Frequently Asked Questions
FAQ: Frequently Asked Questions About Colloidal Gold
Learn about benefits, usage, safety, nanoparticle size, concentration, and how to choose the best product for your needs.
1. What is Colloidal Gold?
Colloidal gold is a suspension of microscopic, nano-sized particles of pure 24k gold in a liquid, typically purified water. These particles are so small they remain suspended indefinitely, giving the colloid its characteristic red or reddish-purple color. It is not a chemical compound but a pure elemental mineral in a bioavailable form.
2. What are the Potential Benefits of Colloidal Gold?
Colloidal gold is primarily associated with supporting mental clarity, focus, and a sense of emotional balance. Many users report it helps promote a state of calmness and cognitive function. Historically, gold has been valued for its purported properties, and modern nanotechnology allows for enhanced bioavailability. Note: These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
3. How is GoldColloid.com's Product Different?
Important Prerequisites & Principles
Antibody Quality: This is the most critical factor. You must use a high-affinity, purified antibody (preferably IgG). Avoid antibodies with preservatives like sodium azide (NaN₃) or carriers like BSA, as they interfere with conjugation. Use low-sodium azide (<0.01%) or thimerosal if necessary.
Gold Nanoparticles: Your 40nm citrate-AuNPs should be a characteristic red color. Any graying or precipitation indicates instability. Store at 4°C and let them reach room temperature before use.
pH is King: Antibodies bind to the gold surface via electrostatic interactions between the negatively charged citrate gold and positively charged groups on the antibody (lysine residues). The pH of the gold solution must be slightly acidic to ensure the antibody is positively charged. The isoelectric point (pI) of your antibody is your guide.
Work Cleanly: Use high-purity water (e.g., Milli-Q) and clean glassware/plasticware to avoid contaminants that can cause aggregation.
Step-by-Step Protocol
Step 1: Determine the Optimal pH and Minimum Antibody Concentration (Preliminary Testing)
This step is crucial to avoid wasting precious antibodies and gold.
Prepare a 0.2 M K₂CO₃ solution (for raising pH) and a 0.1 M HCl solution (for lowering pH). Filter through a 0.22 µm membrane.
Determine your antibody's pI. If unknown, assume a pI of ~8-9 for most IgGs and start testing around pH 8.0. If the pI is known, aim for a pH 0.5 units below the pI.
Prepare a serial dilution of your antibody in a low-salt buffer (e.g., 2 mM Borax, pH 9.0). A typical range is from 2 µg/mL to 25 µg/mL.
Aliquot 100 µL of your gold nanoparticle solution into several microcentrifuge tubes.
Adjust the pH of each aliquot carefully using tiny volumes (e.g., 1-5 µL) of 0.2 M K₂CO₃ or 0.1 M HCl. Use pH strips (with a range of 3-10) for quick checks. Have tubes at different pH values (e.g., 7.0, 7.5, 8.0, 8.5, 9.0).
Add 10 µL of each antibody dilution to the pH-adjusted gold tubes. Mix gently. Include a negative control (water instead of antibody).
Incubate for 1-2 minutes at room temperature.
Add 100 µL of a 10% NaCl solution to each tube and mix.
Observe after 5-10 minutes:
Stable: The solution remains red/pink. No color change or precipitation.
Unstable: The solution turns blue/purple and precipitates (aggregation).
The minimum antibody concentration that prevents aggregation (stays red) at its optimal pH is your target. To be safe, use 120% of this minimum value for the final conjugation.
Step 2: Conjugation of Antibody to 40nm AuNPs
Scale Up: Based on your test, calculate the volume of gold solution you need. For a standard LFA pad, 1-5 mL is a good start.
Adjust pH: In a clean glass vial, adjust the pH of the entire gold solution to the predetermined optimal value using 0.2 M K₂CO₃. Add it dropwise while stirring vigorously.
Add Antibody: While stirring the gold solution, quickly add the predetermined volume of antibody (at 120% of the minimum stabilizing concentration). Continue stirring for 1-2 minutes.
Incubate: Stop stirring and let the mixture incubate at room temperature for 30-60 minutes. This allows the antibody to adsorb onto the gold surface.
Step 3: Blocking and Stabilization
After conjugation, the surface may still have bare spots. We block these to prevent non-specific binding and stabilize the conjugate for storage.
Prepare a Blocking Solution: A common and effective blocker is 1% Bovine Serum Albumin (BSA) or 1% Polyethylene Glycol (PEG) 20,000 in a weak buffer (e.g., 20 mM Borax, pH 9.0, containing 0.05% NaN₃ as preservative). Filter (0.22 µm).
