Gold nanoparticles so small they appear intensely red and remain suspended in water serve as the core component that enables rapid assays (point-of-care, POC, assays) to detect minute traces of important substances. To accomplish this feat, nano-gold particles (gold sol) must be coated with appropriate receptors that react specifically with the molecules to be detected. BioAssay Gold was organized for the purpose of creating the gold sols used in ultra-sensitive rapid diagnostic tests.

If you need a rapid, POC assay to a particular goal, or are experiencing challenges with the sensitivity of a current assay, please give us a call at 301.874.8888. BioAssay Gold has great solutions to offer.

BioAssay Gold product's outstanding sensitivity is a result of the synergistic action of four technologies that differentiate our products and services: 1) proprietary concentrated Naked Gold® sol 2) unique conjugation techniques 3) advantages of our patent-pending C-FLAT® assay platform and 4) optimized Tell-Tale Gold® impregnated ribbon. The Company's mission includes a service to assemble gold sols into working assay systems. See Product Details below.

Product Details:

Iso-Gold™ Rapid Mouse -Monoclonal Isotyping Kit NEW Options for Rapid Isotyping: BioAssay Gold has developed a five-minute rapid mouse-monoclonal isotyping kit with ELISA sensitivity for Mab class and subclass determination. In less than 10 minutes the isotype is determined. In comparison, it may take a day and a half to set up and run the ELISA. Save a day of labor and deliver monoclonal identity results!
	Photo on the left shows test kit examples. There are a number of ELISA-based isotyping kits on the market. These kits require the customer to supply their own plates, do the coating, incubation and kit development.  One latex-bead-based "rapid" isotyping kit is also marketed, but the sensitivity increase of a gold-sol-based assay versus a latex-based assay gives the advantage to the gold assay.
IsoGold Rapid-Mouse-Mononclonal Isotyping Kit is a rapid lateral flow assay with ELISA sensitivity for monoclonal antibody class and subclass determination. The assay can be run on both tissue culture supernatant fluid and on mouse ascites fluid. Each IsoGold test kit contains ten (10) cassette pouches  -  ten (10) cassettes for detecting IgG1, IgG2a , and IgG2b isotypes; and ten (10) cassettes for detecting IgG3, and IgM, and IgA antibodies. The kit also contains one (1) 45 ml bottle of Sample Diluent. Store kit and components at room temperature – Shelf life 18 months. Product Code Description QTY Size TISO-001 Iso-Gold Rapid Mouse-Monoclonal Isotyping kit 1 5 test pouches ISOT-001 Iso-Gold Rapid Mouse-Monoclonal Isotyping kit 1 5 test pouches Assay Utility: Determining the class and subclass of a mononclonal antibody is useful in determining the best immunoglobulin purification method.  For example, IgA and IgM are often best purified by size (gel exclusion) or on immuno affinity separation columns whereas IgG2a and IgG2b can be purified on protein A at a pH of 7 to 8.  IgG1 binds best to protein A at a pH of  8 to 9.  In addition, each class and isotype can be digested to Fab fragments using the appropriate amount of pepsin or other enzymes for each isotype or antibody class. Assay background information:There are two (2) cassettes in each of the ten (ten) pouches: one cassette for detecting IgG1, IgG2a, and IgG2b; the other cassette detects IgG3; IgA, and IgM. When a properly diluted sample containing a specific isotype is added to the sample-well, specific-class and subclass soluble complexes are formed with the embedded gold conjugates. These complexes travel the length of the membrane and are resolved on the anti-isotype and class-specific antibody-impregnated membrane. Typically, when antibodies are tested at 10 nanograms per milliliter, results are read at five (5) to ten (10) minutes. (Results should not be read after ten (10) minutes.) See BioAssay Gold' Application Notes or Technical Data for procedures for monoclonal antibody ascites fluid, for cell culture fluid, and for supernatant fluid.

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Naked Gold ® - unlabeled gold sol, 15 or 50 OD (Optical Density). Gold sols for ligand conjugation, optimized for rapid assay development and POC rapid diagnostic products. Naked gold is produced by a proprietary process that does not involve the traditional boiling and centrifugation methods. This unique process allows the end-user to directly coat antibody or soluble proteins onto gold without the need to concentrate the gold via centrifugation. By eliminating the gold concentration centrifugation step, the potential for aggregates is greatly minimized. Our high quality gold sol is consistently reproducible.

