Category Archives: Polymer Surfaces

PLGA from PolySciTech used as part of biodegradable magnesium-based cardiovascular stent development

PolySciTech division of Akina, Inc. (www.polyscitech.com) provides a wide array of biodegradable polymers including PLGA. Recently PLGA from PolySciTech was used by researchers as a control polymer for development of polymer coated resorbable magnesium stents. Read more: Gu, Xinzhu, Zhongwei Mao, Sang-Ho Ye, Youngmi Koo, Yeoheung Yun, Tiasha Tarannum, Vesselin Shanov, and William R. Wagner. “Biodegradable, Elastomeric Coatings with Controlled Anti-proliferative Agent Release for Magnesium-based Cardiovascular Stents.” Colloids and Surfaces B: Biointerfaces (2016). http://www.sciencedirect.com/science/article/pii/S0927776516302570

“Abstract: Vascular stent design continues to evolve to further improve the efficacy and minimize the risks associated with these devices. Drug-eluting coatings have been widely adopted and, more recently, biodegradable stents have been the focus of extensive evaluation. In this report, biodegradable elastomeric polyurethanes were synthesized and applied as drug-eluting coatings for a relatively new class of degradable vascular stents based on Mg. The dynamic degradation behavior, hemocompatibility and drug release were investigated for poly(carbonate urethane) urea (PCUU) and poly(ester urethane) urea (PEUU) coated magnesium alloy (AZ31) stents. Poly(lactic-co-glycolic acid) (PLGA) coated and bare stents were employed as control groups. The PCUU coating effectively slowed the Mg alloy corrosion in dynamic degradation testing compared to PEUU-coated, PLGA-coated and bare Mg alloy stents. This was confirmed by electron microscopy, energy-dispersive x-ray spectroscopy and magnesium ion release experiments. PCUU-coating of AZ31 was also associated with significantly reduced platelet adhesion in acute blood contact testing. Rat vascular smooth muscle cell (rSMC) proliferation was successfully inhibited when paclitaxel was released from pre-loaded PCUU coatings. The corrosion retardation, low thrombogenicity, drug loading capacity, and high elasticity make PCUU an attractive option for drug eluting coating on biodegradable metallic cardiovascular stents. Keywords: Polymer coating; magnesium stents; drug eluting coating”

PCL-PEG block copolymers investigated for joint repair

PolySciTech Division of Akina, Inc. (www.polyscitech.com) provides a wide array of biodegradable block copolymers for a variety of applications including PCL-PEG block copolymers. Recently PEG-PCL block copolymers were investigated in regards to use as a lubricating surface for artificial knee joints and tested for their ability to withstand simulated ‘walking’ conditions. Read more: Hsu, Chih Yueh, Chin Chung Wei, and Cho Pei Jiang. “Tribological Study of PCL-PEG-PCL Polymer on SiNxHy Base.” In Key Engineering Materials, vol. 642, pp. 264-269. 2015. http://www.scientific.net/KEM.642.264

“Abstract: Tribological behaviour of polymer and hard coating films is complicated with bio-lubricant. Contacting and kinematic conditions of a knee joint when a person in running was simulated in the study. Substrates of specimens are Ti6Al4V and 316LVM stainless steel. Two kinds of polymer films, PCL-PEG-PCL and mPEG-PCL-mPEG, were used to simulate the tissue of cartilage. The silicon nitride film, SiNxHy prepared by PECVD, was used as a protecting film, and it’s thickness about 1000 nm under the polymer film. The testing device was developed, upper specimen is rotated reversely and the lower one is moved linearly forward and backward for 6 mm. A frequency vibration is applied under the lower specimen to simulate the vibration caused from walking, which is sated 2 Hz. Two torque meters are used for friction measurement in rotational and sliding directions. Experiments simulated vertical vibration, rotary and reciprocating motion. Comparing friction coefficient with different substrates with SiNxHy film, mixture of PCL-PEG-PCL and bovine serum can effectively decrease friction but useless for mPEG-PCL-mPEG. If adhesion of PCL-PEG-PCL polymer can be improved, it has potential in the application of artificial joint. Keywords: Friction, Pin on Disc, Polymer, Vertical Vibration”

PLGA from PolySciTech used for investigating blood interactions with metal alloys