Add Blocker: After the conjugation incubation, add the blocking solution to achieve a final concentration of 0.05-0.1% BSA or 0.1% PEG. Stir gently and incubate for another 15-30 minutes.
Step 4: Purification and Concentration (Removing Unbound Antibody)
Unbound antibody can compete in the LFA and reduce test sensitivity.
Centrifugation: This is the standard method.
Transfer the conjugated AuNP solution to centrifuge tubes.
Centrifuge conditions for ~40nm AuNPs: ~14,000-16,000 x g for 45-60 minutes at 4°C. Optimize this for your specific centrifuge and rotor.
You will see a tight, dark red pellet at the bottom and a clear/lightly colored supernatant.
Discard Supernatant: Carefully aspirate and discard the supernatant, which contains unbound antibody, salts, and excess blocker.
Resuspend: Resuspend the pellet in your desired storage buffer. A common buffer is 20 mM Tris-HCl, pH 8.2, containing 1% BSA, 5% sucrose, and 0.05% NaN₃.
Sucrose/Trehalose is a cryoprotectant that prevents aggregation when the conjugate is dried onto the conjugate pad.
Resuspend to a volume 1/10th of the original gold volume to create a 10x concentrated conjugate stock.
Sonication: Gently sonicate the resuspended conjugate in a water bath sonicator for ~10-20 seconds to break up any aggregates and create a homogenous solution.
Step 5: Characterization (Optional but Recommended)
UV-Vis Spectrophotometer: Scan from 400-700 nm. A good conjugate will have a peak absorbance (λmax) around ~525-528 nm. A shift to longer wavelengths (>535 nm) indicates aggregation.
Test on Strip: The best test is to run your conjugate on an LFA strip with your target analyte and control lines to check for sensitivity, specificity, and background.
Using the Conjugate in Lateral Flow
Conjugate Pad Treatment: The conjugate is typically sprayed onto a glass fiber or polyester conjugate pad.
Drying: The pad is dried overnight in a desiccator or for 1-2 hours at 37°C.
Assembly: The dried conjugate pad is assembled with the sample pad, nitrocellulose membrane (with test and control lines), and absorbent pad to create the complete lateral flow strip.
4. What Does "PPM" Mean?
PPM stands for Parts Per Million. It refers to the weight-to-weight concentration of gold particles in the suspension. For example, a 5 PPM solution contains 5 milligrams of pure gold per liter of liquid. A higher PPM means a higher concentration of gold nanoparticles.
5. Is a Higher PPM Always Better?
Not necessarily. The effectiveness is influenced by both concentration (PPM) and particle size. Smaller nanoparticles have a larger total surface area relative to their volume, which can influence their interaction with the body. We optimize our formulations for the ideal balance of particle size and concentration for maximum bioavailability.
6. What is the Particle Size of Your Colloidal Gold?
Our advanced manufacturing process produces exceptionally high quality 40 nm nanoparticles, 40 nanometers in diameter. This tiny size is for stability and potential bioavailability, as it allows the particles to remain in suspension and be more readily utilized.
7. How Do I Use Colloidal Gold?
Colloidal gold is typically taken orally. Shake the bottle gently before use. Hold the required amount under the tongue for 30-60 seconds before swallowing to allow for sublingual absorption, or add it to water or juice. Always follow the dosage instructions on the product label or as directed by your healthcare professional.
8. Is Colloidal Gold Safe?
Our colloidal gold is made from 99.999% pure 24k gold and purified water, with no additives or fillers. It is generally recognized as safe for consumption. However, if you are pregnant, nursing, taking medication, or have a known medical condition, it is always recommended to consult with a healthcare provider before use.
9. How Should I Store My Bottle?
Store your colloidal gold in its original glass bottle in a cool, dark place away from direct sunlight and strong electromagnetic fields (e.g., microwaves, refrigerators, cell phones). Do not freeze it. Proper storage ensures long-term stability and potency.
10. Why Does the Color Vary?
The color is a direct indicator of particle size and quality. A vibrant ruby red color indicates small, nano-sized spherical particles (optimal). A darker purple or grayish hue can indicate larger particles or aggregation. Our consistent process ensures a characteristic red color, confirming high quality.
11. Do You Test Your Products?
Absolutely. We rigorously test every batch using advanced methods like Transmission Electron Microscopy (TEM) to verify particle size and shape, and Atomic Absorption Spectroscopy to confirm precise PPM concentration. We guarantee the purity, concentration, and quality of our product.
12. How Long Does Shipping Take?
We process orders quickly, typically within 1-2 business days. Shipping times depend on your location and the selected method. US orders generally arrive within 3-7 business days. You will receive a tracking number as soon as your order ships.