Microprojectiles

Microprojectiles are small solid particles used as carriers to deliver genetic material or other biomolecules into cells by ballistic bombardment. In plant biology they are most commonly gold or tungsten beads coated with DNA or RNA and propelled into tissues by a gene gun. The particles, typically 0.5 to 3 micrometers in diameter, are accelerated to high velocity and penetrate cell walls and membranes, depositing their cargo inside the target cells.

The delivery mechanism relies on physical penetration rather than chemical uptake. A device releases a burst of compressed gas or uses a rupture disk to launch the coated microprojectiles toward the sample. Once inside the cell, the cargo can reach the cytoplasm and, in many cases, the nucleus, enabling expression or genome integration.

Microprojectile bombardment emerged in the late 20th century as a versatile method for transforming plant cells, particularly for species difficult to transform by other means. It is frequently referred to as biolistics. The technique has also been applied to cultured mammalian and fungal cells, though its use in clinical settings is limited by efficiency and safety considerations.

Applications include plant genetic engineering, functional genomics, and rapid testing of gene function. Advantages include the ability to transform tissues without protoplasts, applicability to a broad range of species, and rapid assessment of gene activity. Limitations include tissue damage, variable transformation efficiency, multiple-copy insertions, and the need for optimization of particle size, coating, and delivery parameters. Material choice (gold or tungsten beads) and DNA coating quality significantly influence outcomes.