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Zhang Q, Meyerhoff ME. Nitric Oxide Release for Enhanced Biocompatibility and Analytical Performance of Implantable Electrochemical Sensors. ELECTROANAL 2021. [DOI: 10.1002/elan.202100174] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Qi Zhang
- Department of Chemistry University of Michigan Ann Arbor MI 48109 USA
| | - Mark E. Meyerhoff
- Department of Chemistry University of Michigan Ann Arbor MI 48109 USA
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2
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Bhave G, Chen JC, Singer A, Sharma A, Robinson JT. Distributed sensor and actuator networks for closed-loop bioelectronic medicine. MATERIALS TODAY (KIDLINGTON, ENGLAND) 2021; 46:125-135. [PMID: 34366697 PMCID: PMC8336425 DOI: 10.1016/j.mattod.2020.12.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Designing implantable bioelectronic systems that continuously monitor physiological functions and simultaneously provide personalized therapeutic solutions for patients remains a persistent challenge across many applications ranging from neural systems to bioelectronic organs. Closed-loop systems typically consist of three functional blocks, namely, sensors, signal processors and actuators. An effective system, that can provide the necessary therapeutics, tailored to individual physiological factors requires a distributed network of sensors and actuators. While significant progress has been made, closed-loop systems still face many challenges before they can truly be considered as long-term solutions for many diseases. In this review, we consider three important criteria where materials play a critical role to enable implantable closed-loop systems: Specificity, Biocompatibility and Connectivity. We look at the progress made in each of these fields with respect to a specific application and outline the challenges in creating bioelectronic technologies for the future.
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3
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Yum K, McNicholas TP, Mu B, Strano MS. Single-walled carbon nanotube-based near-infrared optical glucose sensors toward in vivo continuous glucose monitoring. J Diabetes Sci Technol 2013; 7:72-87. [PMID: 23439162 PMCID: PMC3692218 DOI: 10.1177/193229681300700109] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This article reviews research efforts on developing single-walled carbon nanotube (SWNT)-based near-infrared (NIR) optical glucose sensors toward long-term in vivo continuous glucose monitoring (CGM). We first discuss the unique optical properties of SWNTs and compare SWNTs with traditional organic and nanoparticle fluorophores regarding in vivo glucose-sensing applications. We then present our development of SWNT-based glucose sensors that use glucose-binding proteins and boronic acids as a high-affinity molecular receptor for glucose and transduce binding events on the receptors to modulate SWNT fluorescence. Finally, we discuss opportunities and challenges in translating the emerging technology of SWNT-based NIR optical glucose sensors into in vivo CGM for practical clinical use.
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Affiliation(s)
- Kyungsuk Yum
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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4
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Abstract
Continuous glucose monitoring devices remain limited in their duration of use due to difficulties presented by the foreign body response (FBR), which impairs sensor functionality immediately following implantation via biofouling and leukocyte infiltration. The FBR persists through the life of the implant, culminating with fibrous encapsulation and isolation from normal tissue. These issues have led researchers to develop strategies to mitigate the FBR and improve tissue integration. Studies have often focused on abating the FBR using various outer coatings, thereby changing the chemical or physical characteristics of the sensor surface. While such strategies have led to some success, they have failed to fully integrate the sensor into surrounding tissue. To further address biocompatibility, researchers have designed coatings capable of actively releasing biological agents (e.g., vascular endothelial growth factor, dexamethasone, and nitric oxide) to direct the FBR to induce tissue integration. Active release approaches have proven promising and, when combined with biocompatible coating materials, may ultimately improve the in vivo lifetime of subcutaneous glucose biosensors. This article focuses on strategies currently under development for mitigating the FBR.
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Affiliation(s)
- Ahyeon Koh
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Ju YM, Yu B, West L, Moussy Y, Moussy F. A dexamethasone-loaded PLGA microspheres/collagen scaffold composite for implantable glucose sensors. J Biomed Mater Res A 2010; 93:200-10. [PMID: 19536830 DOI: 10.1002/jbm.a.32512] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We have developed a new dexamethasone (Dex)-loaded poly(lactic-co-glycolic acid) microspheres/porous collagen scaffold composite for implantable glucose sensors. The scaffolds were fabricated around the sensing element of the sensors and crosslinked using nordihydroguaiaretic acid (NDGA). The microspheres containing Dex were incorporated into the NDGA-crosslinked collagen scaffold by dipping in microsphere suspension in either water or Pluronic. The loading efficiencies of Dex in the microspheres and the scaffold were determined using high performance liquid chromatography. The microspheres/scaffold composite fabricated using microspheres in the hydrogel solution had a better loading efficiency than when microspheres were in water suspension. The composite fabricated using the hydrogel also showed a slower and more sustained drug release than the standard microspheres in vitro during a 4 week study and did not significantly affect the function of the sensors in vitro. The sensors with the composite that were still functional retained above 50% of their original sensitivity at 2 weeks. Histology showed that the inflammatory response to the Dex-loaded composite was much lower than for the control scaffold at 2 and 4 weeks after implantation. The Dex-loaded composite system might be useful to reduce inflammation to implanted glucose sensors and therefore extend their function and lifetime.
