifies the cap structure (mainly Cap1) and quantifies capping efficiency. It is an unglamorous but indispensable finishing move that affects efficacy and safety.

When a cap (the Cap1 structure is mainstream) is attached to the 5' end of mRNA, it is easily translated in the cell and is less likely to be treated as foreign by innate immunity. mRNA without a cap works poorly and causes inflammation, so 'what percent was correctly capped' is measured.

Alternatives in practice

• Capping efficiency assay by ribozyme/DNAzyme · The IP-RPLC-UV system above (Agilent 1290 Bio LC) — Calculates capping efficiency from the relative ratio of 5' fragments by UV detection without using MS.
• Vaccinia-based enzymatic capping + 2'-O-methylation (conversion to Cap1) · NEB Vaccinia Capping System [M2080] + 2'-O-MTase [M0366], temperature-controlled reaction system — Enzymatic Cap1 addition when co-transcriptional capping is not used.
• 5' fragment profiling by IP-RP-UHPLC/UV · Waters ACQUITY Premier + Oligonucleotide BEH C18 column, UV detection — For labs without MS. Separates and quantifies capped/uncapped fragments by retention time.

The reaction liquid after transcription still contains the DNA used as the template. This step breaks it down finely with an enzyme called DNase I and removes it.

This treatment serves 2 purposes: (1) to stop the transcription reaction properly, and (2) to reduce residual DNA, which would be a safety risk if left in the final product.

After degradation, qPCR measures the amount of residual DNA to confirm it is within specification. It is the step at the entrance of purification that 'erases the template and closes the reaction.'

When IVT is finished, the template DNA is degraded and removed with DNase. This stops the reaction and reduces residual DNA that would be mixed into the final product. Residual DNA is a safety-related impurity, so it is quantified later and kept within specification.

Alternatives in practice

• Residual DNA quantitation with a fluorescent dye (PicoGreen) · Fluorescence plate reader (BMG CLARIOstar/Molecular Devices SpectraMax) + Thermo Quant-iT PicoGreen dsDNA [P11496] — Simple quantitation of total dsDNA. No sequence specificity, and pretreatment is needed in the presence of mRNA.
• Immunoassay-based residual DNA measurement · ELISA/plate reader method succeeding the Thermo Threshold system — Specific detection of host/plasmid DNA. For orthogonal confirmation of qPCR.
• Physical DNA removal by downstream chromatography/TFF · Cytiva ÄKTA process + oligo-dT/AEX, or hollow fiber TFF (ÄKTA flux) — Removes fragmented DNA by differences in size/affinity without relying on enzymatic degradation.

Prep work before the main capture purification. The reaction liquid after DNase treatment is rich in NTPs, short fragments, salts and enzymes, and as it is, binding to the resin does not go well.

So the liquid is concentrated and its buffer replaced by TFF (ultrafiltration/diafiltration) or salt precipitation. The idea is to lower conductivity and drop interfering small molecules in advance.

The aim is to stabilize the 'binding efficiency and reproducibility' of the next capture step. It is a preparatory step for standardization, making the conditions of the loaded liquid the same every time.

The IVT reaction liquid after DNase treatment has high conductivity and contains large amounts of free NTPs and small molecules, which impair the binding efficiency and reproducibility of capture by oligo-dT or ion exchange. Standardizing the loading conditions by buffer exchange with TFF (or concentration and desalting by precipitation) before the capture step is a standard process step.

Alternatives in practice

• Concentration and desalting by LiCl/ammonium acetate precipitation · Refrigerated centrifuge (Beckman Coulter Avanti J-15R) + LiCl/ammonium acetate reagents — For small scale and lab use. Large-scale salt removal requires redissolution and washing.
• Concentration and diafiltration by flat-sheet cassette TFF · Sartorius Sartoflow Smart/Cytiva ÄKTA readyflux + Sartocon Hydrosart 100 kDa/Merck Pellicon 3 Ultracel 100 kDa — High flux with flat sheet instead of hollow fiber. Watch for shear sensitivity.

The core of mRNA purification. The poly(A) tail at the end (3' end) of the mRNA is likened to a 'fishhook,' and a resin that grabs it picks out only full-length mRNA.

