Development of biomaterials that provide mechanical and molecular cues for wound healing and rege... more Development of biomaterials that provide mechanical and molecular cues for wound healing and regeneration must meet several design parameters. In addition to high biocompatibility, biomaterials should possess suitable porosity as well as the ability to be chemically tailored to control parameters including biodegradability and bioactivity. These characteristics were studied in hyaluronan (HA), a natural polymer found in the body. HA
... Brandon L. Seal and Alyssa Panitch*. Harrington Department of Bioengineering, Arizona State U... more ... Brandon L. Seal and Alyssa Panitch*. Harrington Department of Bioengineering, Arizona State University, PO Box 879709, Tempe, Arizona 85287-9709. Macromolecules , 2006, 39 (6), pp 22682274. DOI: 10.1021/ma0524528. ...
The pressure and temperature dependence of the cloud point transition of an aqueous solution of a... more The pressure and temperature dependence of the cloud point transition of an aqueous solution of an elastin-like polypeptide (MGLDGSMG(VPGIG)40VPLE), prepared by bacterial expression of the corresponding artificial gene, was measured. A temperature-pressure diagram was constructed over a wide range of conditions. The (VPGIG)40 solution exhibited a well-defined pressure-induced cloudpoint (Pc), as well as a temperature-induced transition (Tc). From near atmospheric pressure up to 100 MPa, Tc increased with increasing pressure, but decreased with further increases in pressure above 200 MPa. The maximum Tc was reached at 100-200 MPa. Between 10 and 25 degrees C, the Pc decreased with increasing temperature, and a broad maximum in Pc was observed in the range -10 to 0 degree C. These results are compared with our previous results on synthetic thermoresponsive vinyl polymers.
A rapidly forming polymer matrix with affinity-based controlled release properties was developed ... more A rapidly forming polymer matrix with affinity-based controlled release properties was developed based upon interactions between heparin-binding peptides and heparin. Dynamic mechanical testing of 10% (w/v) compositions consisting of a 3:1 molar ratio of poly(ethylene glycol)-co-peptide (approximately 18,000 g/mol) to heparin (approximately 18,000 g/mol) revealed a viscoelastic profile similar to that of concentrated, large molecular weight polymer solutions and melts. In addition, the biopolymer mixtures recovered quickly following thermal denaturation and mechanical insult. These gel-like materials were able to sequester exogenous heparin-binding peptides and could release these peptides over several days at rates dependent on relative heparin affinity. The initial release rates ranged from 3.3% per hour for a peptide with low heparin affinity to 0.025% per hour for a peptide with strong heparin affinity. By altering the affinity of peptides to heparin, a series of peptides can be developed to yield a range of release profiles useful for controlled in vivo delivery of therapeutics.
Journal of tissue engineering and regenerative medicine, 2015
Non-specific cytotoxins, including paclitaxel and sirolimus analogues, currently utilized as anti... more Non-specific cytotoxins, including paclitaxel and sirolimus analogues, currently utilized as anti-restenotic therapeutics, affect not only smooth muscle cells (SMCs) but also neighbouring vascular endothelial cells (ECs). These drugs inhibit the formation of an intact endothelium following vessel injury, thus emphasizing the critical need for new candidate therapeutics. Utilizing our in vitro models, including EC monolayers and both hyperplastic and quiescent EC-SMC co-cultures, we investigated the ability of DS-SILY20 , a decorin mimic, to promote EC health. DS-SILY20 increased EC proliferation and migration by 1.5- and 2-fold, respectively, which corresponded to increased phosphorylation of ERK-1/2. Interestingly, IL-6 secretion and the production of both E-selectin and P-selectin were reduced in the presence of 10 μ m DS-SILY20 , even in the presence of the potent pro-inflammatory cytokine platelet-derived growth factor (PDGF). In hyperplastic and quiescent EC-SMC co-cultures, DS...
