Drug delivery from the biopolyester poly(3-hydroxybutyrate ...
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Drug delivery from the biopolyester poly(3-hydroxybutyrate- co-3-hydroxyvalerate)
Transcript of Drug delivery from the biopolyester poly(3-hydroxybutyrate ...
Drug delivery from the biopolyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
Table of contents
• Introduction
• What are PHAs?
• Potential of PHAs in biomedical applications
• Why to work with PHAs?
• What are the advantages to use PHAs instead of other existing
polymers?
• Why to encapsulate a drug?
• Method used for PHBV encapsulation
• Results
• Conclusions
• Questions
Introduction What are PHAs?
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Introduction
Potential of PHAs in biomedical applications
Type of applications Products
Wound managementSutures, skin substitutes, surgical meshes, swabs
Vascular system Heart valves, pericardial patches, vascular grafts
Orthopaedy
Scaffolds for cartilage engineering, spinal cages, bone graft substitutes,meniscus regeneration, internal fixation devices (e.g., screws)
Urology Urological stent
Dental Barrier material for guided tissue regeneration periodontitis
Computer assisted tomography and ultrasound imaging
Contrast agents
M. Zinn et al., Advanced Drug Delivery Reviews, 2001
Introduction
Why to use PHA as matrix
material?
• Polymer degradation controls the release rate
of drugs
• Can be degraded by ester bond hydrolysis
• By acid or basic hydrolysis
• By water
• By non-specific enzymes (lipases &
esterases) present in the human body
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Introduction Why to use PHA and not PLGA?
• PLGA is the polymer most commonly used in this field
• Its degradation provokes local inflammation due to acidic monomer release
Chemical structure of PLGA
• PHAs do not provoke any inflammatory response during hydrolysis
• PHBV and PHB are the polyhydroxyalkanoates that are most commonly used for encapsulation processes
• P4HB was the first PHA approved by FDA
Different chemical structures of PHAs
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Introduction Why to select poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV?
• Produced by bacterial fermentation using Ralstoniaeutropha
• It is a random copolymer composed of [R]-3-hydroxybutyrate and [R]- 3-hydroxyvalerate
• This polymer is known to be highly crystalline and have a high melting point
• PHBV is a well defined polymer used for drug delivery system:
• Antibiotics release • Hormones release • Anti-cancers release O O O
O OCH3
CH3
m n
3-hydroxybutyrate 3-hydroxyvalerate
IntroductionWhy to encapsulate a drug?
• Help the active compound to reach the zone of
action
• Protect the active compound and increase its
stability
• Control the release rate
• Increase life quality of patients
• To target a specific organ or a type of cells
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Introduction Why controlled drug release system?
• In order to control the release rate and the duration of the activity of an API in the body
• Permit to optimize existing treatmentsDecreasing the side effect : e.g., chemotherapy treatment Avoid overdoses of the drug compound
• Increase the life quality of the patient More effective treatment Decrease of the frequency of medication
Introduction Crucial factors to take in count for a controlled drug release system
• Type of drug
• Drug loading
• Composition of the polymer
• Drug-polymer Interaction
• Bead size distributionFigure 5: Different release rate, (I) exponential release rate,
(II) constant release rate giving a zero order kinetics, (III)
zero kinetics with a time delay, (IV) pulsatile release with
delay, (V) multiple release with constant delay in between.
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A.K. Bajpai, Progess in polymer science,2008
Methods
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• The microspheres are harvested by centrifugation at
10’000xg for 10 minutes at RT
• Supernatant discard and the pellet washed in distilled
water
• The pellet is resuspended and stirred at 40 rpm for 30
min at 40 °C
• The operation is done twice • The washed pellet was dried under vacuum at RT and
stored under the same condition until further uses
• Encapsulation by solvent evaporation
– Most commonly used methods.