Resin lined with dT (thymidine) sticks only to poly(A), so NTPs, incomplete chains cut partway and enzymes can be washed away together. Only the target molecule remains.

Because it uses poly(A), the 'proof of the real thing,' the selection is smart and highly reproducible. It is the separation step that plays the lead role in downstream processing in many mRNA manufacturing processes.

The poly(A) tail at the 3' end of mRNA is used as a 'fishhook.' A resin lined with dT grabs only poly(A), so NTPs, short incomplete chains and enzymes are washed away together and only full-length mRNA is recovered. It is the core step of mRNA purification.

Alternatives in practice

• Preparative purification by ion-pair reverse-phase HPLC (IP-RP) · Agilent 1290 Infinity II Bio LC/preparative LC + DNAPac RP, TEA/HFIP mobile phase — Separates full-length product from impurities independent of poly(A). Scale-up and solvent load are the challenges.
• Core/multimodal chromatography · Cytiva ÄKTA process+Capto Core 700/Capto adhere, or BIA Separations (Sartorius) CIMmultus QA/oligo-dT monolith — Monoliths are advantageous for mass transfer of large mRNA molecules. They also allow simultaneous clearance of dsRNA/fragments.
• mRNA enrichment and purification by cellulose/ethanol treatment · Cellulose column (Sigma cellulose powder) + ethanol buffer — Simple and low-cost, but selectivity is inferior to affinity resin. Reduction of dsRNA is also expected.

A step that targets and removes the double-stranded RNA (dsRNA) born as a by-product of IVT. dsRNA triggers a strong innate immune response, lowering efficacy and causing adverse reactions.

The troublesome part is that its size is close to that of the mRNA itself. It passes through together with the mRNA in TFF or ordinary purification, so a dedicated removal step using cellulose or the like is needed.

After removal, it is quantified accurately with the anti-dsRNA antibody called J2. 'Managing a hard-to-remove impurity with a dedicated hand and a dedicated yardstick' is a step directly tied to safety.

dsRNA formed as a by-product of IVT triggers a strong innate immune response, lowering efficacy and causing adverse reactions. Its size is close to that of the mRNA itself, so it is hard to remove by TFF or simple purification, and a dedicated removal step and precise quantitation are required.

Alternatives in practice

• dsRNA quantitation by RP-UHPLC/UV · Thermo Vanquish/Waters ACQUITY Premier + Oligonucleotide BEH C18, heated separation — Quantifies the dsRNA peak from retention time differences without antibody. High throughput.
• dsRNA detection by biolayer interferometry (BLI) · Sartorius Octet R8/BLI + J2 antibody-immobilized biosensor — Label-free and real-time. For in-process monitoring.
• Qualitative confirmation by dot blot/immunoblot · Bio-Rad ChemiDoc MP+J2 antibody (Nordic-MUbio) — Simple pass/fail screening. Semi-quantitative.

A finishing step that readies the purified mRNA to be handed to the next step. Salts, small molecules and leftover ethanol are removed and the material is brought to the target concentration and composition.

The method is TFF (ultrafiltration/diafiltration). While the mRNA is retained by the membrane, unneeded small molecules are washed away, and the material is concentrated while being exchanged into a buffer suited to LNP formation and storage.

This is the 'bridge' from purification to formulation. If buffer and concentration are not aligned, the later LNP formation is not stable, so it is a key point that affects both yield and stability.

Salts, small molecules and ethanol are removed from the purified mRNA, and it is adjusted to the target concentration and composition. This finishing step replaces the buffer with one suitable for LNP formation and storage, and affects yield and stability.

Alternatives in practice

• Single-pass TFF (SPTFF) · Repligen KrosFlo SPTFF/Pall Cadence Inline Concentrator — High-fold concentration without recirculation, with reduced shear and shorter residence time.
• Size exclusion/desalting chromatography · Cytiva ÄKTA pure+HiPrep 26/10 Desalting/HiTrap Desalting — Buffer exchange at small to medium scale. Dilution is involved, so concentration is needed afterward.
• Dialysis · Thermo Slide-A-Lyzer G2/Spectrum Spectra/Por dialysis membranes — Lab scale only. Time-consuming and cannot be scaled up.

