Title: Gene Gun Microparticles: Which Metal Is Used for DNA Delivery?

The correct answer is: Gold. Microparticles used in the gene gun (biolistic) method for DNA delivery are most commonly made of gold, which is coated with DNA and shot into target cells.

Correct Answer: Gold

Gold microparticles are widely used in the gene gun method because they are biologically inert, non‑toxic, and chemically stable. Gold particles can be finely prepared in the required micron size range and efficiently coated with plasmid DNA without reacting with or degrading the genetic material. During biolistic transformation, these DNA-coated gold particles are accelerated (usually using compressed gas such as helium) to penetrate cell walls and membranes, allowing the DNA to enter the cell and potentially integrate into the genome.

Why Gold Is Preferred in Gene Gun Technology

• High density helps particles achieve sufficient momentum to penetrate target tissues.

• Chemical inertness minimizes unwanted reactions with DNA or cellular components.

• Low toxicity makes it suitable for both plant and animal cell transformation.

• Proven efficacy: gold or tungsten are repeatedly cited as the standard carriers in biolistic methods.

Although tungsten is also used in some systems, many exam-oriented sources specify gold as the correct choice when only one metal must be selected, as in the given MCQ.

Explanation of All Options

1. Gold (Correct)

Gold is the standard metal for microparticles in many modern gene guns. These particles are coated with DNA or RNA and then fired into target cells to achieve transformation or transfection. Its inertness, non‑toxicity, and good DNA-binding characteristics make it ideal for this physical gene delivery method.

2. Silver (Incorrect)

Silver is not typically used for gene gun microparticles. While silver nanoparticles are well known for their antimicrobial properties and are used in coatings, dressings, and some biomedical applications, their potential cytotoxicity and different surface chemistry make them less suitable as standard carriers for DNA in biolistic systems.

3. Copper (Incorrect)

Copper is a reactive metal that can participate in redox reactions and catalyze the formation of reactive oxygen species. Such reactivity can damage nucleic acids and cellular structures, which is undesirable in a precise gene delivery method. For this reason, copper is not used for microparticle preparation in gene gun technology.

4. Titanium (Incorrect)

Titanium is valued in medicine for implants because it is strong, lightweight, and biocompatible, especially in bulk form. However, it is not standard for the fine, dense microparticles needed for efficient DNA bombardment in a gene gun, and it does not offer clear advantages over gold or tungsten as a gene carrier.​