Dressed Gold ® -  (Labeled Colloidal Gold Sol, nanoparticles) conjugated gold sol, either custom or a stock gold conjugate. Gold sols optimized for rapid assays. Inquire regarding custom conjugation of gold particles to clients' ligands. BioAssay Gold' Dressed Gold is produced from our proprietary Naked Gold sol and has not been boiled or centrifuged. The highly active gold particles greatly increase the sensitivity in lateral flow tests. Dressed Gold is available in 40 nm size at 15 OD. (Custom conjugations may be requested in 40 nm size at 50 OD.)

Dressed Gold®, 40 nm - 15 OD

Product Code	Description	QTY	Size	OD
DGHG – A001ml	Goat anti-human IgG (H & L)	1 ml	40 nm	15
DGHG – A009ml	Goat anti-human IgG (H & L)	9 ml	40 nm	15
DGHA – A001ml	Goat anti-human IgA (Alpha  Chain)	1 ml	40 nm	15
DGHA – A009ml	Goat anti-human IgA (Alpha  Chain)	9 ml	40 nm	15
DGHM – A001ml	Goat anti-human IgM (Mu Chain)	1 ml	40 nm	15
DGHM – A009ml	Goat anti-human IgM (Mu Chain)	9 ml	40 nm	15
DGMG – A001ml	Goat anti-mouse IgG (H & L)	1 ml	40 nm	15
DGMG – A009ml	Goat anti-mouse IgG (H & L)	9 ml	40 nm	15
DGRG – A001ml	Goat anti-rabbit IgG (H & L)	1 ml	40 nm	15
DGRG – A009ml	Goat anti-rabbit IgG (H & L)	9 ml	40 nm	15
DRGG – A001ml	Rabbit anti-goat IgG (H & L)	1 ml	40 nm	15
DRGG – A009 ml	Rabbit anti-goat IgG (H & L)	9 ml	40 nm	15
DPRA – A001 ml	Protein A	1 ml	40 nm	15
DPRA – A009 ml	Protein A	9 ml	40 nm	15
DPRG – A001 ml	Protein G	1 ml	40 nm	15
DPRG – A009 ml	Protein G	9 ml	40 nm	15
DSTA – A001 ml	Streptavidin	1 ml	40 nm	15
DSTA– A009 ml	Streptavidin	9 ml	40 nm	15

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Tell-Tale Gold ® - gold sol impregnated ribbon. BioAssay Gold' Tell-Tale Gold polyester ribbon impregnated with our conjugated Protein A and Protein G concentrated gold particles is dried in a special way that ensures rapid release. We also offer gold ribbon for any monoclonal/ polyclonal antibody or soluble protein on a custom basis.

Gold in a Box™ Kit, for preparing highly reactive antibody and purified soluble protein gold conjugates - Lateral flow chromatographic and flow-through tests offer fast detection of critical components for use in point-of-care testing. The key to these tests is the ability to covalently attach antibodies to intensely colored, nanometer particles. Gold sols that bind ligands through a sulfur bond have proved highly successful for this application. For optimal binding of the antibody or protein while retaining a high degree of specific activity, the pH of the gold sol must be adjusted to slightly above the iso-electric point of the coating antibody or protein. This is done through a series of pH titrations with the provided buffers. Varying amounts of buffers A and B, and varying amounts of buffers C and D are added to the gold to create a pH 5-11 range. Next, antibody or protein is added and after 30 minutes the reaction is stopped. This convenient “Gold in a Box” kit allows you to quickly (in less than 50 minutes) determine the pI, and optimal coating range for your antibody or soluble protein.