The preparation of two phases immediately before making LNP (lipid nanoparticles). On one side, the 'aqueous phase' in which the drug substance mRNA is dissolved in low-pH (pH4–5) acetate/citrate buffer is prepared.

On the other side, the 'organic phase' is made by dissolving the 4 components, ionizable lipid, cholesterol, DSPC and PEG lipid, in ethanol at a defined ratio. Both are prepared separately.

Particle formation occurs by instantaneously mixing the two phases, so strictly matching the N/P ratio and lipid molar ratio and pre-filtering before mixing is the starting point of quality.

LNP formation is carried out by instantaneously mixing mRNA in a low-pH aqueous phase and 4-component lipids in ethanol at a fixed N/P ratio and flow rate ratio, so it is essential to strictly prepare and pre-filter both phases for concentration, pH and lipid molar ratio (e.g., ionizable lipid:DSPC:Chol:PEG = 50:10:38.5:1.5, N/P ≈ 6) immediately before mixing.

Alternatives in practice

• Aqueous phase preparation in a citrate buffer system · The preparation system above + 50 mM sodium citrate pH4.0 — An alternative to the acetate system. Chosen by optimizing buffering capacity and encapsulation efficiency.
• Premix the lipids and supply them as a single lipid phase · Stainless steel preparation vessel + stirring + 0.2 µm PTFE/PES filter — The 4 lipids are dissolved in ethanol and premixed. Ensures consistency of the mixing ratio.

An encapsulation step that wraps mRNA, which hardly enters cells and is fragile when naked, in particles made of 4 lipids. It can be called the core unique to LNP manufacturing.

When the aqueous-phase mRNA and the ethanol-phase lipids are mixed rapidly by microfluidics or turbulence, the lipids gather spontaneously to form particles and trap the mRNA inside.

Conditions such as mixing flow rate and ratio determine particle size, uniformity and encapsulation efficiency. How well this is engineered greatly affects the delivery performance of the product, and it is the decisive point.

mRNA in its naked form hardly enters cells and is easily broken, so it is wrapped in particles made of 4 lipids. When the mRNA in the aqueous phase and the lipids in the ethanol phase are mixed rapidly, the particles self-assemble and trap the mRNA inside. It is the core step unique to this product, where the way of mixing determines particle size, uniformity and encapsulation efficiency.

Alternatives in practice

• T/impinging jet mixer (turbulent mixing) · Knauer Impingement Jets Mixer (IJM NanoScaler)/in-house stainless steel T mixer + HPLC pump — Advantageous for high flow rates and large scale. The equipment is simpler than microfluidics.
• Preformed vesicle (PFV) method · Lipid thin film hydration + extruder (Avanti Mini-Extruder/LIPEX), followed by mRNA mixing — mRNA is taken up into preformed liposomes. High degree of freedom in process control.
• High-pressure microfluidization · Microfluidics LM20/M-110P Microfluidizer — High shear gives uniform fine particles. Suited to mass production, but the equipment burden is high.

Immediately after mixing, LNP is a thin suspension containing about 7% ethanol and low pH, and cannot yet be used as is. First it is diluted and neutralized with buffer to settle the particles.

The following TFF (ultrafiltration/diafiltration) removes the ethanol and concentrates to the target concentration (1–3 mg/mL) while exchanging into a final formulation buffer at physiological pH containing cryoprotectant.

In other words, this step 'shapes freshly made particles into the form of a formulation that can be injected.' It is a real formulation step that must be passed before proceeding to sterile filtration and filling.

Immediately after mixing, LNP is a dilute suspension of about 7% ethanol at low pH (mRNA about 0.03 mg/mL) and cannot be formulated and filled as is. Removing ethanol by TFF (UF/DF), exchanging into the final formulation buffer (physiological pH, containing cryoprotectant) and concentrating to the target concentration is a mandatory standard step before sterile filtration and filling.

