Monthly Archives: August 2013

Recent article about 3D printing of PLLA and PLGA

Recent article relates use of 3d printing for generating scaffolds of PLLA and PLGA.

—abstract—

Biodegradable porous scaffolds have been investigated as an alternative approach to current metal, ceramic, and polymer bone graft substitutes for lost or damaged bone tissues. Although there have been many studies investigating the effects of scaffold architecture on bone formation, many of these scaffolds were fabricated using conventional methods such as salt leaching and phase separation, and were constructed without designed architecture. To study the effects of both designed architecture and material on bone formation, this study designed and fabricated three types of porous scaffold architecture from two biodegradable materials, poly (L-lactic acid) (PLLA) and 50:50 Poly(lactic-co-glycolic acid) (PLGA), using image based design and indirect solid freeform fabrication techniques, seeded them with bone morphogenetic protein-7 transduced human gingival fibroblasts, and implanted them subcutaneously into mice for 4 and 8 weeks. Micro-computed tomography data confirmed that the fabricated porous scaffolds replicated the designed architectures. Histological analysis revealed that the 50:50 PLGA scaffolds degraded but did not maintain their architecture after 4 weeks implantation. However, PLLA scaffolds maintained their architecture at both time points and showed improved bone ingrowth, which followed the internal architecture of the scaffolds. Mechanical properties of both PLLA and 50:50 PLGA scaffolds decreased but PLLA scaffolds maintained greater mechanical properties than 50:50 PLGA after implantation. The increase of mineralized tissue helped support the mechanical properties of bone tissue and scaffold constructs between 4–8 weeks. The results indicate the importance of choice of scaffold materials and computationally designed scaffolds to control tissue formation and mechanical properties for desired bone tissue regeneration

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Saito, Eiji, Elly E. Liao, Wei‐Wen Hu, Paul H. Krebsbach, and Scott J. Hollister. “Effects of designed PLLA and 50: 50 PLGA scaffold architectures on bone formation in vivo.” Journal of tissue engineering and regenerative medicine 7, no. 2 (2013): 99-111.

3D printing with Polycaprolactone

Recent research has optimized the parameters for 3D printing with polycaprolactone. In this research synthesized PCL with a molecular weight near 79 kDa (similar to PolyVivo  productAP11) was printed successfully using a Bioscaffolder (Envisiontec GmbH, Gladbeck, Germany) by extruding the molten polymer through a 23Ga heated nozzle at 110C and strands were applied onto a collector plate in a layer-by-layer method at a speed of 350mm/min.  The strand pattern was rotated at 90° angles in between layers which created square pores. The distance between strands was 0.9 mm with a spindle speed of 200 rpm.  The resultant elastic modulus of PCL is ~59MPa but the modulus (compressive) of the scaffold was around 10MPa. Note the density of crystalline and the amorphous PCL is 1.200 and 1.021 g/cm3, respectively.

Capture

Seyednejad, Hajar, Debby Gawlitta, Wouter JA Dhert, Cornelus F. van Nostrum, Tina Vermonden, and Wim E. Hennink. “Preparation and Characterization of a 3D-printed Scaffold Based on a Functionalized Polyester for Bone Tissue Engineering Application.” Functionalized Polyesters 7, no. 5 (2012): 87.

For more details or Check out full-text here http://igitur-archive.library.uu.nl/phar/2012-0222-200652/Seyednejad.pdf#page=87

PolySciTech link organization and assorted info

Below is a listing of links to various technical sites, publications, whitepapers, and other parts of PolySciTech. Often we have customers who are unaware of the various resources we provide across a range of fields.  Browse through the listings below to find out more about different aspects of PST you may be interested in:

Tech help sites

Learn more about polymer degradation kinetics and what controls degradation rates at www.polyscitech.com techsite www.lazypolymer.com

Learn more about making micelles and nanoparticles at www.polyscitech.com techsite http://polymermicelles.com/

Learn more about folate targeting at www.polyscitech.com techsite http://intelligentpolymer.com/

Learn more about PLGA-PEG Maleimide usage and active targeting at www.polyscitech.com techsite http://uncommonpolymer.com/

Learn more about reverse-thermogelation at www.polyscitech.com techsite http://thermogels.com/

Learn more about Poly(Poloxamer 407)-co-hexamethylene-di-isocyanate copolymer methoxy poly(ethylene glycol) at www.polyscitech.com techsite http://weirdpolymer.com/index.php

Learn more about Poly(styrene)-block-Poly(4-vinyl pyridine) at www.polyscitech.com techsite http://weirdpolymer.com/Polystyrene-block-Poly-4-vinyl%20pyridine.php