Dunkin Hartley guinea pigs, a commonly used animal model of osteoarthritis, were used to determin... more Dunkin Hartley guinea pigs, a commonly used animal model of osteoarthritis, were used to determine if high frequency ultrasound can ensure intra-articular injections are accurately positioned in the knee joint. A high-resolution small animal ultrasound system with a 40 MHz transducer was used for image-guided injections. A total of 36 guinea pigs were anaesthetised with isoflurane and placed on a heated stage. Sterile needles were inserted directly into the knee joint medially, while the transducer was placed on the lateral surface, allowing the femur, tibia and fat pad to be visualised in the images. B-mode cine loops were acquired during 100 µl. We assessed our ability to visualise 1) important anatomical landmarks, 2) the needle and 3) anatomical changes due to the injection. From the ultrasound images, we were able to visualise clearly the movement of anatomical landmarks in 75% of the injections. The majority of these showed separation of the fat pad (67.1%), suggesting the inj...
Vitreous liquefaction and subsequent posterior vitreous detachment can lead to several sight-thre... more Vitreous liquefaction and subsequent posterior vitreous detachment can lead to several sight-threatening diseases, including retinal detachment, macular hole and macular traction syndrome, nuclear cataracts, and possibly, open-angle glaucoma. In this study, we tested the ability of three novel synthetic chondroitin sulfate proteoglycan mimics to preserve the structure and physical properties of enzymatically-degraded bovine vitreous. Chondroitin sulfate proteoglycan mimics, designed to bind to type II collagen, hyaluronic acid, or both, were applied to trypsin- or collagenase-treated bovine vitreous in situ and in vitro. Rheology and liquefaction tests were performed to determine the physical properties of the vitreous, while Western blots were used to detect the presence and degradation of soluble collagen II (α1). Deep-etch electron microscopy (DEEM) identified the ultrastructure of mimic-treated and untreated enzyme-degraded bovine vitreous. Proteoglycan mimics preserved the phys...
Failure of neural recording electrodes implanted in the brain is often attributed to the formatio... more Failure of neural recording electrodes implanted in the brain is often attributed to the formation of glial scars around the implant. A leading cause of scar formation is the electrode material. Described below is an approach to evaluate the biocompatibility of novel electrode materials in a representative three-dimensional model. The model, brain slice culture, accounts for the response of the neural tissue in the absence of the systemic response. While limitations of any in vitro model exist, brain slice culture provides an indication of the response of neurons and glia in an environment more indicative of the in vivo environment than two-dimensional cell culture of glia or neurons alone. Polybenzylcyclobutene (BCB) electrodes were developed as test materials for flexible electrodes due to ease of processing, low water uptake, and inherent flexibility when formed in thin sheets. Biocompatibilty of the BCB neural electrodes was evaluated using living brain slices derived from the hippocampal regions of 100 g CD rats. Importantly, fewer animals can be used in brain slice culture to evaluate the neural tissue response than when using live animals, since several slices can be obtained per animal. Cellular response to the electrodes was evaluated at 0, 7, and 14 days. At all time points living cells, both neurons and glia, were observed in the vicinity of the electrode. In addition, cells were observed migrating out from the brain slices onto the shank of the BCB electrode. Brain slice culture is shown to be a viable alternative to in vivo evaluation, in that the response of both neurons and glia can be evaluated in a native three-dimensional state, while sacrificing fewer animals. Future in vivo evaluation with BCB will provide definitive answers on the degree of glial scarring in response to this new and biocompatible electrode material.
