Gold Nanoparticle Storage and Handling

1. Storage

a. Temperature and Humidity Control  

- Temperature:  

Conventional gold nanoparticle solutions (such as citrate-stabilized GNPs) should be stored at 4¡ãC in the dark, with air isolation and no freezing (freezing may cause ice crystals to damage the particle surface stabilizing layer, leading to aggregation).  

- Humidity:  

The storage environment must be dry to prevent condensation on the inner wall of the container from affecting the solution concentration or causing mildew (especially for systems containing biomolecules).  

b. pH and Ionic Strength Control  

- pH Value:  

Most gold nanoparticles are stable within the pH range of 6¨C9. Avoid strongly acidic (pH < 3) or strongly alkaline (pH > 11) environments, as these may cause dissociation of surface modifiers or oxidation of the gold surface.  

- Ionic Strength:  

High-concentration electrolytes (e.g., NaCl > 10 mM) should be avoided in the storage medium to prevent shielding of particle surface charges and induce aggregation.  

c. Selection of Storage Containers  

- Material Requirements:  

Glass containers (such as glass bottles and centrifuge tubes) are preferred to avoid contamination of particles by plasticizers released from plastic containers (e.g., PVC) or metal ions (e.g., trace metals in PET).  

If plastic containers are used, inert materials (such as polypropylene PP) should be selected and pre-soaked in ultrapure water overnight to remove surface impurities.  

- Sealing and Anti-Volatility:  

Containers must be equipped with airtight lids to prevent solution volatilization, which may lead to increased concentration or particle deposition.

2. Shelf Life

3. Handling

a. Ultrasonic Treatment:

For some of our products, gold nanoparticles may be deposited at the bottom of the flask due to long-term storage. This can occur because gold nanoparticles in the solution naturally precipitate at the flask bottom due to size or chemically induced attraction, or agglomerate due to ionic, magnetic, or chemically induced attraction, especially for larger particle sizes. Unlike aggregation, these are natural phenomena that can be reversed through ultrasonic treatment. Depending on parameters such as size, charge, and others, the precipitated particles should be resuspended by vortexing until a uniform solution is obtained. To minimize these reversible situations, please ensure that you store and handle your products as recommended in the storage and handling instructions. We typically use an ultrasonic cleaner for 15 seconds to 1 minute. We ensure that the water level is at a point where visible ultrasonic ripples can be seen in the water. Alternate ultrasonic treatment with shaking/mixing the microcentrifuge tube to resuspend the gold nanoparticles into the solution.  

b. Centrifugation

During experiments, it may be necessary to process the product to remove free reducing agents, stabilizers, electrolytes, etc. A simple method for processing gold nanoparticles is centrifugation, and you can refer to the table below for operation:

Optical Properties of gold nanoparticles of various sizes

4. Dilution

Gold nanoparticles have corresponding selection guidelines, and customers can view the corresponding buffer solution based on the selected microspheres according to the guidelines.

5. Product Use

For research use only. Not for any clinical, therapeutic, or diagnostic use in humans or animals.

Reference

[1] Sarah John. "Green Synthesis of Gold Nanoparticle using Nutmeg Fruit Extract." International Journal of Science and Research (IJSR) 5(2019).

[2] Jauregui-Gomez D , Bermejo-Gallardo O M , Moreno-Medrano E D ,et al.Freeze-drying storage method based on pectin for gold nanoparticles[J].Nanomaterials and Nanotechnology, 2017, 7:184798041769732.DOI:10.1177/1847980417697328.