Kit Components for NGIB01-A018 (components for A044 size and A100 size are proportionally larger):

• Naked Gold Sol 40 nm - 9.0 ml (cap with black ring)
• Naked Gold Sol 20 nm - 9.0 ml (cap with red ring)
• Buffer Solution A - 1.0 ml (cap with black dot)
• Buffer Solution B - 1.0 ml (cap with green dot)
• Buffer Solution C - 1.0 ml (cap with blue dot)
• Buffer Solution D - 1.0 ml (cap with red dot)
• BSA Blocking Stabilizer Solution - 2.0 ml (clear cap)
• Gold Drying Buffer – 2 ml (cap with purple dot)
• Treated polyester Ribbon 4 strips - 30 cm in length
• 1 ml pipette

Materials required but not provided:

• Clean glass or polystyrene test tubes (12 x 75 mm)
• Pipettes and tips

Sample Preparation:
The antibodies or proteins used with this kit must be at a concentration of 1 mg/ml or greater and should be in a 0.5 X PBS buffer solution. If they are not in a 0.5 X PBS buffer solution, then dialyze the antibody or protein against 0.5 X PBS. Proteins at a concentration of 2 mg/ml or greater should be in 1 X PBS.

Generic Procedure, Gold in a Box:
Note: Use aseptic technique when handling the gold sol.
1. Shake or swirl gold to resuspend any settled gold. Place 0.5 ml Naked Gold sol into ten (10) clean individual test tubes.
2. Label each tube with the pH value (or, 1 through 10) from the provided pH charts.
3. Use the pH charts to add varying amounts of buffer in microliters to each test tube. Shake to mix.
4. Add antibody solution (See Sample Preparation Section) and mix rapidly. For the 40 nm gold, ideally, 7 µl of a 2 mg/ml solution of antibody or protein is optimal. For the 20 nm gold, ideally, 16 ul of a 2 mg/ml solution of antibody or protein is optimal.
Note: The saturation point for 40 nm gold is typically near 30 mcg of antibody per ml of gold. The saturation point for 20 nm gold is about 70 to 75 mcg of antibody per ml of gold.
5. A deepening purple color and/or black precipitate on some tubes indicates that the antibody or protein is below its iso-electric point, leading to cross-linking of individual gold sols. Cross-linked sols cannot be used in immunological assays and should be discarded. Deep purple sols are usually mostly inactive as well. Only tubes with a slight purple color or no change in color are useful for immunological assays.
6. Allow the reaction to continue for a total of 30 minutes.
Note: See section below on “Stability of Gold Conjugates”.
7. Stop the reaction by the addition of 50 µl of Blocking Stabilizer Solution.
Note: In some conjugates that result in non-specific reactivity, it is often best to allow the blocker to react for an additional 16 hours at room temperature.

Stability of Gold Conjugates, Gold in a Box:

• Gold particles completely coated with protein take on the properties of the coating proteins and become very stable in solutions of high ionic strength. An excellent way to test the effectiveness of the conjugation reaction is to combine 10 µl of coated gold sol (prior to the addition of the BSA blocking solution) with 10 µl of 1 M NaCl. Sols with incomplete coating will fall out of solution (turn black), while completely coated sols will remain stable (red).
• Conjugate is now ready for use in a rapid assay at nominal usage of 5-15 µl per assay. Tubes that have a slight color change and ones with no color change should be assayed for optimal activity. Tubes with the best activity are usually a good indicator of the approximate iso-electric point of the coated antibody or protein.
• In order to effectively dry down the gold, add 0.1 ml of Gold Drying Buffer for every 1.0 ml of conjugate. Mix thoroughly. Apply gradually and evenly to the treated polyester ribbon with the provided 1 ml pipette.
• Place ribbon in a vented 37° C oven or incubator for four (4) hours to dry thoroughly.
• If a vented incubator is not available, use a hairdryer set to deliver 37° C heat at a ten (10) inch distance from the ribbon surface. Usually, three (3) or four (4) minutes in a wave-motion will suffice to thoroughly dry the ribbon.
• Store all dried ribbons in a glass tightly sealable container containing ample desiccants (granular or pouch-form).
• This generic procedure may be modified or scaled as needed. When developing a new assay, it is important to determine the optimal amount of ligand to add to the gold particles. Once the tubes have been assayed, it is useful to further optimize binding by both decreasing or increasing the amount of antibody added to each tube. Often, a 20% increase or decrease in antibody or protein added is sufficient to yield an optimal coating procedure. A few cases require a 40% or more increase or decrease in coating antibody or protein.