This work describes a unique system of gel and gel-like materials formed from physical bonds betw... more This work describes a unique system of gel and gel-like materials formed from physical bonds between heparin and heparin binding peptides (dG-PBD) coupled to multivalent poly(ethylene glycol) vinyl sulfone star polymers (PEGVS) and formed from covalent bonds between an enzymatically sensitive crosslinker and PEGVS. Dynamic mechanical testing revealed that the viscoelastic behavior and gelation kinetics of 10% (w/v) gels formed from 2:1 dG-PBD:PEGVS, heparin, and crosslinker (2:1 gels) and from 3:1 dG-PBD:PEGVS, heparin, and crosslinker (3:1 materials) were significantly influenced by the presence of both physical and covalent bonds. Furthermore, the mechanical properties of both compositions were thermally responsive and reversible. At 4 degrees C, the storage modulus, G', for 2:1 gels (5005.3+/-592.0Pa) and 3:1 materials (5512.0+/-272.7Pa) were statistically similar; however, at 45 degrees C, G' of 2:1 gels decreased to 477.9+/-150.4Pa, and the viscoelastic behavior of 3:1 materials was dominated by viscous behavior. In addition, the mechanical properties of 2:1 gels and 3:1 materials were sensitive to the frequency of the applied stress at 4 degrees C, 20 degrees C, and at 37 degrees C. Although the covalent bonds within the materials provided mechanical stability, the overall viscoelastic response of this system could be dominated by physical crosslinks under certain conditions. Results from degradation studies indicated that the crosslinker was sensitive to collagenase type I but not to thrombin or heparinase I, and a hemolysis assay suggested that the 2:1 gels and 3:1 materials might be biocompatible. These materials could be useful to study the role of physical interactions within networks that mimic the extracellular matrix.
Pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and Interleukin 6 (IL-6) are mediators... more Pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and Interleukin 6 (IL-6) are mediators in the development of many inflammatory diseases. To demonstrate that macrophages take up and respond to thermosensitive nanoparticle drug carriers we synthesized PEGylated poly(N-isopropylacrylamide-2-acrylamido-2-methyl-1-propanesulfonate) particles cross-linked with degradable disulfide (N,N'-bis(acryloyl)cystamine) (NGPEGSS). An anti-inflammatory peptide (KAFAK) was loaded and released from the thermosensitive nanoparticles and shown to suppress levels of TNF-α and IL-6 production in monocytes. Cellular uptake of fluorescent thermosensitive degradable nanoparticles and therapeutic efficacy of free KAFAK peptide compared to KAFAK loaded in PEGylated degradable thermosensitive nanoparticles was examined. The data suggests that the degradable, thermosensitive nanoparticles loaded with KAFAK may be an effective tool to treat inflammatory diseases.
Development of biomaterials that provide mechanical and molecular cues for wound healing and rege... more Development of biomaterials that provide mechanical and molecular cues for wound healing and regeneration must meet several design parameters. In addition to high biocompatibility, biomaterials should possess suitable porosity as well as the ability to be chemically tailored to control parameters including biodegradability and bioactivity. These characteristics were studied in hyaluronan (HA), a natural polymer found in the body. HA
... Brandon L. Seal and Alyssa Panitch*. Harrington Department of Bioengineering, Arizona State U... more ... Brandon L. Seal and Alyssa Panitch*. Harrington Department of Bioengineering, Arizona State University, PO Box 879709, Tempe, Arizona 85287-9709. Macromolecules , 2006, 39 (6), pp 22682274. DOI: 10.1021/ma0524528. ...
The pressure and temperature dependence of the cloud point transition of an aqueous solution of a... more The pressure and temperature dependence of the cloud point transition of an aqueous solution of an elastin-like polypeptide (MGLDGSMG(VPGIG)40VPLE), prepared by bacterial expression of the corresponding artificial gene, was measured. A temperature-pressure diagram was constructed over a wide range of conditions. The (VPGIG)40 solution exhibited a well-defined pressure-induced cloudpoint (Pc), as well as a temperature-induced transition (Tc). From near atmospheric pressure up to 100 MPa, Tc increased with increasing pressure, but decreased with further increases in pressure above 200 MPa. The maximum Tc was reached at 100-200 MPa. Between 10 and 25 degrees C, the Pc decreased with increasing temperature, and a broad maximum in Pc was observed in the range -10 to 0 degree C. These results are compared with our previous results on synthetic thermoresponsive vinyl polymers.
