Biological approaches for SR/CR formulation MCQs With Answer

Biological approaches for SR/CR formulation MCQs With Answer

Biological approaches to sustained/controlled release (SR/CR) leverage the body’s own physiology—enzymes, receptors, transporters, microenvironmental triggers, and biodegradable matrices—to modulate drug exposure over time. For M.Pharm students, mastering these concepts bridges formulation science with pharmacokinetics and targeting. This quiz explores key strategies such as prodrug design, microflora-triggered colon delivery, mucoadhesion, PEGylation, albumin-binding, receptor-mediated transcytosis, and biodegradable depots (e.g., PLGA microspheres). It also covers microenvironment-responsive systems like glucose-triggered insulin release and enzyme-cleavable hydrogels, as well as biological fate of liposomes and nanoparticles (RES uptake, EPR effect). Work through these MCQs to consolidate mechanisms, examples, and design parameters that translate biological phenomena into precise SR/CR performance.

Q1. Which statement best defines “biological approaches” to SR/CR drug delivery?

• Leveraging endogenous processes (enzymes, receptors, cells, and microenvironments) to modulate drug release and disposition
• Using only non-biodegradable polymers to slow diffusion of drugs
• Relying exclusively on osmotic pressure for drug release
• Excluding the influence of physiology to maintain formulation robustness

Correct Answer: Leveraging endogenous processes (enzymes, receptors, cells, and microenvironments) to modulate drug release and disposition

Q2. Which polymer class is predominantly surface-eroding and can approximate zero-order release profiles in vivo?

• Polyanhydrides
• Poly(lactic-co-glycolic acid) (PLGA)
• Polyvinyl alcohol (PVA)
• Hydroxypropyl methylcellulose (HPMC)

Correct Answer: Polyanhydrides

Q3. In PLGA-based depots, which change generally prolongs degradation time and sustains release?

• Increasing lactide content (higher lactic:glycolic ratio)
• Decreasing molecular weight of the polymer
• Using acid-terminated rather than end-capped PLGA
• Increasing glycolide content above lactide

Correct Answer: Increasing lactide content (higher lactic:glycolic ratio)

Q4. Sulfasalazine achieves colon-specific delivery through which microbially triggered chemical feature?

• Azo (–N=N–) linkage reduced by bacterial azoreductase
• Acetal linkage cleaved by gastric acid
• Ester linkage cleaved by pancreatic lipase in the duodenum
• Disulfide linkage reduced by hepatic glutathione

Correct Answer: Azo (–N=N–) linkage reduced by bacterial azoreductase

Q5. Which polymer exhibits mucoadhesion primarily due to its cationic nature at physiological pH, enhancing residence time for SR?

• Chitosan
• Hydroxypropyl cellulose (HPC)
• Ethylcellulose
• Polyvinylpyrrolidone (PVP)

Correct Answer: Chitosan

Q6. PEGylation prolongs the circulation half-life of nanocarriers primarily by which mechanism?

• Reduced opsonization and RES uptake via hydrophilic steric shielding and increased hydrodynamic size
• Enhanced active transport through P-glycoprotein
• Facilitated renal filtration through decreased hydrodynamic radius
• Increased binding to fibrin for intravascular retention

Correct Answer: Reduced opsonization and RES uptake via hydrophilic steric shielding and increased hydrodynamic size

Q7. Long-acting analogs like insulin detemir use which modification to achieve albumin binding and sustained action?

• Lipidation with a long-chain fatty acid
• Phosphorylation of serine residues
• Glycosylation with mannose
• Sulfonation of tyrosine residues

Correct Answer: Lipidation with a long-chain fatty acid

Q8. Conventional (non-stealth) liposomes administered intravenously are predominantly sequestered by which organ due to RES uptake?

• Liver
• Kidney
• Thyroid
• Skin

Correct Answer: Liver

Q9. SR/CR from PLGA microspheres administered intramuscularly is generally governed by which mechanism?

