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Aqueous Nanodispersions of Biodegradable Polyesters forNanofiber Preparation by Electrospinning

Andreas Greiner

Philipps-Universität Marburg, Department of ChemistryHans-Meerwein str, 35032 Marburg, Germany

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From water processable to water stable

Processing from water

Nanomaterial

Water stable???

Biodegradable Polyesters

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The visionProtection by mating disruption with pheromonesfrom artificial dispensers

Requirements- Dispensers have to create homogenous phermone cloud- Dispensers have to be biodegradable- Dispensers have to be stable during release of pheromone – suspension electrospinning- Dispensers have to release pheromone steadily

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The conceptUse of electrospun pheromone releasing nonwovens

Nanofiber nonwovensPheromone releasingmicrocapsules

The green approach

•Water based formulation

•Water stable nonwoven

•Degradable nonwoven

•Phermone release

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In brief about nonwovens by eletrospinningA coating technique

Fiber diameters 1 – 10.000 nm

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From lab scale to technical scale

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Polycaprolactone

Polymers for electrospinning

Polylactide

Nylon 66 PMMA

Nylon 6

PolystyrenePolyethylene

Polypropylene

Silk

PET

TPU Polyethyleneoxide

PolyvinylalcoholPolyvinylpyrollidonPolyacrylic acid

Chitosan

DNA

PolycarbonatePolyethersulfone

Polyimide

Fibrinogen

Collagen

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Take home messageSo many options by electrospinningfor novel nanofiber nonwovens

Reviews: Greiner, Wendorff, Angew. Chem. Int. Ed. 2007, 46, 5670Agarwal, Wendorff, Greiner, Polymer 2008, 49, 5603 (Biomed.)Agarwal, Greiner, Wendorff, Adv. Funct. Mater. 2009, 19, 1 Agarwal, Greiner, Wendorff, Adv. Mater. 2009, 21, 1 (Tissue Eng.)Agarwal, Wendorff, Greiner, Macromol. Chem. Rapid Commun. 2010, 31, Agarwal, Greiner, Special Topic Issue on Eletrospinning, Polym. Adv. Techn., 2011

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Nanofiber nonwovens ???Pheromone releasingMicrocapsules???

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How to electrospin for water stable biodegradablepolymers from water?

Well established biodegradable polymers:Aliphatic polyesters (polylactide, PCL…)

Problem: soluble only in hazardous solventsNo electrospinning on fields possible

The possible solution:Suspension electrospinning of secondary suspensions of biodegradable polyesters

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How to get secondary suspensions of biodegradablepolymers?

Water soluble blockBiodegradable

hydrophobic block

Suspensions bymicell formation

H2O

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Synthesis diblock copolyester

Mn = 6400 (GPC – PS standards Mw / Mn = 2.1Insoluble in waterTm = 58 °C

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Secondary dispersion of the diblockcopolyester in water

Follow protocol of solvent displacement method• Dissolve polyester and Brij78 (10%) in actone• Add water• Apply ultrasound

Stable suspensionSolid content: 2.5 %

Too low for electrospinning

112 nm

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Up-concentration of the secondary dispersionDialysis of suspension

Dialysistube

Suspensionof polyester

Water+ PVA(16%)

Set-up of dialysis

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Up-concentration of the secondary dispersionDialysis of suspension

Stable suspensionSolid content: 16 %

Good for electrospinning

109 nm

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Take home message

Aliphatic water insolublepolyesters can be dis-persed in water up to 20 %

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Concept for submicron fibers by suspensionelectrospinning

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Solution of template polymer

Electrospinning

Removal of template polymer

Template polymer Latex particle

Water

Stoiljkovic et al., Polymer 2007, 48, 3974Stoiljkovic et al., Macromolecules 2009, 42, 6147J. Sun et al., Macromol. Chem. Rapid Commun. 2010, 31, 2077P. Bansal et al., in prep.

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Electrospinning of up-concentrated

secondary dispersions

+ 3 % PEOElectrospinning

Fiber diameter300 – 500 nm

J. Sun, K. Bubel, F. Chen, T. Kissel, S. Agarwal, A. Greiner,Macromol. Chem. Rapid Commun., 2010

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As-spun After water treatment for 2 days

Slight reduction of fiber diameterNo Brij78 and PEO left

Polyester+PEO+Brij78No suspension particles visible

Water treatment of electrospun fibers of secondarydispersions

Water-stable electrospun biodegradable fibersfrom aqueous secondary dispersions

Water-stable electrospun biodegradable fibersfrom aqueous secondary dispersions

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How about the biodegradability

0 20 40 60 80 1000

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40

60

80

100

Wei

ghtl

oss(

%)

Time of degradation(h)

with enzyme (Pseudomonas lipase)

without enzyme

Fast enzymatic degradation

Slow hydrolytic degradation

Low cytoxicity (without tenside)

F. ChenY. Zhang

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Take home message

Electrospinning of secondarydispersions of alipahatic poly-esters results in water stablebiodegradable nanofibernonwovens

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Nanofiber nonwovensPheromone releasingMicrocapsules???

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Water dispersed phermone filled microcapsules

Requirements for microcapsules

- Uptake of large amount of hydrophobic pheromone

- Microcapsules should be biodegradable

- Microcapsules should allow release of pheromone

- Microcapsules of should be well dispersable in water

The pheromone

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Water dispersed phermone filled microcapsules

The hypothesisOligolactides with hydroxy/carboxylateend groups will fullfill all requirementsfor water dispersion and biodegradability

The answer: It is wrong

HOO

O

O

O-K+

n

OLA

New hypothesisPheromone will act as hydrohob and thereby stabilize dispersions

The answer: It is right

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The observationStable dispersions OLA with pheromoneNo stable dispersions of OLA alone

OLA/pheromone/BrijS2010 / 10 / 1 % P. Bansal

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Take home message

Dispersions of OLA are onlyStable up to 10 % withpheromone as stabilizer!!!

Without pheromone

With pheromone

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How to measure dispenser efficiency on field?

Nonwoven with pheromone

Cage with lonely female beatle–how many male will visit here?Ass less as better for us – Quantification!

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Pheromone release is not yet retarted enough

Our serendiptywill continue

Take home messageBiodegradable polyester nanoparticle dispersions up tp 20 %Biodegradable water stable polyester nanofibers from waterHigh solid content OLA microcapsules dispersion with pheromones

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Support: University of Marburg, DFG, BMBF, BLE, BASF

The teams: Agarwal and Greiner group

We do not risk because it is difficult - It is difficult because we do not riskSeneca

Partners - Profs: S. Agarwal, J. H. Wendorff, G. Leithold

Poster D-PO4-27: Thermo- and photoresponsive Nanomats by Electrospinning…..(Agarwal / Brandl) – today afternoon only!!!