Learn more about Poly(styrene)-b-poly(DL lactide) at www.polyscitech.com techsite http://weirdpolymer.com/Polystyrene-b-poly-DL%20lactide.php

Learn more about Gelatin Methacrylate at www.polyscitech.com techsite http://weirdpolymer.com/Gelatin-Methacrylate.php

Learn more about common polyesters such as PLGA, PLA, PCL, and PLCL at www.polyscitech.com techsite http://normalpolymer.com/

Whitepapers

Check out www.polyscitech.com technical whitepaper for a wide variety of watersoluble block copolymers and their capacity to dissolve a poorly soluble drug-model here http://akinainc.com/pdf/Whitepaper-micelle%20solubilization.pdf

Check out www.polyscitech.com technical whitepaper regarding a dual-sensitive (pH and temperature) polymer here http://www.akinainc.com/pdf/AO14-pH-Temperature-sensitive.pdf

Check out www.polyscitech.com thermogel users manual here http://www.akinainc.com/pdf/PolyVivo%20AK12-AK24%20thermogelation.pdf

Check out www.polyscitech.com nanoparticle/micelle whitepaper with mPEG-PCL here http://www.akinainc.com/pdf/Whitepaper-PolyVivo-AK01-liposomes.pdf

Publications

Check out Ge et. al. 2012 article on use of www.polyscitech.com PLGA-PEG-PLGA (Polyvivo AK12) to inject electrically responsive nanoparticles full-text here http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3489921/

Check out Rapoport et. al. 2013 article on use of www.polyscitech.com mPEG-PLA (Polyvivo AK09) to deliver PTX to pancreatic cancer model in conjunction with ultrasound techniques full-text here http://www.jtultrasound.com/content/pdf/2050-5736-1-11.pdf

Check out Thakkar et. al. 2013 article on use of www.polyscitech.com mPEG-PLA (PolyVivo AK09) to improve vascular permeation in conjunction with ultrasound techniques here http://www.sciencedirect.com/science/article/pii/S0301562913006868

Check out Liu et. al. 2013 article on use of www.polyscitech.com PLGA-PEG-PLGA (Polyvivo AK24) to deliver cidofovir via the intratympianic route here http://informahealthcare.com/doi/abs/10.3109/03639045.2013.789054

Check out Gullioti et. al. 2013 article on use of www.polyscitech.com mPEG-PLGA (Polyvivo AK30) for nanoparticle-tumor delivery of PTX here http://link.springer.com/article/10.1007/s11095-013-1039-y

Check out Ebbesen et. al. 2013 article on use of www.polyscitech.com mPEG-PLGA (Polyvivo AK10) for pegylated nanoparticle formulation development here http://link.springer.com/article/10.1007/s11095-013-1018-3

Check out Grabowski et. al. 2013 article on use of www.polyscitech.com PLGA-Rhodamine B conjugate (PolyVivo AV11) for tracking nanoparticles here http://www.sciencedirect.com/science/article/pii/S0378517313004286

Sites

Find Polyscitech Block copolymers including PEG-PLGA, PEG-PLA, PEG-PCL and others here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#BlockCopolymers

Find PolyScitech reactive intermediates for further customization including PLGA-NH2, PLGA-PEG-NHS, PLGA-PEG-Maleimide, PLA-diacrylate and others here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#Intermediates

Find PolySciTech specially modified poly(ethylene glycol)/Poly(ethylene oxide) such as folate, fluorescent, and reactive endcapped PEGs here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#PEGs

Find PolySciTech monomers such as lactide, glycolide, choline-acrylate, and others here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#Monomers

Even a product range as broad as PolySciTech has a miscellaneous category, here you find poly(NIPAM) derivatives, PCL-PEI, gelatin-methacrylate, and others here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#Others

Find PolySciTech specialty polyesters such as 3-arm star PLA, PLGA-glucose, Poly(caprolactone-co-dioxanone) and others here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#SpecialtyPolyesters

Find PolySciTech linear polyesters such as PLA, PCL, PLGA and others here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#Polyesters

Find PolySciTech fluorescently encapped polymers such as PLGA-FITC, PLGA-Rhodamine, and near-IR labeled PLGA here https://akinainc.com/polyscitech/products/polyvivo/sequential.php#PolymerVisualization

Find PolySciTech superporous hydrogel technology platform here https://akinainc.com/polyscitech/products/aquagel/

Find DKC BioActs Flamma Fluor fluorescent dyes distributed in USA by PolySciTech here https://akinainc.com/polyscitech/products/flammafluor/

Find PolySciTech specialty Chitosan (Kitopure) here https://akinainc.com/polyscitech/products/Kitopure/