A rapidly forming polymer matrix with affinity-based controlled release properties was developed ... more A rapidly forming polymer matrix with affinity-based controlled release properties was developed based upon interactions between heparin-binding peptides and heparin. Dynamic mechanical testing of 10% (w/v) compositions consisting of a 3:1 molar ratio of poly(ethylene glycol)-co-peptide (approximately 18,000 g/mol) to heparin (approximately 18,000 g/mol) revealed a viscoelastic profile similar to that of concentrated, large molecular weight polymer solutions and melts. In addition, the biopolymer mixtures recovered quickly following thermal denaturation and mechanical insult. These gel-like materials were able to sequester exogenous heparin-binding peptides and could release these peptides over several days at rates dependent on relative heparin affinity. The initial release rates ranged from 3.3% per hour for a peptide with low heparin affinity to 0.025% per hour for a peptide with strong heparin affinity. By altering the affinity of peptides to heparin, a series of peptides can be developed to yield a range of release profiles useful for controlled in vivo delivery of therapeutics.
Journal of tissue engineering and regenerative medicine, 2015
Non-specific cytotoxins, including paclitaxel and sirolimus analogues, currently utilized as anti... more Non-specific cytotoxins, including paclitaxel and sirolimus analogues, currently utilized as anti-restenotic therapeutics, affect not only smooth muscle cells (SMCs) but also neighbouring vascular endothelial cells (ECs). These drugs inhibit the formation of an intact endothelium following vessel injury, thus emphasizing the critical need for new candidate therapeutics. Utilizing our in vitro models, including EC monolayers and both hyperplastic and quiescent EC-SMC co-cultures, we investigated the ability of DS-SILY20 , a decorin mimic, to promote EC health. DS-SILY20 increased EC proliferation and migration by 1.5- and 2-fold, respectively, which corresponded to increased phosphorylation of ERK-1/2. Interestingly, IL-6 secretion and the production of both E-selectin and P-selectin were reduced in the presence of 10 μ m DS-SILY20 , even in the presence of the potent pro-inflammatory cytokine platelet-derived growth factor (PDGF). In hyperplastic and quiescent EC-SMC co-cultures, DS...
Dunkin Hartley guinea pigs, a commonly used animal model of osteoarthritis, were used to determin... more Dunkin Hartley guinea pigs, a commonly used animal model of osteoarthritis, were used to determine if high frequency ultrasound can ensure intra-articular injections are accurately positioned in the knee joint. A high-resolution small animal ultrasound system with a 40 MHz transducer was used for image-guided injections. A total of 36 guinea pigs were anaesthetised with isoflurane and placed on a heated stage. Sterile needles were inserted directly into the knee joint medially, while the transducer was placed on the lateral surface, allowing the femur, tibia and fat pad to be visualised in the images. B-mode cine loops were acquired during 100 µl. We assessed our ability to visualise 1) important anatomical landmarks, 2) the needle and 3) anatomical changes due to the injection. From the ultrasound images, we were able to visualise clearly the movement of anatomical landmarks in 75% of the injections. The majority of these showed separation of the fat pad (67.1%), suggesting the inj...
Vitreous liquefaction and subsequent posterior vitreous detachment can lead to several sight-thre... more Vitreous liquefaction and subsequent posterior vitreous detachment can lead to several sight-threatening diseases, including retinal detachment, macular hole and macular traction syndrome, nuclear cataracts, and possibly, open-angle glaucoma. In this study, we tested the ability of three novel synthetic chondroitin sulfate proteoglycan mimics to preserve the structure and physical properties of enzymatically-degraded bovine vitreous. Chondroitin sulfate proteoglycan mimics, designed to bind to type II collagen, hyaluronic acid, or both, were applied to trypsin- or collagenase-treated bovine vitreous in situ and in vitro. Rheology and liquefaction tests were performed to determine the physical properties of the vitreous, while Western blots were used to detect the presence and degradation of soluble collagen II (α1). Deep-etch electron microscopy (DEEM) identified the ultrastructure of mimic-treated and untreated enzyme-degraded bovine vitreous. Proteoglycan mimics preserved the phys...
