Continuous Drug Infusion System in Mouse Model: A Surgical Procedure to Implant Micro-osmotic Pump Infusion System in the Mouse Brain for Continuous Drug Delivery

Drug delivery into the brain through cerebrospinal fluid, or CSF, is limited by the blood-brain barrier, or BBB, which significantly reduces the drug concentration. A micro-osmotic pump-based brain infusion system is a small implantable device that overcomes BBB, enabling continuous drug delivery into the brain.

To begin, take a micro-osmotic pump coated with an artificial CSF or aCSF, a vehicle for drug delivery. Now, fill the pump with the desired drug solution. Next, take a brain infusion assembly comprising a catheter attached to an infusion needle. Fill the assembly with the drug. Finally, connect this assembly to the micro-osmotic pump to complete the brain infusion system.

Now, prep an anesthetized mouse on a stereotactic apparatus. Remove the outer skin of the head and disinfect the exposed skull. Using a microdrill, create a hole in the skull to form a passage for the infusion system. Open the skin behind the neck region and place the micro-osmotic pump underneath. Simultaneously, insert the infusion needle into the drilled hole.

The needle penetrates the meninges, and reaches the ventricles to infuse the drug into the brain. Now, apply a suitable adhesive gel to fix the needle. Then, detach the top of the needle. Allow the mouse to recover for further experiments.

One day before the surgery, prepare brain osmotic pumps by using a 1-milliliter syringe and blunt-head needle to fill the pumps with artificial cerebrospinal fluid, or aCSF. Then, immerse the pump in aCSF and place it on a shaker for gentle overnight shaking. On the following day, remove the aCSF from the pump, and fill it completely with previously prepared drug solution diluted in aCSF, until the excess leaks out.

Then, use surgical scissors to cut the catheter tubes to desired length. Using a blunt-end brain infusion needle, attach the tubes to the brain infusion kit. Then, fill the tubes in the infusion kit with the drug solution. After assembling the kit, attach it to the micro-osmotic pump. Finally, to prevent the pump from drying out, immerse the osmotic pump brain infusion setting in aCSF within a sterilized 50-milliliter tube.

To start the surgery, mount and fix the head of an anesthetized mouse onto a stereotactic apparatus. Using a pair of surgical scissors and pincers, cut open the outer skin covering the skull. Then, use iodine to clean the peripheral skull. Next, use a pair of blunt-head scissors near the neck region to separate the outermost layer of skin from the subcutaneous skin for the osmotic pump brain fusion set implantation.

Use the stereotactic apparatus to mark the infusion point with reference to the brain map. Use a nail drill to drill a hole around the area marked on the skull, being careful not to break the mouse meninges and blood vessels. Then, place the micro-osmotic pump brain fusion set containing the drug of interest, or aCSF, as a control under the skin behind the neck region.

To infuse the drug into the brain, insert the brain infusion needle into the drilled hole. Use surface desensitizing gel to fix the needle in place on the skull, and wait until the glue dries. Cut off the projecting part on top of the needle.