In the field of In Vitro Diagnostics (IVD), numerous biochemical, immunological, and chemiluminescence assays rely on a class of “unsung heroes” — redox coenzymes. Acting as “electron transporters” in enzymatic reactions, they precisely transfer electrons and hydrogen atoms within reaction systems, enabling stable generation and capture of detection signals.

As a provider of IVD raw material and reagent solutions, we have compiled the definitions, storage, transportation, opening and sampling procedures, shelf-life management, and typical applications of NAD, NADH, NADP, and NADPH. This guide aims to help customers enhance reagent stability, reduce losses, and ensure the reliability of test data.

1. Getting to Know Them: Definitions and Nature

Commonalities: All are nicotinamide nucleotide coenzymes that can reversibly transfer electrons/hydrogen in enzymatic reactions, making them essential raw materials for various IVD testing platforms.

• NAD⁺: A key coenzyme involved in cellular energy metabolism
• NADP⁺: A coenzyme involved in biosynthetic reactions
• NADH: An important electron carrier in the cellular respiratory chain
• NADPH: A crucial coenzyme providing reducing power

1. Storage: Low Temperature · Light Protection

III. Opening and Sampling

Although opening and sampling lyophilized powders are routine operations, they directly affect the purity, activity, and stability of raw materials. The key principles are low temperature, dryness, light protection, speed, airtightness, as well as complete documentation and shelf-life tracking. Strict adherence to this SOP can effectively reduce quality risks in reagent production and ensure the reliability of test results.

3.1 Pre-Opening Inspection

• Verify Information: Ensure the batch number, expiration date, storage conditions, and Certificate of Analysis (COA) are consistent.
• Visual Inspection: Check for no cracks, leaks, or damage to the bottle seal.
• Environment Preparation: Pre-cool the operating area in advance (cold room or ice bath) and sterilize/pre-cool tools.

3.2 Opening Operation

• Alcohol Disinfection: Wipe the outer surface of the bottle and cap with 75% ethanol and allow to air dry.
• Burn the Neck (Glass Ampoules): Gently heat the neck of the ampoule with an alcohol lamp or Bunsen burner until red-hot, then quickly break it off using sterile gauze (to avoid glass shards falling into the powder).
• For Screw-Cap Bottles: First, slowly loosen the cap to release a small amount of air from the top (reducing moisture absorption due to negative pressure), then fully open the cap.
• Moisture Prevention: Open the bottle quickly and minimize the time the bottle mouth is exposed (≤10–15 seconds).

3.3 Sampling

• Sampling Tools: Use sterile, dry forceps or spatulas; avoid direct contact with hands.
• Tap the Bottle Wall: Loosen the lyophilized powder to ensure uniformity and prevent uneven sampling due to caking.
• Quantitative Weighing: Weigh the required amount as needed (preferably using an analytical balance in a cold room or laminar flow hood) to avoid repeated sampling.
• Avoid Pouring Back: Do not pour sampled material back into the original bottle to prevent contamination of the entire batch.

3.4 Sealing and Storage

• Immediate Sealing: After sampling, quickly tighten the cap or seal with a new heat-sealing film (for ampoules, use a sterile rubber stopper + aluminum cap for sealing).
• Nitrogen Purging (Optional): For oxidation-sensitive lyophilized powders (e.g., NADH, NADPH), purge with high-purity nitrogen before sealing to reduce residual oxygen.
• Labeling: Attach a new label to the bottle indicating the batch number, opening date, remaining quantity, and sampler.
• Storage: Return to the dedicated refrigerator under the original storage conditions (-20℃ or -80℃), and avoid mixing with other chemicals.

3.5 Precautions

• Moisture Prevention: Lyophilized powders are highly hygroscopic. Once damp, they tend to cake and degrade. The relative humidity of the operating environment should be ≤40% RH.
• Light Protection: Photosensitive coenzymes (NADH, NADPH) should be handled under red or yellow light, and the bottle body should be wrapped in aluminum foil if possible.
• Oxidation Prevention: Minimize exposure of reduced coenzymes to air before and after opening; use vacuum or nitrogen-filled packaging if necessary.
• Avoid Repeated Opening: It is recommended to aliquot into small bottles for single use to reduce activity loss caused by multiple openings of the entire bottle.
• Shelf-Life Management: The shelf life of opened products under original storage conditions should be evaluated based on stability data. Generally, solids can be used within the original expiration date, but regular inspection of appearance and activity is required.

3.6 Common Problems and Corrective Measures

IV. Typical Application Projects

① Biochemical Testing

• Blood Glucose, Lactic Acid (GOD/LDH + NAD⁺→NADH)
• ALT, AST (Transaminases + NADH Monitoring)
• Total Cholesterol, Triglycerides (Oxidase–POD System + NADH Color Development)

② Metabolism and Special Protein Testing

• Homocysteine (Enzymatic Cycling Amplification + NADPH)
• Bilirubin, Uric Acid (Dehydrogenase System)

③ High-Sensitivity Enzymatic Cycling Amplification

• Trace Ammonia (Glutamate Dehydrogenase Cycling + NADH)
• Bile Acids, Vitamin B6 (3α-HSD or Transaminase Cycling)

④ Immunological and POCT Assistance

• Fluorescent ELISA (NADPH + Specific Substrate Produces Fluorescence)
• Chemiluminescent Immunoassays (Coenzyme Regeneration Extends Luminescence Duration)
• POCT Devices such as Blood Glucose Meters (Electrochemical Method Indirectly Reflects NADH Regeneration)

Note: The optimal pH and temperature vary among different projects. Interference from reducing substances (e.g., vitamin C, glutathione) should be avoided.

NAD, NADH, NADP, and NADPH are key nodes in the IVD detection signal chain. By definition, they are nicotinamide nucleotide redox coenzymes that can reversibly transfer electrons and hydrogen in enzymatic reactions, thereby driving the generation of colorimetric, fluorescent, or chemiluminescent signals.

Scientific storage and transportation, standardized opening and usage procedures, and precise shelf-life management not only extend the lifespan of coenzymes but also ensure the accuracy and reliability of test data.

As your trusted  raw material partner, we are committed to excellence in product quality and strive to help you reduce risks and improve efficiency in production and quality control through professional technical sharing.