PolySciTech (www.polyscitech.com) provides a wide array of biodegradable polymers including PLGA. Recently PLGA from PolySciTech was used for investigation of blood compatibility. Read more: Nguyen, Thanh Yen, Aaron F. Cipriano, Ren‐Guo Guan, Zhan‐Yong Zhao, and Huinan Liu. “In vitro interactions of blood, platelet, and fibroblast with biodegradable magnesium‐zinc‐strontium alloys.” Journal of Biomedical Materials Research Part A (2015). http://onlinelibrary.wiley.com/doi/10.1002/jbm.a.35429/full

“Abstract: Magnesium (Mg) alloy is an attractive class of metallic biomaterial for cardiovascular applications due to its biodegradability and mechanical properties. In this study, we investigated the degradation in blood, thrombogenicity, and cytocompatibility of Magnesium-Zinc-Strontium (Mg-Zn-Sr) alloys, specifically four Mg-4 wt % Zn-xSr (x = 0.15, 0.5, 1, and 1.5 wt %) alloys, together with pure Mg control and relevant reference materials for cardiovascular applications. Human whole blood and platelet rich plasma (PRP) were used as the incubation media to investigate the degradation behavior of the Mg-Zn-Sr alloys. The results showed that the PRP had a greater pH increase and greater concentration of Mg2+ ions when compared with whole blood after 2 h of incubation with the same respective Mg alloys, suggesting that the Mg alloys degraded faster in PRP than in whole blood. The Mg alloy with 4 wt % Zn and 0.15 wt % Sr (named as ZSr41A) was identified as the most promising alloy for cardiovascular stent applications, because it showed slower degradation and less thrombogenicity, as indicated by the lower concentrations of Mg2+ ions released and less deposition of platelets. Additionally, ZSr41 alloys were cytocompatible with fibroblasts in direct exposure culture in which the cells adhered and proliferated around the samples, with no statistical difference in cell adhesion density compared with the blank reference. Future studies on the ZSr41 alloys are necessary to investigate their direct interactions with other important cells in cardiovascular system, such as vascular endothelial cells and smooth muscle cells. Keywords: magnesium-zinc-strontium alloys;biodegradable Mg-Zn-Sr alloys;blood;platelet;fibroblast;in vitro culture;cardiovascular applications”

PolySciTech AP030 PLGA utilized in thesis dissertation on bone scaffolding

PolySciTech (www.polyscitech.com) provides a wide array of PLGA polymer components. Recently PolyVivo AP030 (PLGA 85:15, Mn-10,000-15,000) was utilized to generate porous PLGA/CaSiO3 composite scaffolds which were tested for their potential applications in use for bone scaffolding.  Read more: Qi, Lin. “Porous PLGA-CaSiO3 (Pseudowollastonite) Composite Scaffolds Optimized for Biocompatibility and Osteoinduction.” PhD diss., University of Akron, 2014. Full-Text available: https://etd.ohiolink.edu/!etd.send_file?accession=akron1397041385&disposition=inline

“ABSTRACT: The goal of this study was to develop an optimal porous composite scaffold, composed of pseudowollastonite (psw; β-CaSiO3), and poly(L,D-lactic-co-glycolic acid) (PLGA). In culture medium, the psw released Ca2+ and soluble silica, which are osteoinductive soluble factors. PLGA was utilized as a structural framework and to maintain pH of the scaffold. Scaffolds were prepared by solvent casting/particle leaching technique to obtain porosity and interconnectivity of pores. The mass of NaCl, psw and PLGA were adjusted to determine the effects of the different components on the scaffold’s biocompatibility and osteoinductive potential, in vitro, on two types of cells, hMSC (human Mesenchymal Stem Cells) and MC3T3 (murine osteoblast precursor cells). An orthogonal study was designed for 9 scaffold compositions. Scanning electron microscopy and micro-computed tomography showed that the scaffold pore structure depended on the amount of NaCl used during fabrication. Variable porosity, and hydrolysis of the psw and PLGA components resulted in pH changes and different released soluble silica concentrations. Total DNA analysis from cell culture in growth medium showed that scaffold compositions which resulted in a small pH shift (± 0.5 on Day 3) and low soluble silica concentration (65±3 ppm) were less cytotoxic than scaffolds for which pH changes were large (±1.2 on Day 3) and soluble silica concentrations were high (87±5 ppm). The viability of hMSCs was lower than that of MC3T3 under the same set of conditions. The hMSCs were incubated on each scaffold surface for 28 days in osteogenic induction medium and alkaline phosphatase staining was used as a preliminary estimate of osteoinductivity of scaffolds. Two scaffold compositions, which showed lower cytotoxicity and higher osteoinductivity than the other compositions, were selected for LIVE/DEAD® staining. Better cell morphology and attachment was observed for the scaffold composed of low NaCl, intermediate psw and intermediate PLGA contents, compared to the scaffold of intermediate NaCl, intermediate psw and high PLGA content. Thus, the optimum psw-PLGA scaffold composition was determined for cell attachment, viability and a preliminary estimate of osteoinduction.”