• Principle : mainly 4 steps
1. Emulsion
2. Evaporation
3. Harvesting
4. Drying
MethodsEmulsion solvent evaporation process
• PHA is dissolved in a water immiscible solvent
• The drug is dissolved in this solution
• Solution is added dropwise in a solution of 1% (wt/v)
of polyvinyl alcohol
• The solution are emulsified by stirring (9’000 rpm)
• The emulsified solution was gentle stirred overnight at
50°C for solvent evaporation
• The droplets are solidified
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Results Optimization of microspheres
production
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ResultsSet up the best “encapsulation” conditions
• Optimization of the polymer solution concentration
• 0.1% (wt/v)
• 1% (wt/v)
• 5% (wt/v)
• 10% (wt/v)
• Study of the emulsion time
• 7 minutes
• 15 minutes
• Drying steps evaluation
• Freeze-drying
• Vacuum oven at RT
• Evaluation of two evaporation techniques
• Evaporation at RT and at 50°C
• Evaluation of two emulsion techniques
• High speed homogenizer
• Magnetic stirring
• Drop formation study
• Manual drops formation
• Drop formation using a syringe pump
• Syringe pump + Nisco nozzle
• Syringe pump + Nisco nozzle and air
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ResultsDifferent PHBV concentrations
10% (wt/v)Size distribution: ND
5% (wt/v)Size distribution: 0.4-9 µm
1% (wt/v)Size distribution: 0.3-4.5 µm
0.1% (wt/v)Size distribution: 0.7-11.8 µm
10 µm
10 µm 10 µm
10 µm
Best concentrations: 1 and 5 % (wt/v)
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ResultsEmulsion time study
Experiment done with PHBV 5%Using high speed homogenizer at 9’000 rpm
7 minutesSize distribution: 0.7-6.5 µm
15 minutesSize distribution: 0.7-5.5 µm
No significant differences using two emulsion times (at least in this range)
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ResultsDrying step evaluation
Lyophilisation PHBV 5%
PHBV 1%
Vacuum dryPHBV 5%
PHBV 1%
10 µm
2 µm
10 µm10 µm
2 µm 10 µm
2 µm10 µm• Arrangement due to the lyophilisation technique • Lyophilisation did not provoke merging of microspheres • Merging due to the dichloromethane diffusion out of the beads
10 µm
10 µm
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ResultsEvaluation of two evaporation temperatures
10 µm
Evaporation at RT Evaporation at 50°C
PHBV 1%
10 µm
PHBV 5%
No beads merged at 50°C, the dichloromethane was efficiently removed from the beads at elevated temperature
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ResultsDifferent emulsion techniques
Magnetic agitation was not enough powerful to form small droplets:
• Too high viscosity of the solution
• Magnetic stirring has lower shear forces than the high speed homogenizer
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ResultsMaterials used to study the drop formation
Syringe pump used for reproducible drop formation Flow rate 2 ml∙min-1
Nisco nozzle Nisco nozzle connected to a glass syringe
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ResultsInfluence of the drop formation on microspheres
10 µm10 µm
10 µm 10 µm
Syringe + Nisco and airSyringe + Nisco
Syringe pumpManual
Size distribution:0.6 to 6.5 µm
Size distribution:Not determined
Size distribution:0.8 to 5.8 µm
Size distribution:0.4 to 8 µm
• The drop formation under the selected conditions influences only
little the bead formation
• The spraying was not well adjusted: the solvent evaporated too fast
defaulting the drop formation 21
ResultsSummary of the best conditions for the encapsulation of PHBV
Parameters Conditions
Drop formation Syringe pump at 2 mL∙min-1
Polymer concentration 5% (wt/v)
Emulsion technique High speed homogenizer at 9’000 rpm
Evaporation techniqueEvaporation under stirring at 50°C
overnight
Drying technique Vacuum oven at RT
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Results Loading and encapsulation efficiency
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ResultsNifedipine encapsulation at different concentrations with PHBV