Find PolySciTech imaging systems and laboratory equipment here https://akinainc.com/polyscitech/products/lab-equipment/

Find Akina device for scale-up generation of homogenous microparticles here http://www.spinswiper.com/

Did you know that PolySciTech offers sample analysis? For a full listing of analysis capabilities check out our page here https://akinainc.com/polyscitech/contractResearch/Sample-Analysis/

 

PolyVivo AK09 nanodroplet delivery

Recent publication from Thakker et. al. further describes the combination of ultrasound and nanodroplet therapy utilizing PolyVivo AK09 as the emulsifying agent. This was done by directly dissolving the water soluble AK09 5% w/v in saline and sonicating with 1% perfluoro-15-crown-5-ether to emulsify the fluorocarbon. It was noted that the emulsion was stable in the refrigerator for several weeks indicating a highly stable emulsion.

 

Thakkar, Dhaval, Roohi Gupta, Kenneth Monson, and Natalya Rapoport. “Effect of Ultrasound on the Permeability of Vascular Wall to Nano-emulsion Droplets.” Ultrasound in medicine & biology (2013). (http://www.sciencedirect.com/science/article/pii/S0301562913006868)

—abstract—

The effect of ultrasound on the permeability of blood vessels to nano-emulsion droplets was investigated using excised mouse carotid arteries as model blood vessels. Perfluorocarbon nano-droplets were formed by perfluoro-15-crown-5-ether and stabilized by poly(ethylene oxide)-co-poly(DL-lactide) block co-polymer shells. Nano-droplet fluorescence was imparted by interaction with fluorescein isothiocyanate-dextran (molecular weight = 70,000 Da). The permeability of carotid arteries to nano-droplets was studied in the presence and absence of continuous wave or pulsed therapeutic 1-MHz ultrasound. The data indicated that the application of ultrasound resulted in permeabilization of the vascular wall to nano-droplets. The effect of continuous wave ultrasound was substantially stronger than that of pulsed ultrasound of the same total energy. No effect of blood vessel pre-treatment with ultrasound was observed.

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Use of FPR648 for tracking PTX nanoparticles

A recent article published in Pharmaceutical Research relates the usage of FPR648 to track uptake in-vivo of nanoparticles into tumor cells.  Full text available here (http://www.uic.edu/labs/bpslab/PDF/PharmRes_x_y_2013.pdf)

Image from:

Hollis, Christin P., et al. “In Vivo Investigation of Hybrid Paclitaxel Nanocrystals with Dual Fluorescent Probes for Cancer Theranostics.” Pharmaceutical research (2013): 1-10.

—abstract—-

To develop novel hybrid paclitaxel (PTX) nanocrystals, in which bioactivatable (MMPSense® 750 FAST) and near infrared (Flamma Fluor® FPR-648) fluorophores are physically incorporated, and to evaluate their anticancer efficacy and diagnostic properties in breast cancer xenograft murine model. The pure and hybrid paclitaxel nanocrystals were prepared by an anti-solvent method, and their physical properties were characterized. The tumor volume change and body weight change were evaluated to assess the treatment efficacy and toxicity. Bioimaging of treated mice was obtained non-invasively in vivo.The released MMPSense molecules from the hybrid nanocrystals were activated by matrix metalloproteinases (MMPs) in vivo, similarly to the free MMPSense, demonstrating its ability to monitor cancer progression. Concurrently, the entrapped FPR-648 was imaged at a different wavelength. Furthermore, when administered at 20 mg/kg, the nanocrystal formulations exerted comparable efficacy as Taxol®, but with decreased toxicity. Hybrid nanocrystals that physically integrated two fluorophores were successfully prepared from solution. Hybrid nanocrystals were shown not only exerting antitumor activity, but also demonstrating the potential of multi-modular bioimaging for diagnostics.

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Thermogel FAQ

often get quite a few questions on thermogels. A few answers to common ones below:

 

FAQ: AK12, AK24, AK36, AK48? What are these and what can you tell me about them?

A- “AK12: PLGA-PEG-PLGA (Mn ~1000-1000-1000, 1:1 LA:GA) – this one is the quickest degrading thermogel we have because it is very short and 50:50 LA:GA (which is quick degrading). This one was used in a publication by Zare’s group out at Stanford (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3489921/) for injecting and holding microparticles.

 

AK24 PLGA-PEG-PLGA (Mn ~1100-1000-1100, 3:1 LA:GA)  – just a little slower degrading than the AK12 but similar thermogelling properties. Recently published (http://informahealthcare.com/doi/abs/10.3109/03639045.2013.789054) for use for cidofovir delivery.  They actually show decent controlled (almost linear after the burst) release for 100hrs with this one (attached image) (they call it “commercial PEG-PLGA-PEG”, they also synthesized another one with higher MW as well).  Although this is a small-molecule, it is highly water soluble (170mg/ml, drugbank) so such a controlled release is still fairly impressive.