Amine endcapped PLGA/PLA for improved blood compatibility

PolySciTech (www.polyscitech.com) provides a wide array of amine endcapped PLGA’s, PLA’s, and PCL’s.  The effect of amine endcapping is that these polymers can react easily with a variety of chemistries notably carbodiimide/NHS type reactions. Recently this type of polymer and reaction was utilized to attach heparin to PLA surface to improve hemocompatibility. Read more: Sharkawi, Tahmer, Vincent Darcos, and Michel Vert. “Poly (DL‐lactic acid) film surface modification with heparin for improving hemocompatibility of blood contacting bioresorbable devices.” Journal of Biomedical Materials Research Part A 98, no. 1 (2011): 80-87. http://onlinelibrary.wiley.com/doi/10.1002/jbm.a.33099/full

“Abstract: This work describes a simple method to immobilize heparin by covalent bonding to the surface of poly(lactic acid) film with the aim of showing improved hemocompatibility. Carboxyl groups present in heparin molecules were activated by reaction with N-hydroxy-succinimide and allowed to react with free amino groups created at the surface of poly(dl-lactic acid) films by controlled aminolysis. Contact angle measurements and XPS analysis confirmed the binding. Quantification was determined by radioactivity using heparin labeled with tritium. The surface exhibited anti factor Xa activity, thus confirming the presence of bounded heparin that kept some biological activity. Finally platelets adhesion showed less platelet adhesion on heparin modified films as well as preserved morphology. Keywords: poly(lactic acid);surface modification;heparin immobilization;hemocompatibility;platelet adhesion;bioresorbable;cardiovascular medical device”

PolySciTech PLGA used for Magnesium implant coatings

PolySciTech (www.polyscitech.com) provides a wide array of PLGA’s. Recently PolyVivo PLGA MW ~100kDa 50:50 (currently AP089) was used to coat 3D magnesium implants by electrophoretic deposition thus improving their longevity.  Read more: Tian, Qiao Mu, and Hui Nan Liu. “Electrophoretic Deposition and Characterization of Biocomposites on Magnesium for Orthopedic Applications.” In Advanced Materials Research, vol. 922, pp. 761-766. 2014. http://www.scientific.net/AMR.922.761.

“Abstract: The objective of this study is to produce a uniform and consistent nanophase hydroxyapatite (nHA) and poly (lactic-co-glycolic acid) (PLGA) coating on three-dimensional magnesium (Mg) implants using electrophoretic deposition (EPD) process. Mg is biodegradable, mechanically strong, and promising for orthopedic implant and device applications. However, currently available Mg and its alloys degrade too rapidly to meet clinical needs. To control Mg degradation and promote bone ingrowth, nHA/PLGA composite microspheres were synthesized and deposited onto Mg substrates using EPD process. Annealing was applied to improve the coating adhesion. The surface morphology, composition, and coating cross-section were examined using a scanning electron microscope and energy dispersive X-ray spectrometer. The results showed the presence of calcium, phosphorous, carbon, and oxygen peaks, indicating the successful deposition of nHA/PLGA microspheres on Mg. The corrosion resistance of the coated Mg was evaluated using the Tafel test. The results showed that the nHA/PLGA composite coating improved the corrosion resistance of Mg.”

PLA-PEG-PLA for creating anti-fouling surfaces

PolySciTech (www.polyscitech.com) provides a wide array of PLA-PEG-PLA triblock copolymers under the PolyVivo brand-name including AK08 and others.  Recently these polymers have shown promise for generating anti-fouling surfaces when mixed with PLA. Read more here: Shen, Peng, Kai Tu, Chang Yu Yang, Jian Li, and Ru Xu Du. “Preparation of Anti-Fouling Poly (Lactic Acid)(PLA) Hollow Fiber Membranes via Non-Solvent Induced Phase Separation.” Advanced Materials Research 884 (2014): 112-116. http://www.scientific.net/AMR.884-885.112

“Abstract: Anti-fouling PLA hollow fibers were fabricated using synthesized PLA-PEG-PLA copolymer as an additive to improve the hydrophilicity. The tri-block copolymer was prepared by ring-opening polymerization and a hydrophilic copolymer processing good compatibility with PLA molecule was obtained and utilized to fabricate membrane with PLA by NIPS. Elemental analysis showed that PLA-PEG-PLA could stably exist in membranes and endow the membrane with persistent hydrophilic. Thus the contact angle decreased nearly 20o with 5% PLA-PEG-PLA content, resulting in higher water permeability and BSA rejection which indicated the anti-fouling property of PLA membrane was improved.”

