A.A. Huth, C. Flanagan, M. Michalski, A. RievesHuth, C. Flanagan, M. Michalski, A. Rieves Client: W. John Kao, Ph.D, School of Pharmacy & Department of Biomedical EngineeringClient: W. John Kao, Ph.D, School of Pharmacy & Department of Biomedical Engineering

Advisor: Kristyn Masters, Ph.D, Deparment of Biomedical EngineeringAdvisor: Kristyn Masters, Ph.D, Deparment of Biomedical Engineering

A.A. Huth, C. Flanagan, M. Michalski, A. RievesHuth, C. Flanagan, M. Michalski, A. Rieves Client: W. John Kao, Ph.D, School of Pharmacy & Department of Biomedical EngineeringClient: W. John Kao, Ph.D, School of Pharmacy & Department of Biomedical Engineering

Advisor: Kristyn Masters, Ph.D, Deparment of Biomedical EngineeringAdvisor: Kristyn Masters, Ph.D, Deparment of Biomedical Engineering

Results Results Results Results

ReferencesReferencesReferencesReferences

Future WorkFuture WorkFuture WorkFuture Work

BackgroundBackgroundBackgroundBackground

MotivationMotivationMotivationMotivation

MethodsMethodsMethodsMethods

AbstractAbstractAbstractAbstract Spray Bottle DesignSpray Bottle DesignSpray Bottle DesignSpray Bottle Design

INTERPENETRATING NETWORKS INTERPENETRATING NETWORKS FOR DELIVERY SYSTEMSFOR DELIVERY SYSTEMS

INTERPENETRATING NETWORKS INTERPENETRATING NETWORKS FOR DELIVERY SYSTEMSFOR DELIVERY SYSTEMS

•Prepackaged• Pre-measured amounts of Gelatin, PEGda, and photoinitator powders contained in spray bottle.•Additional bottle containing pre-measured citrate buffer solution•Simple mixing procedure

•Bottle•Dark Bottle & Removable Sticker

•Provides for completly dark storage environment for photoinitiator preservation

•Dissolution Strip•Allows to see extent of dissolution without compromising photoinitator

•Clear Bottom•Second means of observing extend of dissolution

•Wide Diameter Bottle•Offers most even mixing

•Wide Diameter Straw•More even distribution during spraying

Problem StatementProblem StatementProblem StatementProblem Statement

Design ConstraintsDesign ConstraintsDesign ConstraintsDesign Constraints

For all tests, a 10% solution was achieved using 2g of gelatin and 2mL of solvent. The chart below outlines the different combinations of bloom strength gelatin, surfactants, and solvents used as well as the general process for creating an optimal IPN.

Our goal was to create a novel delivery mechanism to reconstitute the components of an interpenetrating network (IPN).

•Mixing procedures should be straightforward to minimize human error.

•Final solution should have a uniform consistency and viscosity suitable for spray application.

•Final solution should be cured within 60 seconds under UV light after application to wound.

•Final solution or any of the initial chemical components should not inflict any harm on the patient or medical personnel making or applying the IPN.

Interpenetrating networks composed of gelatin cross-linked with PEG diacrylate provide a promising solution to increase healing time for large surface area wounds; however, the current reconstitution and administration methods of this product are clinically undesirable. The goal of this project was to create a novel mechanism to reconstitute the components of an interpenetrating network in attempts to achieve long-term storage and successful IPN delivery. After much testing, a final solution of 20mL citrate buffer, two grams of 90-110 bloom gelatin, and ___ I-2959 was determined to provide the best dissolution. Alterations were also made in the design of the spray bottle to improve administration techniques. Despite these findings, further testing must be done.

•Large surface area and chronic non-healing wounds significantly impair the quality of life for millions of people in the United States (Harding et al, 2002).

•Interpenetrating networks (IPNs) created by our client, Professor W. John Kao, provide a promising solution to increase healing time for these types of wounds; however, the current reconstitution and administration methods of this product are clinically undesirable.

Product Application methods Advantages Disadvantages

TransCyte Cryogenically frozen, applied in sheets

Temporary until autograft is possible

Must be cryogenically frozen until use, then thawed

Silver-Coated

Foam, Topical, typical dressing

Broad-spectrum anti-microbial effects

Does not help heal wounds

Orcel In Sheets Skin Replacement Collagen Derived Expensive

Dermagraft Skin Replacement Patients’ cells infiltrate matrix to heal wounds

Expensive

Competing ProductsCompeting ProductsCompeting ProductsCompeting Products

Bifunctional PEG Linkers

Covalently Linked Therapeutic(s) and/orCell Adhesion Ligands

Soluble Therapeutic(s)

BiodegradableGelatin Backbone

PEG-diacrylate(2-3.4 kDa )

*Kao, W.J

Benefits• Moist healing environment• Conforms to irregular wounds

Gelatin is a protein derived from collagen. It contains various functional groups, which give different forms distinct properties.

What is an IPN?

Non-covalent physical interactions which form a gel matrix. Our client’s therapeutic IPN can incorporate various drugs and cure under UV light serve as effective wound dressings.

• Covers large surface areas• Delivers drug cocktails• Very Biocompatible

Gelatin Solution

Bloom Strength Surfactants Solvents

Final Solution

PEG-dAPhotoinitiator

IPN

Spray Bottle UV-Light

90-110, 175, 300Tween-20, SDS

pH 2,14PBS, Acetate-Citrate Buffer

60°, Room Temp H2O

1-2959, DMPA 2.1kD, 3.4kD

Nozzle TypeAbility to see sol’n

Spray pattern

WavelengthCuring Time

Intensity

Gelatin Bloom

Strength

Dissolution in 10%

solution 

Gelatin Bloom

Strength

Dissolution in 10%

solution

60 °C H2O  Acetate/Citrate

buffer

90-125 +++   90-125 +++

175 +++   175 ++

300 +++   300 ++

Room temp. H2O   HEPES buffer

90-125 --   90-125 +

175 --   175 +

300 --   300 +

Phosphate buffer   pH 13.5

90-125 --   90-125 +++

175 --   175 +++

300 --   300 +++

Tween-20 in PBS   pH 1

90-125 --   90-125 +++

175 --   175 +++

300 --   300 +++

Table Key

+++ Full Dissolution ++ Partial Dissolution

+ Dispersion -- Phase Separated

Effect of Bloom Strength on Gelatin Dissolution in Citrate Buffer Over Time

0%

100%

200%

300%

400%

500%

0 1 2 3 4 5 6

Time (min)

Dis

solu

tio

n d

iffe

ren

ce f

rom

H 2

0

90 bloom

300 bloom

Water is considered to be optimally dissolved, so greater percentage values are less favorable.

•Design stirring apparatus within spray bottle to aid in dissolution

•Design bottle to contain both liquid and solid components of the IPN

•Measure sol fraction

•Dialyzation/neutralization of gelatin in extreme acids and bases followed by lyophilization. Gelatin fragments combined with non-fragmented gelatin would then be reconstituted in H2O.

AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements•Kristyn Masters, Ph.D., UW- Madison, Department of Biomedical Engineering•W. John Kao, Ph.D., UW-Madison, School of Pharmacy•Samuel Gellman, Ph.D., UW-Madison, Department of Chemistry• Tracy Williamson, UW-Madison, School of Pharmacy•Dave Schmidt, UW-Madison, School of Pharmacy

(Ehrenreich & Ruszczak, 2006)

Ehrenreich, M., & Ruszczak, Z. 2006. Update on Tissue Engineered Biological Dressings. Tissue Engineering. 12: 2407-2424.