Micro injection is an efficient way of delivering genetic materials into cells for a variety of applications. Unlike other physical and chemical transformation methods, microinjection directly delivers foreign DNA to host cells without a mediator (like a plasmid DNA particle). This is achieved by the use of extremely small bore glass needles, usually with an outer diameter of less than 0.2 um, which are used to insert foreign DNA into cell membranes, where it can be integrated into DNA and/or expressed in a regulated manner.
Traditional methods to deliver molecules into cells are expensive, time consuming, require experienced operators and can be limited in their ability to target specific cells. Microinjection, on the other hand, is fast and affordable, does not require the use of chemicals, and can be performed by any trained technician.
However, if not done properly, microinjection can result in irreversible damage to the host plant. This can be caused by improper needle placement or by injecting too much material, both of which can lead to tree death or discoloration. In addition, trunk wounds from injection can be difficult to heal, allowing for disease infection. For these reasons, it is important for anyone considering offering injection services to first understand the benefits and limitations of this treatment method, as well as to chart a course that will help them achieve optimal results with the least amount of harm to the trees they are treating.
To address these concerns, a new passive microinjection method using pulsating flow patterns has been developed within a T-junction microfluidic system. This technique allows for a highly accurate and quantitative control of injection parameters. This can be achieved through the proper selection of four key coefficients, whose combination guarantees the success of the microinjection process.
This system also allows the use of much lower concentrations of reagents than previous methods, which can reduce costs and reduce the likelihood of chemical-induced damage to the plants being treated. In addition, this technique offers a higher rate of success than other active methods such as electroporation and magnetic tweezers.
The T-junction microfluidic device consists of three components: a reservoir, a flow control valve and an injection station. The reservoir holds water, and the flow control valve is connected to a micropump that drives a constant flow of water into the injection station. The pump is attached to a micromanipulator, which in turn controls the movement of the needle during the injection process. The value of the coefficient l must be carefully adjusted to harmonize the pulsating flow patterns with the injection, resting and pulling steps of the cycle. In order to prevent damage to the double emulsion, this coefficient ensures that a high shear stress is exerted on Droplet from the pulsating flows but that the inertial force of the flow is not so large as to rupture the double emulsion or to pull the injected cell off the microneedle (Fig. S1a). In fact, a pair of intense vortices are created around Droplet during this interaction phase (Fig. S1b, c).