Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Development of the Implantable Bio-Artificial Kidney (iBAK)

1. In 2023, bioengineers successfully completed preclinical testing of an Implantable Bio-Artificial Kidney (iBAK). This compact, surgical implant is designed to be connected directly to a patient's circulatory system to mimic natural kidney function continuously. Unlike traditional hemodialysis, which requires patients to spend up to four hours, three times a week, connected to a bulky machine in a clinic, the iBAK is designed for long-term implantation. The device primarily functions to filter out metabolic wastes, such as urea, excess mineral ions, and excess water, ensuring these do not build up to toxic levels in the body.

2. The iBAK is surgically connected to the patient's iliac artery and vein. Blood enters the device under the pressure of the patient's own heartbeat, passing first through a high-efficiency silicon nanopore membrane (hemofilter) and then through a bioreactor containing living, cultured human renal tubule cells. The purified blood is then returned directly to the venous system.

3. To maintain the viability of the living tubule cells within the bioreactor, the iBAK relies on a steady nutrient supply and temperature control, which are monitored by microchips. These electronic monitoring components are powered by an external battery pack worn on a chest harness, which transmits power transcutaneously (through the skin) via induction coils. The battery pack must be replaced or recharged every eight hours.

4. Clinical coordinators noted that during trials, the concentration of blood urea nitrogen in subjects remained within healthy limits. Continuous filtration meant that patients did not experience the rapid shifts in blood pressure and cellular hydration that typically occur during rapid, intermittent hospital dialysis. Additionally, patients reported a significantly improved quality of life, as they were able to resume normal work and moderate physical activity. During periods of heavy physical activity or high-protein meals, the rate of filtration through the silicon membrane can be adjusted by a wearable control unit.

5. The iBAK represents a significant leap forward because it operates continuously and is completely internal, eliminating the risk of line infections associated with external catheters. With a critical shortage of donor kidneys for transplantation, this implantable device offers a viable long-term solution for patients who are unsuitable for transplant surgery or who face years on transplant waiting lists.

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