• Combined diffusion through pores and polymer biodegradation/erosion
• Purely osmotic pumping independent of polymer erosion
• Ion-exchange with extracellular cations
• Photolysis of the polymer backbone in vivo

Correct Answer: Combined diffusion through pores and polymer biodegradation/erosion

Q10. Which trigger enables in situ gelation of certain ophthalmic systems (e.g., gellan) to sustain drug release on the eye?

• Divalent cations (e.g., Ca2+) in tear fluid inducing gelation
• Ambient light causing rapid photopolymerization
• Blood oxygen saturation controlling crosslinking
• Shear-thickening under blinking to form a rigid gel

Correct Answer: Divalent cations (e.g., Ca2+) in tear fluid inducing gelation

Q11. In glucose-responsive insulin delivery, what is the role of glucose oxidase?

• Converts glucose to gluconic acid, lowering pH and triggering polymer response to release insulin
• Cleaves insulin to a less active form at high glucose
• Oxidizes insulin to increase its receptor affinity
• Generates ATP to fuel micro-pumps in the device

Correct Answer: Converts glucose to gluconic acid, lowering pH and triggering polymer response to release insulin

Q12. L-valyl ester prodrugs like valacyclovir utilize which transporter to enhance absorption and modulate exposure?

• PepT1 (H+-coupled oligopeptide transporter)
• GLUT4 (insulin-sensitive glucose transporter)
• OCT2 (organic cation transporter)
• P-glycoprotein (ABCB1)

Correct Answer: PepT1 (H+-coupled oligopeptide transporter)

Q13. Which natural polymer is specifically degraded by colonic microbial enzymes and used for colon-targeted SR systems?

• Pectin
• Eudragit S100
• Ethylcellulose
• Polycaprolactone

Correct Answer: Pectin

Q14. To exploit the EPR effect for tumor targeting while avoiding rapid renal clearance, which particle size range is generally optimal?

• 50–150 nm
• 5–10 nm
• 500–1000 nm
• 1–2 μm

Correct Answer: 50–150 nm

Q15. Fc-fusion biologics achieve prolonged half-life primarily through interaction with which receptor and mechanism?

• Neonatal Fc receptor (FcRn) mediating pH-dependent endosomal recycling back to plasma
• TLR4 via NF-κB activation and decreased clearance
• EGFR with receptor downregulation
• LDL receptor via clathrin-mediated degradation

Correct Answer: Neonatal Fc receptor (FcRn) mediating pH-dependent endosomal recycling back to plasma

Q16. “RBC hitchhiking” of nanoparticles provides what primary advantage for SR/CR or targeting?

• Prolonged circulation and reduced immune clearance by camouflaging on erythrocyte surfaces
• Immediate activation of cytotoxic T cells against the carrier
• Enhanced renal filtration due to smaller apparent size
• Rapid accumulation in bone due to calcium affinity

Correct Answer: Prolonged circulation and reduced immune clearance by camouflaging on erythrocyte surfaces

Q17. Which strategy best minimizes initial burst release from biodegradable microspheres?

• Using high–molecular weight, end-capped PLGA and reducing initial porosity during fabrication
• Adding pore formers to increase internal water channels
• Maximizing drug solubility in the external aqueous phase
• Using strong surfactants to aggressively extract solvent

Correct Answer: Using high–molecular weight, end-capped PLGA and reducing initial porosity during fabrication

Q18. Enzyme-responsive hydrogels for tumor-targeted release often incorporate linkers cleavable by which enzymes?

• Matrix metalloproteinases (e.g., MMP-2/9)
• Amylases in saliva
• Renin in plasma
• Carbonic anhydrase in erythrocytes

Correct Answer: Matrix metalloproteinases (e.g., MMP-2/9)

Q19. Which ligand is commonly used to enable receptor-mediated transcytosis across the blood–brain barrier for nanoparticle delivery?

• Transferrin
• Folic acid
• Mannose
• Hyaluronic acid

Correct Answer: Transferrin

Q20. Which polymer forms Ca2+-crosslinked “egg-box” hydrogels that sustain drug release in physiological ionic environments?

• Sodium alginate
• Hydroxypropyl methylcellulose (HPMC)
• Polyvinylpyrrolidone (PVP)
• Polylactic acid (PLA)

Correct Answer: Sodium alginate

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