Orally Delivered Nanoparticles For Brain Delivery

2,001 views

Published on

Original Research: Surface-engineered nanoparticles for targeted delivery of therapeutic peptides to brain tissue

  • Be the first to comment

Orally Delivered Nanoparticles For Brain Delivery

  1. 1.  The global market for drugs for the central nervous system (CNS) is greatly under-penetrated, and would have to grow by >500% just to equal the cardiovascular drug market.  More than 98% of the newly developed agents for CNS do not cross BBB.  Molecules should possess low molecular weight (<500 Da) and high lipophilicity in order to cross blood-brain barrier (BBB).  There are only a few diseases of the brain that are currently treated by CNS drugs. › Only affective disorders, insomnia, pain, and epilepsy respond to small molecules › Most other brain diseases such as Alzheimer’s,Parkinson’s,Brain Cancer, Stroke, Neuro-AIDS etc do not respond to small molecules. 2
  2. 2.  Recently developed large molecules such as therapeutic proteins, peptides, genes, monoclonal antibodies, cannot cross BBB.  Development of drugs for brain is incomplete without a parallel approach in brain drug delivery. Ref: Pardridge, W.M. Brain Drug Targeting: The Future of Brain Drug Development, Cambridge University Press, 1, (2001), pp 3- 9. 3
  3. 3.  Oral bioavailability of proteins and peptides is severely limited due to the epithelial barriers of the GIT and degradation by digestive enzymes.  GI passage of particles can be achieved by formulation of fine size ranges of approximately below 200 nm.  A Nano-size range favors uptake through › Absorptive Enterocytes › Intestinal M cells  Also, a size range below 200 nm favors escape from spleenic filtration effects thereby enhancing circulation half-life of nanoparticles. 4
  4. 4.  Polymeric nanoparticles can allow loading of such molecules within a polymeric matrix, protecting from enzymatic degradation and hydrolysis, as well as targeting to brain tissue.  However, application of nanoparticles as oral drug delivery systems are restricted due to their › Limited absorption across GIT. › Short circulation half-life. (The peptide drug chosen for this study is dalargin, a hexapeptide with amino acid sequence Tyr-D-Ala-Gly-Phe- Leu-Arg which does not cross the BBB. It is an Leu-Enkephalin analog which binds with opioid receptors in brain and causes central analgesia) 5
  5. 5.  Nanoparticles can be “double-coated” with a combination of Tween 80 and PEG 20,000 successively to achieve “stealth” targeting properties. Role of Tween 80  A Tween 80 coating over a polymeric nanoparticle leads to the adsorption of Apo lipoprotein E (Apo E) from plasma upon the nanoparticle surface.  Such nanoparticles interacts with Low Density Lipoproteins (LDL) receptors in BBB and reaches the brain interior by endocytic uptake mechanism.  Nanoparticles degrade in brain interior and peptide is released. 6
  6. 6. Role of PEG 20,000  Poly (ethylene) glycol (PEG) is known to protect labile drugs against enzymatic degradation in GIT.  Higher molecular weight PEGs such as PEG 20,000, forms a protective “brush” against the digestive enzymes.  High molecular weight PEGs also provides “dysopsonic” effect against macrophageal clearance in the blood circulation. 7
  7. 7. 8
  8. 8. 9