Alternatives in practice

• Ethanol removal, diafiltration and concentration by hollow fiber TFF · Cytiva ÄKTA flux+UFP-100-E-55 hollow fiber/Repligen KrosFlo mPES 100 kDa — Gentle shear on the LNP. Flux may be somewhat lower than with flat sheet.
• Immediate dilution/neutralization into a high-pH buffer + dialysis (small scale) · Neutralization buffer tank + Thermo Slide-A-Lyzer dialysis — For early development/small-volume studies. Cannot be scaled up.

A finishing step that decides the final form of the product. The finished LNP dispersion is sterilized with a 0.2 µm filter and aseptically filled into vials.

LNP is fragile to freezing and drying. So conditions for frozen storage and lyophilization are optimized, so that particle size and encapsulation are preserved even after thawing and reconstitution.

Only when these 2, 'how to keep sterility' and 'how to bring it to a storage form without breaking it,' are both achieved does it become a product that reaches patients. It is the final gate of manufacturing.

The finished LNP dispersion is sterilized with a 0.2 µm filter and aseptically filled into vials. LNP is easily damaged by freezing and drying, so freezing or lyophilization conditions are optimized so that particles and encapsulation are preserved even after thawing.

Alternatives in practice

• Liquid supply by frozen (−20 to −70 °C) storage · Ultra-low temperature freezers (Thermo TSX/Eppendorf CryoCube) + single-use bio-containers (Sartorius/Thermo) — Avoids lyophilization. Presupposes cold-chain logistics (COVID mRNA vaccine type).
• Spray drying/thin-film drying · Büchi Mini Spray Dryer B-290/GEA spray dryers — Aims for room-temperature stabilization. Evaluation of the effect on LNP properties is essential.
• Aseptic processing manufacture for large-particle-size systems that are difficult to filter · Class A isolator/RABS (Getinge/SKAN) + aseptic preparation — The last resort for systems that cannot be 0.2 µm filtered. Validation burden is heavy.

A quality test that measures 'how much of the mRNA remains full-length (% full-length).' mRNA is a long molecule and tends to break during manufacturing and storage.

Fragments broken partway are not translated, and efficacy drops. Making the degree of breakage visible is therefore indispensable to assuring potency.

Capillary gel electrophoresis analyzes the full-length percentage and the smear (the spread of degraded fragments). It is not a manufacturing step itself, but a step that provides the yardstick for judging quality.

mRNA is a long molecule and is easily broken during manufacturing and storage. Fragments broken partway are not translated and efficacy drops, so 'how much remains full-length (% full-length)' is measured as a quality indicator.

Alternatives in practice

• Integrity profiling by IP-RP-HPLC/UV · Thermo Vanquish/Agilent 1290 Bio LC+DNAPac RP, TEA/HFIP — High-resolution separation of full-length and degraded fragments. Sequence confirmation is also possible with MS coupling.
• Denaturing agarose/glyoxal gel electrophoresis · Bio-Rad Sub-Cell GT+ChemiDoc, NorthernMax-Gly (Thermo) reagents — Low-cost orthogonal method. Throughput and quantitation are low.
• Automated scoring such as RIN · Agilent 2100 Bioanalyzer (automatic RIN/RINe calculation) — Reports integrity as a single index. Detailed smear needs separate analysis.

An identity test that confirms the mRNA made is 'the intended molecule' and that 'there is no error in the sequence.' It is a check to prevent mix-ups and mutations.

In particular, whether the sequence of the protein produced by translation is correct is directly tied to safety and efficacy. A one-letter difference can change the effect.

After reverse transcription, the sequence is read by next-generation sequencing or RT-PCR to verify that it is as designed. It is an analytical step that assures not manufacturing but 'whether the contents are the real thing.'

Confirms that it is 'the intended mRNA' and that 'there is no error in the sequence.' It is a check to prevent mix-ups and mutations, and in particular whether the sequence of the translated protein is correct is directly tied to safety and efficacy.

Alternatives in practice

• Oligo mapping/sequence confirmation by LC-MS · Thermo Vanquish+Orbitrap Exploris 240/Waters BioAccord+DNAPac RP — Directly confirms sequence and modifications from the mass of RNase-digested fragments. Independent of NGS.
• Identity confirmation by RT-qPCR · QuantStudio 5 + sequence-specific TaqMan probes — A rapid, low-cost ID test. Cannot judge the full-length sequence.
• Restriction/probe hybridization · Hybridization system (Bio-Rad blotting) + sequence-specific probes — An orthogonal method to confirm the presence of the target sequence.

