Feedback Regulated Drug Delivery Systems MCQs With Answer
Feedback-regulated (closed-loop) drug delivery systems are designed to sense a physiological signal and automatically adjust drug release in real time, improving safety and efficacy. For M. Pharm students, mastering their principles involves understanding biosensors, stimuli-responsive materials, control algorithms, and clinical performance metrics. This quiz focuses on key concepts such as glucose-responsive insulin delivery, enzyme- and ROS-responsive platforms, negative versus positive feedback, device time constants, biofouling, and safety interlocks. You’ll also encounter design trade-offs like set-point selection, hysteresis to prevent oscillations, and strategies to manage sensor drift. Use these MCQs to test and refine your understanding of how modern closed-loop systems translate biochemical cues into precise, adaptive therapeutics.
Q1. Which feature fundamentally defines a feedback-regulated (closed-loop) drug delivery system?
- Real-time sensing of a biomarker with on-board control that adjusts drug release
- Constant zero-order drug release independent of physiological conditions
- Patient-activated dosing via a manual push-button
- Preprogrammed time schedule without any sensing element
Correct Answer: Real-time sensing of a biomarker with on-board control that adjusts drug release
Q2. Which of the following is a typical endogenous signal used to drive feedback-regulated delivery?
- External magnetic field strength
- Blood glucose concentration
- Ultrasound amplitude
- Ambient light intensity
Correct Answer: Blood glucose concentration
Q3. What core component enables a closed-loop system to “sense” the need for drug release?
- Permeation enhancer
- Biosensor (chemical or biochemical sensor)
- Imaging contrast agent
- Cryoprotectant
Correct Answer: Biosensor (chemical or biochemical sensor)
Q4. Which statement best differentiates closed-loop from open-loop drug delivery?
- Closed-loop systems alter dosing based on real-time measurements, whereas open-loop systems do not measure or adapt
- Closed-loop systems are always implantable, open-loop are always oral
- Closed-loop systems have higher dose capacity than open-loop systems
- Closed-loop systems can only deliver peptides, not small molecules
Correct Answer: Closed-loop systems alter dosing based on real-time measurements, whereas open-loop systems do not measure or adapt
Q5. Phenylboronic acid (PBA)-functionalized polymers are widely studied in which feedback application?
- Glucose-responsive insulin delivery
- pH-independent gastric delivery
- Light-triggered retinal drug delivery
- Magnetically targeted chemotherapy
Correct Answer: Glucose-responsive insulin delivery
Q6. In glucose oxidase (GOx)-based insulin systems, how is insulin release typically triggered?
- GOx converts glucose to gluconic acid, lowering local pH and triggering hydrogel swelling or degradation that increases insulin release
- GOx heats the device via exothermic reaction and melts a polymer barrier
- GOx produces oxygen bubbles that push insulin out mechanically
- GOx directly binds insulin and transports it across membranes
Correct Answer: GOx converts glucose to gluconic acid, lowering local pH and triggering hydrogel swelling or degradation that increases insulin release
Q7. What is a major long-term challenge for implantable biosensors used in closed-loop delivery?
- Acute photobleaching
- Biofouling and fibrotic encapsulation reducing sensor sensitivity
- Instantaneous thermal runaway
- Radiofrequency incompatibility with all wearables
Correct Answer: Biofouling and fibrotic encapsulation reducing sensor sensitivity
Q8. To prevent rapid on–off oscillations around the set-point in closed-loop delivery, designers often introduce:
- High amplifier gain without limits
- A hysteresis window around the set-point
- Randomized dosing schedules
- Fixed-time bolus overrides
Correct Answer: A hysteresis window around the set-point
Q9. Which safety strategy helps prevent overdose if a sensor erroneously reads a persistently high biomarker level?
- Increasing controller gain to respond faster
- Disabling all alarms to avoid nuisance alerts
- A hard cap on maximum delivery rate and total dose
- Removing flow restrictors to reduce backpressure
Correct Answer: A hard cap on maximum delivery rate and total dose
Q10. For effective feedback regulation, which alignment is most critical?
- Device color matching to skin tone
- Response time (sensing-to-release) aligned with biomarker dynamics and drug pharmacokinetics
- Battery chemistry matched to drug solubility
- Reservoir geometry matched to packaging dimensions
Correct Answer: Response time (sensing-to-release) aligned with biomarker dynamics and drug pharmacokinetics
Q11. Which is a clinically adopted example of closed-loop drug delivery?
- Osmotic oral pump for nifedipine
- Transdermal fentanyl patch
- Hybrid closed-loop “artificial pancreas” (insulin pump + CGM + control algorithm)
- Copper intrauterine device
Correct Answer: Hybrid closed-loop “artificial pancreas” (insulin pump + CGM + control algorithm)
Q12. In negative feedback drug delivery, which statement is accurate?
- Drug release amplifies deviations of the biomarker from the set-point
- Drug release opposes deviations, driving the biomarker back toward the set-point
- Drug release is unrelated to biomarker changes
- Drug release is fixed by circadian rhythm only
Correct Answer: Drug release opposes deviations, driving the biomarker back toward the set-point
Q13. In closed-loop systems, the “set-point” refers to:
- The maximum rate at which the pump can deliver drug
- The target biomarker value the controller aims to maintain
- The volume of the drug reservoir
- The mass of polymer in the hydrogel matrix
Correct Answer: The target biomarker value the controller aims to maintain
Q14. A key limitation of phenylboronic acid-based glucose sensing at physiological pH is:
- Excessive thermal sensitivity near 37°C
- High pKa of PBA reduces glucose binding at pH 7.4 unless modified
- Inability to be copolymerized with hydrophilic monomers
- Spontaneous polymer depolymerization in plasma
Correct Answer: High pKa of PBA reduces glucose binding at pH 7.4 unless modified
Q15. Concanavalin A (Con A)-based glucose-responsive systems face which biocompatibility concern?
- Severe phototoxicity under ambient light
- Immunogenicity and potential lectin toxicity
- Extreme radio-opacity requiring shielding
- Pyrophoric reactions with oxygen
Correct Answer: Immunogenicity and potential lectin toxicity
Q16. Which approach best mitigates sensor drift in long-term closed-loop delivery?
- Relying solely on factory calibration
- Periodic in situ calibration with drift-correction algorithms
- Using a larger drug reservoir
- Adding a colorimetric indicator for user inspection
Correct Answer: Periodic in situ calibration with drift-correction algorithms
Q17. Enzyme-responsive systems for inflammation often leverage elevated levels of which enzymes to trigger drug release?
- Matrix metalloproteinases (MMPs)
- DNases
- Amylases
- Pepsin
Correct Answer: Matrix metalloproteinases (MMPs)
Q18. A common chemical design for hypoxia-responsive drug release relies on:
- Thermal melting of a wax barrier
- Photolysis of coumarin linkers
- Reduction of nitroimidazole groups under low oxygen to cleave linkers
- Hydrolysis by gastric acid
Correct Answer: Reduction of nitroimidazole groups under low oxygen to cleave linkers
Q19. In proportional control for closed-loop delivery, the release rate is commonly set to:
- A constant value regardless of measurements
- Increase proportionally with the difference between sensed biomarker and set-point
- Decrease randomly to avoid tolerance
- Mirror the circadian rhythm without sensing
Correct Answer: Increase proportionally with the difference between sensed biomarker and set-point
Q20. Which metric is most clinically meaningful to assess the performance of a closed-loop system?
- Total volume of the device
- Percentage of time the biomarker remains within the target range
- Number of Bluetooth connections per day
- Device mass loss during storage
Correct Answer: Percentage of time the biomarker remains within the target range