  9. 9.  Emulsion (Anionic) polymerization  Medium (pH 2.5, 0.01N HCl) containing Dextran 70 (1.5%) as an emulsifier.  Polymerization for 4 hours with constant magnetic stirring at 8,000 rpm.  Medium was neutralized using 0.1 N NaOH until the final pH reached 7.0  Size excluded by multi-filtration steps using successive filters of 5 µ, 1.2 µ and 0.7 µ pore size diameters. 10
  10. 10.  Unreacted monomers and agglomerations removed by 3 cycles of washing and ultracentrifugation at 76,500 g for 1 hour.  Nanoparticles collected as wet pellets.  Immediately kept in lyophilizer at -40ºC and 130 × 10-4 mbar for 12 hours for freeze drying.  Finally, nanoparticles were obtained as free flowing, white powder and stored at 4ºC for further use.  The nanoparticle yield was 23% w/w.  Entrapment efficiency (EE %) was found to be 39.84 ± 4 % w/w 11
  11. 11. 12 Formulation Codes: Coatings with: Tween 80 (%) Coatings with: PEG 20,000 (%) T0P0 0 0 T2P0 2 0 T1.5P0.5 1.5 0.5 T1P1 1 1 T0.5P1.5 0.5 1.5 T0P2 0 2 T2P2 2 2
  12. 12. 13  An average diameter of 100 nm with a polydispersity index of 0.018 obtained for the optimum formulation.
  13. 13. -25 -20 -15 -10 -5 0 T0P0 T2P0 T1.5P0.5 T1P1 T0.5P1.5 T0P2 T2P2 PBCA-NDS Formulations ZetaPotentials(mV) 14
  14. 14. 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 Time (hours) %DrugRelease T0P0 T2P0 T1.5P0.5 T1P1 T0.5P1.5 T0P2 T2P2 15
  15. 15. 16 0 10 20 30 40 50 60 70 80 90 100 T0P0 T2P0 T1.5P0.5 T1P1 T0.5P1.5 T0P2 T2P2 PBCA-NDSFormulations %DrugRemaining 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 Time (hours) %DrugRemaing T2P2 T0P0
  16. 16. 0 10 20 30 40 50 60 70 80 90 100 T0P0 T2P0 T1.5P0.5 T1P1 T0.5P1.5 T0P2 T2P2 PBCA-NDSFormulations %DrugRemaining 17 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 Time (hours) %DrugRemaining T2P2 T0P0
  17. 17. 18 Formulation Code Summary C1 PBS solution {Control 1} C2 PBS + Tween (2%) {Control 2} C3 PBS + PEG (2%) {Control 3} C4 PBS + Tween (2%) + PEG (2%) {Control 4} C5 PBS + Drug {Control 5} C6 PBS + Drug + Tween (2%) {Control 6} C7 PBS + Drug + PEG (2%) {Control 7} T2P2-N PBS + Drug + Tween (2%) + PEG (2%) + No nanoparticles present T0P0 PBS + Drug + Nanoparticles + Tween (0%) + PEG (0%) T2P0 PBS + Drug + Nanoparticles + Tween (2%) + PEG (0%) T1.5P.5 PBS + Drug + Nanoparticles + Tween (1.5%) + PEG (0.5%) T1P1 PBS + Drug + Nanoparticles + Tween (1%) + PEG (1%) T.5P1.5 PBS + Drug + Nanoparticles + Tween (0.5%) + PEG (1.5%) T0P2 PBS + Drug + Nanoparticles + Tween (0%) + PEG (2%) T2P2 PBS + Drug + Nanoparticles + Tween (2%) + PEG (2%) T2P2 + A PBS + Drug + Nanoparticles + Tween (2%) + PEG (2%) + Naltrexone HCl
  18. 18. 19 0 20 40 60 80 100 0 15 30 45 60 75 90 105 120 Time Points (mins) %MPE T2P2 T2P2+Anta T0P2 T.5P1.5 T1P1 T1.5P.5 T2P0 T0P0 T2P2-Nano (*) = p < 0.05, compared with T0P0 * * *
  19. 19. 0 20 40 60 80 100 7.5 15 22.5 30 37.5 45 52.5 Dose (mg/kg) %MPE 20
  20. 20.  Double-coated PBCA-NDSs with overcoats of Tween 80 and PEG 20,000 represent a feasible method to deliver and target peptides to brain via the oral route.  Coating of nanoparticles with 2% Tween and 2% PEG represents the optimal formulation for PBCA nanoparticulate system.  PBCA-NDSs with average diameter of 100 nm represents a satisfactory size for oral and targeted peptide delivery to the brain. 21

×