A test that measures whether the poly(A) tail at the end (3' end) of mRNA falls within the designed length. Tail length is a hidden determinant of quality.

The length of the poly(A) tail affects the stability and translation efficiency of mRNA. Efficacy drops whether it is too short or the lengths are scattered.

The mRNA is cut out with an enzyme, and the tail length distribution is analyzed by IP-RP-HPLC or LC-MS. An analytical step that confirms 'whether the lengths are aligned as targeted.'

The length of the 3' poly(A) tail affects the stability and translation efficiency of mRNA. Efficacy drops whether it is too short or too heterogeneous, so confirm that the length distribution is as intended.

Alternatives in practice

• Simultaneous cap + poly(A) analysis by the DNAzyme method · The LC-MS above (Waters BioAccord) + site-specific DNAzyme — Evaluates the 5' cap and the poly(A) tail together. Makes sample preparation more efficient.
• High-resolution capillary electrophoresis · SCIEX PA800 Plus/Agilent Fragment Analyzer (CGE) — Evaluates the poly(A) length distribution by size separation. No MS needed.
• Oligo-dT excision + gel analysis · After RNase H + oligo-dT guide digestion, Agilent Bioanalyzer/TapeStation — Simple tail length screening. Resolution is inferior to LC-MS.

A test that measures the 'size, uniformity (PDI) and surface charge (zeta potential)' of LNP particles. These 3 are the basic indicators reflecting how the particles behave in the body.

Particle size, uniformity and charge affect distribution in the body, uptake and stability. If particles are too large, heterogeneous or have unsuitable charge, delivery efficiency and safety are affected.

Particle size and PDI are measured by dynamic light scattering and zeta potential by electrophoretic light scattering at every release. An analytical step that assures particle quality numerically.

Particle size, uniformity (PDI) and surface charge affect distribution in the body, uptake and stability. Particles that are too large, heterogeneous or have unsuitable charge affect delivery efficiency and safety, so they are measured for every release.

Alternatives in practice

• Nanoparticle tracking analysis (NTA) · Malvern Panalytical NanoSight Pro/NS300 — Visualizes particle size and concentration particle by particle. Advantageous for low-concentration, polydisperse samples.
• Cryo-electron microscopy (cryo-TEM) · Thermo Glacios/Talos Arctica+Vitrobot — Direct observation of internal structure and morphology. For confirming the encapsulation state. Low throughput.
• SEC-MALS/FFF-MALS · Waters/Wyatt DAWN MALS + ÄKTA/HPLC SEC, or Postnova AF2000 FFF — Obtains absolute molecular weight and size distribution after separation. Strong for evaluating aggregates.

A test that simultaneously measures the amount of mRNA in 1 vial (content) and what percent of it is protected inside the particles (encapsulation efficiency/EE%).

Unencapsulated naked mRNA is fragile and stimulates the immune system. So it is important that both the 'amount' and the 'protected fraction' are within specification.

A fluorescent reagent called RiboGreen is used, and both values are obtained from the fluorescence difference with and without detergent. An analytical step directly tied to delivery and safety.

Measure how much mRNA is in 1 vial (content) and what percent of it is protected inside the particles (encapsulation efficiency). Naked, unencapsulated mRNA is fragile and stimulates the immune system, so it is important that both are within specification.

Alternatives in practice

• CGE-LIF (capillary gel electrophoresis with laser-induced fluorescence detection) · SCIEX PA800 Plus+LIF detection/Agilent Fragment Analyzer — Evaluates the size and amount of encapsulated mRNA at the same time. Integrity information is also obtained.
• Free/total RNA quantitation using UV (A260) · Thermo NanoDrop One/plate UV (SpectraMax) — Calculates encapsulation efficiency from the A260 difference with and without detergent. No dye needed; simple.
• RiboGreen improved method using sustainable surfactants · The fluorescence reader above + alternative solubilizer (e.g., deoxycholic acid type) — Replaces Triton X-100 (subject to REACH regulation). Improves the robustness of encapsulation efficiency measurement.

