Drug delivery and biomarker access devices

A method of delivering a drug into a brain of a patient and accessing biomarkers from the brain, the method comprising:

• implanting a drug delivery device into the patient, wherein the drug delivery device comprises;
• a first reservoir;
• a second reservoir;
• a perfusion catheter extending from the second reservoir and in fluid communication with the second reservoir;
• and
• a return catheter extending from the first reservoir and in fluid communication with the first reservoir,
• wherein the first and second reservoirs are independently biased and fluidly segregated, such that fluid moves in a single directional flow path without recirculation between the first reservoir and the second reservoir;
• wherein the implanting comprises positioning the first reservoir and the second reservoir between a scalp and a skull of the patient and extending the perfusion catheter and the return catheter into the brain;
• compressing the first reservoir such that a fluid in the first reservoir is caused to flow into the second reservoir, wherein the fluid that is caused to flow into the second reservoir by compressing the first reservoir causes expansion of the second reservoir;
• after the expansion of the second reservoir, allowing the fluid to flow out of the second reservoir and into the perfusion catheter as a result of a natural bias of the second reservoir to be in an unexpanded configuration, wherein at least some of the fluid that flows into the perfusion catheter exits from the perfusion catheter into the brain;
• and
• after the compressing the first reservoir, allowing the first reservoir to re-expand as a result of a natural bias of the first reservoir to be in an expanded configuration, wherein at least some of the fluid from the brain is drawn into the return catheter and flows from the return catheter into the first reservoir as a result of the re-expansion of the first reservoir.