Discussion, Gold in a Box:
A sensitive lateral flow assay requires that all of the antibody or protein that is added to the gold sol be irreversibly bound to the beads. Any free antibody or protein serves to short-circuit the assay. This behavior ultimately sets the sensitivity limits of an assay.

Nano-gold particles remain in solution because they repel each other due to a significant negative charge. This means that proteins bind to gold particles through both ion-exchange attraction and covalent bonding of protein thiols (-SH) with surface gold. The challenge for preparing stable gold conjugates in this “Gold in a Box” format depends upon one's ability to manage the binding of antibody or proteins at or near their iso-electric point. In a few cases, the titration of the pH may need to be fine tuned.

The antibodies or proteins in the sample must display a suitable number of surface thiols (-SH). Proteins with no surface thiol groups bind exchangeably with gold particles through ion-exchange interactions. Such proteins do not form stable gold sols that are suitable for flowing chromatographic assays. Equally problematic are protein preparations where surface thiols have been capped or protected by reaction with N-ethyl maleimide or iodoacetic acid.

Application of Gold conjugates, Gold in a Box:
Stabilized gold conjugates made from concentrated sols are ready for use in lateral flow and flow-through assays without additional optimizations. Typically, 5-15 µl gold conjugate per test will give optimally sensitive assays. The gold conjugate is excellent for use in a variety of gold amplified assay procedures. This includes BioAssay Gold' patent-pending, ultra-sensitive C-FLAT technology. Researchers interested in evaluating this technology may contact BioAssay Gold for a research use license with no fee.

Assay Development - BioAssay Gold develops and/or manufactures the rapid diagnostic product(s) requested by customers. BioAssay Gold personnel are gold nanoparticle specialists.

CTU (TM) Central Testing Units - BioAssay Gold designs and manufactures rapid assay components as "gold in progress" for final assembly by and for the specific requesting client. A subset of Assay Development includes "CTUs" that are to rapid tests what the central processing unit is to computers. CTUs empower small, local enterprises to customize lateral-flow tests to local needs. The product recognizes and builds upon local knowledge and experience by making partners of regional experts.

C-FLAT® Counter-Flow Lateral Amplified Test - BioAssay Gold' novel, patent-pending lateral flow immunodiagnostic device that incorporates unique gold sol production, conjugation expertise, and impreganted ribbon technology into the counter-flow lateral platform.

BioAssay Gold creates gold sols and gold-sol-based assays with superior performance and reliability, in combination with reduced manufacturing costs.

Features and Advantages of BioAssay Gold Products:

• A 10- to 15-fold increase in gold nanoparticle concentration over existing technology. 10 to 15 OD (Optical Density) gold nanoparticle sols, versus 1 OD produced by the current technology protocols.
• Ready-to-use gold particle sols (no concentration required)
• Laboratory time and labor saved: Unlike current technology, no centrifuging is required
• Increased consistency in product quality: Reproducibility of conjugation is improved with BioAssay Gold' new technology
• Reduced manufacturing waste by 10% to 20%, and increased manufacturing efficiency
• Uniform monomer particles: No aggregates, and dramatic reduction of particle waste

BioAssay Gold gold sol products solve a problem of gold particle concentration that exists with current technology and all competitive products. Benefits to the customer include:

• Customers who manufacture their own diagnostic products will find that the 10 to 15 OD formulation significantly improves their process and reproducibility, while reducing costs. Improved rapid assays.
• Improved reproducibility of all rapid diagnostic products
• Reduced waste of gold particles and precious antibodies and antigens
• Reduced laboratory and production costs, leading to increased profits

Comparison of BioAssay Gold Products to Current Technology
This image immediately conveys the difference between 10X gold concentrate possible with advanced BioAssay Gold technology, and 1X gold concentration from current technology. 

The dark red BioAssay “Cabernet Sauvignon” is BioAssay Gold' red gold sol. The light rose solution is a gold sol created using current technology. BioAssay Gold' personnel created the gold sols in the vials to visually demonstrate the difference between 1 X gold and 10 X gold optical densities. The vials contain gold from the same reaction.