A test that confirms the 4 lipids composing the particle are present in the designed ratio. It also checks whether degradation products have increased during storage.

The quality of the ionizable lipid in particular is directly tied to delivery efficiency and safety of the mRNA. If hydrolysis products and oxidized forms increase, efficacy drops and the risk of adverse reactions rises.

Each lipid is quantified by HPLC-CAD or LC-MS and an impurity profile is drawn. An analytical step that assures the contents of the formulation at the component level.

Confirm that the 4 lipids are present in the designed ratio and that degradation products (hydrolysis products and oxidized forms) have not increased during storage. The quality of the ionizable lipid is directly tied to the delivery efficiency and safety of the mRNA.

Alternatives in practice

• RP-HPLC-ELSD (evaporative light scattering detection) · Agilent 1260 Infinity II+ELSD/Sedere SEDEX — General-purpose detection when CAD is not available. Linearity and sensitivity are somewhat inferior to CAD.
• Thin-layer chromatography (TLC) · Merck TLC Silica gel 60 plates + densitometer (CAMAG) — Simple, low-cost lipid screening. Limited quantitative accuracy.
• Nuclear magnetic resonance (NMR) · Bruker Avance NEO 400/500 MHz — An orthogonal method for lipid structure identification and ratio confirmation. Not good at detecting trace impurities.

A potency test that puts the product into cells and confirms whether the target protein can be produced properly. It is the indicator reflecting the 'real efficacy' of the product.

Even when the full-length percentage and encapsulation efficiency are in order, in the end expression in cells is the proof of effect. Only here can whether the product functions be confirmed directly.

A cell-based in vitro expression assay measures expression to assure that potency is constant between lots. An analytical step that supports release decisions.

Ultimately, confirm 'whether, when put into cells, the target protein can be produced properly.' This is the indicator of the real efficacy of the product. Dosed to cells, expression is measured to assure that potency is constant between lots.

Alternatives in practice

• Reporter (luciferase/eGFP) expression assay · Promega GloMax+ONE-Glo/Bright-Glo, or eGFP by flow cytometry (CytoFLEX) — Evaluates expression with high sensitivity and quantitatively. Requires reporter-construct mRNA.
• Evaluation of cellular uptake/expression by qRT-PCR · QuantStudio 5+TaqMan — Measures uptake before translation/transcript amount. A different indicator from protein expression.
• Confirmation of expressed protein by Western blot · Bio-Rad Trans-Blot Turbo+ChemiDoc MP — An orthogonal method to confirm the molecular weight and identity of the expressed protein. Semi-quantitative.

A general test that checks the basic safety items of an injectable together. Confirmation of sterility and endotoxin is added to pH, osmolality and appearance (foreign matter and aggregation).

That the product is sterile and that endotoxin, a pyrogen, is at or below the specification are conditions that absolutely cannot be omitted for administration to patients.

Tested by pharmacopoeia-compliant methods (sterility test, LAL test, etc.) and judged on whether the release specifications are met. An analytical step that ultimately protects patient safety.

Confirm the basic safety items for an injectable. In addition to pH, osmolality and appearance (foreign matter, aggregation), sterility and endotoxin (pyrogen) at or below the specification are mandatory release specifications for administration to patients.

Alternatives in practice

• Endotoxin quantitation by recombinant Factor C (rFC) method · Lonza PyroGene rFC Assay + fluorescence reader (BMG/SpectraMax)/bioMérieux ENDONEXT — A sustainable method that does not use horseshoe crab-derived LAL. Listing in the Ph.Eur. and others is progressing.
• Rapid sterility test (nucleic acid amplification/respiration-metabolism method) · bioMérieux BACT/ALERT/Rapid Micro Biosystems Growth Direct — Results in a short turnaround. Presupposes validation against the culture method.
• Subvisible particle test (light obscuration/flow imaging) · Beckman Coulter HIAC 9703+/Yokogawa FlowCam 8000 — Particle test such as USP<788>. Also applied to evaluating LNP aggregates.