PLGA-PEG-Maleimide for crossing BBB

Did you know that PolySciTech also provides several thiol-reactive PLGA/PLA-PEG-Maleimides (AI20, AI40, AI47, AI48, AI49, AI50, AI52, AI53)? These polymers allow for the conjugation of peptides, antibodies, or other ligands so that the surface of the resultant nanoparticle can interface with cell-receptors. These same types of polymers have previously been used to aid the uptake of tempol across the blood-brain-barrier (BBB).  Read more at: Carroll, Richard T., Deepak Bhatia, Werner Geldenhuys, Ruchi Bhatia, Nicholas Miladore, Anupam Bishayee, and Vijaykumar Sutariya. “Brain-targeted delivery of Tempol-loaded nanoparticles for neurological disorders.” Journal of Drug Targeting 18, no. 9 (2010): 665-674. http://informahealthcare.com/doi/abs/10.3109/10611861003639796

“Abstract: Brain-targeted Tempol-loaded poly-(lactide-co-glycolide) (PLGA) nanoparticles (NPs) conjugated with a transferrin antibody (OX 26) were developed using the nanoprecipitation method. These NPs may have utility in treating neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease. Central to these diseases is an increased production of reactive oxygen and nitrogen species which may take part in the development of these conditions. As proof of principle, the NPs were loaded with Tempol, a free radical scavenger that has been shown to be protective against oxidative insults. To enhance the delivery of NPs to the central nervous system (CNS), we conjugated the transferrin receptor antibody covalently to PLGA NPs using the NHS-PEG3500-Maleimide crosslinker. The NPs showed a particle size suitable for blood brain barrier (BBB) permeation (particle size 80–110 nm) and demonstrated a sustained drug release behavior. A high cellular uptake of antibody-conjugated NPs was demonstrated in RG2 rat glioma cells. The ability of the Tempol-loaded NPs to prevent cell death by resveratrol in RG2 cells was determined using the MTT assay. The conjugated NPs containing Tempol were more effective in preventing cell viability by resveratrol when compared with unconjugated NPs or free Tempol in solution. Our findings suggest that transferrin-conjugated NPs containing antioxidants may be useful in the treatment of neurodegenerative diseases.”

mPEG-PCL surface biocompatibility

The study below highlights some of the capabilities of polyethylene glycol block for improving biocompatibility of the polymer. Check out www.polyvivo.com to learn more.(note the below study was not necessarily performed using a PolySciTech product).

“In this study, we prepared diblock copolymers of poly([var epsilon]-caprolactone) (PCL) and poly(ethylene glycol) (PEG) by aluminum alkoxide catalysts. The biological responses to the spin cast surface of different PCL/PEG diblock copolymers were investigated in vitro. Our results showed that surface hydrophilicity improved with the increased PEG segments in diblock copolymers and that bacteria adhesion was inhibited by increased PEG contents. PCL-PEG 23:77 showed nanotopography on the surface. The number of adhered endothelial cells, platelets and monocytes on diblock copolymer surfaces was inhibited in PCL-PEG 77:23 and enhanced in PCL-PEG 23:77. Nevertheless, the platelet and monocyte activation on PCL-PEG 23:77 was reduced. PCL-PEG 23:77 had better cellular response as well as lower degree of platelet and monocyte activation. The current study was the first one to demonstrate that surface nanotopography could influence not only cell adhesion and growth but also platelet and monocyte activation.”

S.-H. Hsu, C.-M. Tang, C.C.C.-C. Lin, Biocompatibility of poly([var epsilon]-caprolactone)/poly(ethylene glycol) diblock copolymers with nanophase separation. Biomaterials 25(25) (2004) 5593-5601. http://www.sciencedirect.com/science/article/B6TWB-4BWCBWW-2/2/d44c205286fb3dafb38030138b147abb