10 µm
10 µm
10 µm
10 µm
A
10 µm
NFD 20% (wt/wt)
NFD 5% (wt/wt)NFD 10%
(wt/wt)
NFD 15% (wt/wt)
• The Nifedipine concentration at 20% was too high and some crystals were visible outside of the microspheres, no crystals visible for the others concentrations
• The size distribution and the bead’s shape were not affected by the Nifedipine encapsulation
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ResultsDetermination of the NFD loaded with PHBV
35.1927.80 27.92
94.71
50
100
150
200
0
50
100
150
200
250
PHBV NFD 5% PHBV NFD 10% PHBV NFD 15% PHBV NFD 20%
Nif
ed
ipin
e (
µg)
The mass of polymer was kept constant for each encapsulation: 100 mgThe loading analysis was performed with 1 mg of loaded microspheres
Polymer encapsulation capacity was around 30 µg of NFD for 1 mg of polymer ( 3%)
Loading efficiency:70%
Loading efficiency:28%
Loading efficiency:19%
Loading efficiency:47%
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ResultsDrug release studies
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ResultsMicrospheres used and characteristics for the release study
10 µm
Microspheres loaded with 5% of NFD
10 µm
Microspheres loaded with 10% of NFD
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ResultsDrug release study from PHBV
• The release study was done during 90 h in PBS (pH 7.4) at 37°C stirred at 150 rpm
• The weight of microsphere loaded was calculated in order to be in the solubility range
(5.9 µg∙mL-1 in water at 25°C) and in the calibration range (0 to 10 µg∙mL-1 )
0.000
0.200
0.400
0.600
0.800
1.000
0 20 40 60 80 100
Cu
mu
lati
ve N
FD r
elea
se (
µg/
µg)
PHBV 5%_1 PHBV 5%_2
0.000
0.200
0.400
0.600
0.800
1.000
0 10 20 30 40 50 60 70 80
PHBV 10%_1 PHBV 10%_2Release duration (h)
• For both loadings a burst effect takes place during the first 3 hours to reach 10% of drug release
• 5% of NFD loading: 40% of the API was released after 30 hours into the media
• 10% of NFD loading: 40% of the API was released after 30 h but continued to increase to 52 %
• The release for both NFD concentrations seems to be caused by drug diffusion
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5% loading 10% loading
Conclusions
• Emulsion solvent evaporation is multifactor dependent
• Emulsion solvent evaporation technique permit to encapsulate an hydrophobic
compound
• The drug loading does not affect the release rate
• The Nifedipine release was first due to the drug diffusion
• The drug loading does not affect the microsphere’s size distribution
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Questions
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Nifidipine encapsulation with PHAs having different physical properties
ResultsNifedipine encapsulation at different concentrations with PHA C1150
• The Nifedipine at 20% was to high as for the PHBV some crystals are visible outside of the beads
• The other concentrations no crystals were visible• No Nifedipine was found loaded with these polymers
• In this study two polymer were used, • PHA with 43 mol% (PHA C1143) of vinyl and 52 mol% (PHA C1152)
• For both polymers a concentration of 5% was used
PHA C1152 NFD 5 %
10 µm10 µm
PHA C1152 NFD 10 %PHA C1143 NFD 20 %
10 µm
Size distribution : 3 to 8 µm Size distribution : 2.6 to 13 µm Size distribution : 2.6 to 13 µm
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ResultsNifedipine encapsulation at different concentrations with PHA C12
10 µm
NFD 5 % (wt/wt) NFD 10 % (wt/wt)
10 µm 10 µm
NFD 15 % (wt/wt)
Size distribution: 0.3 to 4 µm Size distribution: 1 to 10 µm Size distribution: not determined
• PHA C12 loaded with 5% present smooth surface and the beads size smaller than the
PHA C12 loaded with 10% of NFD
• The PHA C12 was emulsionned 12 minutes instead of 7 min. in order to encapsulate
more polymer
• The surface PHA C12 10% NDF present small “holes” on the surface and the size
distribution was higher
• No Nifedipine was found loaded
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