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Microencapsulation

Microencapsulation. Eric Lee, Yik Ning Wong, Miguel Benson, John Harrison, Albert Kwansa Client: Dr. Craig Atwood Advisor: Professor William Murphy. H ypothalamus. -. -. Target Cells. GnRH. LH & FSH. Testosterone. +. Anterior P ituitary. -. -. FSH. LH. Testosterone. Inhibin. +.

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Microencapsulation

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  1. Microencapsulation Eric Lee, Yik Ning Wong, Miguel Benson, John Harrison, Albert Kwansa Client: Dr. Craig Atwood Advisor: Professor William Murphy

  2. Hypothalamus - - Target Cells GnRH LH & FSH Testosterone + Anterior Pituitary - - FSH LH Testosterone Inhibin + + Testosterone Male Gonads Leydig Cells Sertoli Cells Background - HPG Axis

  3. Background – Hypogonadism • Hypogonadism • Reduction or loss of gonad function • Diminished testosterone production by leydig cells • Approach: Replace this steroidogenic function via leydig cell transplantation.

  4. Challenges with traditional cell transplantation Immune Response Advantages of microencapsulation Cell entrapment Immunoisolation Selective transportation Sustained release of hormones Micro-scale size reduces diffusion distance Polyethylene glycol diacrylate (PEGdA) Cell Transplantation

  5. Degradation Size exclusion via mesh size LH, FSH, O2, Nutrients Antibodies Testosterone, Wastes Microcapsule Parameters Biocompatibility Microcapsule Size

  6. Last Semesters Work • UV exposure time upper limit = 15 min • Theoretical max gel thickness = 250 μm

  7. Current Goal • Determine effect on cell viability and testosterone production due to: • Gel thickness………………… • UV exposure…………………. • RGD adhesion……………….. Calculated test range: 25-250 μm 0-15 min 0-1 mol%

  8. UV Exposure Time • Previous constraints • Must be <15 min for cells to survive • Further constraints • Find minimum time to gel completely • Degree of swelling gives measure of degree of polymerization

  9. Swelling Experiment • Incomplete polymerization • Less X-links • More room to swell • Complete polymerization • Max links crossed • Decreased swelling capability • Observed at t ≥ 13 min

  10. Capsule Radius • Long Term implementation • Theoretical maximum radius = 250 m • Equilibrium Swelling Ratio = 3.80 • Maximum initial capsule radius = 160m 160m 250m

  11. Hydrogel Thickness • Simulation of capsule radius • Post swell thickness = 25m ~ 250m • Pre swell thickness = 25m ~ 175m Tape spacers Microscope slides PEGdA Hydrogel Preset thickness

  12. Transducers D D PEGdA Time = 2*Distance / Speed of sound in water Ultrasound • Determination post swell thickness and thickness of hydrogel sandwich • Confirm swelling calculation

  13. Disadvantages of Ultrasound • Similar density of hydrogel and water • Contrast agent • Backscattering • Microscope slide surface treatment (Sigmacote) Transducer D PEGdA PEGdA PEGdA w/o Contrast Agent PEGdA w/ Contrast Agent

  14. RGD Adhesion Molecule • Promote cell adhesion within PEGdA capsule RGD peptide PEGdA biomaterial Cell

  15. KEY Biomaterial Cell protrusion Integrin cell receptor RGD peptide sequence Spacer sequence Without Spacer With Spacer RGD & Spacer Sequence • N-term-CGGGR GDSP-C-term

  16. Questions?

  17. Mathematical Calculations Equal swelling in all dimension • T = (Swelling Ratio )1/3 x t T t T* t* t T Volume = t x t x t (Swelling Ratio)(Volume) = T x T x T

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