AK36: mPEG-PCL (Mw 750-2500) – This one is a little unique, very slow degrading and a little tricky to dissolve requiring initially 4C followed by 0.5hr at 80C to break up crystalline domains.  This one is suggested for only long-term (several months) delivery.

 

Additionally there is AK46 (PLA-PEG-PLA 1000-1000-1000) which is also a thermogel. It is similar to AK12/AK24 in gelation but pure lactide so more stable.  AK36 and AK46 are fairly new so there aren’t any publications out with them yet.”

FAQ: The polyscitech website suggests a solution at 4°C is stable for 2-3 weeks.  Is the gelled form of the solution more stable than the cold aqueous solution?

A- “This is from our users guide (http://www.akinainc.com/pdf/PolyVivo%20AK12-AK24%20thermogelation.pdf) and what is meant by the polymer solution “being stable” in this case is before some degradation has occurred that could change the properties in terms of gelation and longevity in the body (if already partially degraded, may not last as long in testing).  We have noticed AK12/AK24 solutions left in the fridge over a month or two have gelled spontaneously, but the exact timeline on this has not been determined. In a practical sense its best to use solutions fairly soon.  By no means are these more stable heated in gel state than in cold state just simply due to temperature.  Stability for these is just due to hydrolytic degradation so water will start to break-down the chains when in contact but this process is slower at lower temperatures. We provide these as dry solids (which is their most stable form) and I suggest storing them dry and reconstituting close to time of use in water.”

AV06 and FPI749 usage in-vivo imaging

I often get questions about the use of FPI749 as well as conjugates such as AV06 and here’s some helpful info on these.

 

FAQ: Is the dye stable enough to use in-vivo?

“Our experience has been the dye is extremely stable and usable in-vivo. It was used previously by Dr. Li’s group at University of Kentucky to track PTX nanoparticles (full-text articles at http://tigger.uic.edu/labs/bpslab/PDF/MolPharmaceutics_8_1985_2011.pdf and http://www.uic.edu/labs/bpslab/PDF/PharmRes_x_y_2013.pdf for similar FPR648). Additionally we uses the AV06 conjugate here to make 50um PLGA microparticles which we injected SubQ and IM in a mouse model and tracked for up to 22 days until euthanasia (results not published but images shown at bottom of website here https://akinainc.com/polyscitech/products/imaging/elvis.php). ”

 

FAQ: What’s the detection limit/Best ratio for imaging?

“It depends on quantity of material, depth of tissue, and quality of imager.  FPR749 has a quantum yield of 0.04 but it operates in a very long-wave near-infrared region so there is limited noise from other sources. In Dr. Li’s research he used 0.79% w/w FPR749/PTX and was able to track in rat model to specific organs/tumors in an IVIS system.  In our research we utilized the ELVIS system which has less depth of permeation than an IVIS system.  We used 100% AV06 to make the microparticles for this one and were able to track but this was only SubQ/IM so only a depth of 5-10mm or so.

Hydrophobic Polyesters

Due to popular demand PolySciTech has begun marketing hydrophobic polyesters which encourage surface eroding profiles rather than bulk degradation which typifies traditional polyesters like PLGA (for a detailed explanation of bulk vs. surface eroding see an excellent review article Uhrich et. al. 1999 full text here). To encourage surface erosion emphasis is placed on hydrophobicity so as to discourage water permeation into the matrix for the following polymers.

 Cat: AP96 Name: Poly(caprolactone)-cholesterol endcap polymer (Mn: 25,000-35,000 Da)

PCL is fairly hydrophobic to begin with but the addition of bulky, hydrophobic cholesterol endcap further discourages water permeation.  Dissolves easily in organic solvents such as dichloromethane for processability.

 

Cat: AO36 Name: Poly(butylene-succinate-co-L-lactide) (Mn 5000-10,000) (PBSLA)

(nominal mass ratio succinate:butylene:lactide: 54:26:20)

Poly(butylene succinate) PBS is already known to be primarily surface eroding
(http://www.plaza1.snu.ac.kr/~fpbk21/master/subject/Download/Seoul_20060829190827.pdf)
and has been shown to have biocompatibility (http://beyotime.com/reference/c0038-ref7.pdf) however processing is limited due to solubility problems. AO36 is a random copolymer of the succinate/butylene along with lactide so as to render the polymer matrix as a whole soluble in DCM while still retaining the hydrophobicity of the PBS.