Failure of neural recording electrodes implanted in the brain is often attributed to the formatio... more Failure of neural recording electrodes implanted in the brain is often attributed to the formation of glial scars around the implant. A leading cause of scar formation is the electrode material. Described below is an approach to evaluate the biocompatibility of novel electrode materials in a representative three-dimensional model. The model, brain slice culture, accounts for the response of the neural tissue in the absence of the systemic response. While limitations of any in vitro model exist, brain slice culture provides an indication of the response of neurons and glia in an environment more indicative of the in vivo environment than two-dimensional cell culture of glia or neurons alone. Polybenzylcyclobutene (BCB) electrodes were developed as test materials for flexible electrodes due to ease of processing, low water uptake, and inherent flexibility when formed in thin sheets. Biocompatibilty of the BCB neural electrodes was evaluated using living brain slices derived from the hippocampal regions of 100 g CD rats. Importantly, fewer animals can be used in brain slice culture to evaluate the neural tissue response than when using live animals, since several slices can be obtained per animal. Cellular response to the electrodes was evaluated at 0, 7, and 14 days. At all time points living cells, both neurons and glia, were observed in the vicinity of the electrode. In addition, cells were observed migrating out from the brain slices onto the shank of the BCB electrode. Brain slice culture is shown to be a viable alternative to in vivo evaluation, in that the response of both neurons and glia can be evaluated in a native three-dimensional state, while sacrificing fewer animals. Future in vivo evaluation with BCB will provide definitive answers on the degree of glial scarring in response to this new and biocompatible electrode material.
This work describes a unique system of gel and gel-like materials formed from physical bonds betw... more This work describes a unique system of gel and gel-like materials formed from physical bonds between heparin and heparin binding peptides (dG-PBD) coupled to multivalent poly(ethylene glycol) vinyl sulfone star polymers (PEGVS) and formed from covalent bonds between an enzymatically sensitive crosslinker and PEGVS. Dynamic mechanical testing revealed that the viscoelastic behavior and gelation kinetics of 10% (w/v) gels formed from 2:1 dG-PBD:PEGVS, heparin, and crosslinker (2:1 gels) and from 3:1 dG-PBD:PEGVS, heparin, and crosslinker (3:1 materials) were significantly influenced by the presence of both physical and covalent bonds. Furthermore, the mechanical properties of both compositions were thermally responsive and reversible. At 4 degrees C, the storage modulus, G', for 2:1 gels (5005.3+/-592.0Pa) and 3:1 materials (5512.0+/-272.7Pa) were statistically similar; however, at 45 degrees C, G' of 2:1 gels decreased to 477.9+/-150.4Pa, and the viscoelastic behavior of 3:1 materials was dominated by viscous behavior. In addition, the mechanical properties of 2:1 gels and 3:1 materials were sensitive to the frequency of the applied stress at 4 degrees C, 20 degrees C, and at 37 degrees C. Although the covalent bonds within the materials provided mechanical stability, the overall viscoelastic response of this system could be dominated by physical crosslinks under certain conditions. Results from degradation studies indicated that the crosslinker was sensitive to collagenase type I but not to thrombin or heparinase I, and a hemolysis assay suggested that the 2:1 gels and 3:1 materials might be biocompatible. These materials could be useful to study the role of physical interactions within networks that mimic the extracellular matrix.
Pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and Interleukin 6 (IL-6) are mediators... more Pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and Interleukin 6 (IL-6) are mediators in the development of many inflammatory diseases. To demonstrate that macrophages take up and respond to thermosensitive nanoparticle drug carriers we synthesized PEGylated poly(N-isopropylacrylamide-2-acrylamido-2-methyl-1-propanesulfonate) particles cross-linked with degradable disulfide (N,N'-bis(acryloyl)cystamine) (NGPEGSS). An anti-inflammatory peptide (KAFAK) was loaded and released from the thermosensitive nanoparticles and shown to suppress levels of TNF-α and IL-6 production in monocytes. Cellular uptake of fluorescent thermosensitive degradable nanoparticles and therapeutic efficacy of free KAFAK peptide compared to KAFAK loaded in PEGylated degradable thermosensitive nanoparticles was examined. The data suggests that the degradable, thermosensitive nanoparticles loaded with KAFAK may be an effective tool to treat inflammatory diseases.
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Papers by Alyssa Panitch