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Affiliation(s)
- Young Min Ju
- Department of Chemical & Biomedical Engineering, University of South Florida, Tampa, FL 33620-5350, USA
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6
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Ju YM, Yu B, West L, Moussy Y, Moussy F. A novel porous collagen scaffold around an implantable biosensor for improving biocompatibility. II. Long-term in vitro/in vivo sensitivity characteristics of sensors with NDGA- or GA-crosslinked collagen scaffolds. J Biomed Mater Res A 2010; 92:650-8. [PMID: 19235209 DOI: 10.1002/jbm.a.32400] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have developed a new 3D porous and biostable collagen scaffold for implantable glucose sensors. The scaffolds were fabricated around the sensors and crosslinked using nordihydroguaiaretic acid (NDGA) or glutaraldehyde (GA) to enhance physical and biological stability. The effect of the scaffolds on sensor function and biocompatibility was examined during long-term (>or=28 days) in vitro and in vivo experiments and compared with control bare sensors. To evaluate the effect of the sensor length on micromotion and sensor function, we also fabricated short and long sensors. 3D porous scaffold application around glucose sensors did not significantly affect the long-term in vitro sensitivity of the sensors. The scaffolds, crosslinked by either NDGA or GA, remained stable around the sensors during the 4 week in vitro study. In the long-term in vivo study, the sensitivity of the short sensors was higher than the sensitivity of long sensors presumably because of less micromotion in the subcutis of the rats. The sensors with NDGA-crosslinked scaffolds had a higher sensitivity than the sensors with GA-crosslinked scaffolds. Histological examination showed that NDGA-crosslinked scaffolds retained their physical structure with reduced inflammation when compared with the GA-crosslinked scaffolds. Therefore, the application of NDGA-crosslinked collagen scaffolds might be a good method for enhancing the function and lifetime of implantable biosensors by minimizing the in vivo foreign body response.
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Affiliation(s)
- Young Min Ju
- Biomedical Engineering Program, University of South Florida, 4202 E. Fowler Avenue, ENB 118, Tampa, Florida 33620-5350, USA
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7
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Abstract
This article reviews current efforts to make glucose sensors based on the inherent optical properties of single walled carbon nanotubes. The advantages of single walled carbon nanotubes over traditional organic and nanoparticle fluorophores for in vivo-sensing applications are discussed. Two recent glucose sensors made by our group are described, with the first being an enzyme-based glucose sensor that couples a reaction mediator, which quenches nanotube fluorescence, on the surface of the nanotube with the reaction of the enzyme. The second sensor is based on competitive equilibrium binding between dextran-coated nanotubes and concanavalin A. The biocompatibility of a model sensor is examined using the chicken embryo chorioallantoic membrane as a tissue model. The advantages of measuring glucose concentration directly, like most optical sensors, versus measuring the flux in glucose concentration, like most electrochemical sensors, is discussed.
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Affiliation(s)
- Paul W Barone
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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8
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Sung J, Barone PW, Kong H, Strano MS. Sequential delivery of dexamethasone and VEGF to control local tissue response for carbon nanotube fluorescence based micro-capillary implantable sensors. Biomaterials 2009; 30:622-31. [DOI: 10.1016/j.biomaterials.2008.09.052] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Accepted: 09/23/2008] [Indexed: 11/16/2022]
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Onuki Y, Bhardwaj U, Papadimitrakopoulos F, Burgess DJ. A review of the biocompatibility of implantable devices: current challenges to overcome foreign body response. J Diabetes Sci Technol 2008; 2:1003-15. [PMID: 19885290 PMCID: PMC2769826 DOI: 10.1177/193229680800200610] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In recent years, a variety of devices (drug-eluting stents, artificial organs, biosensors, catheters, scaffolds for tissue engineering, heart valves, etc.) have been developed for implantation into patients. However, when such devices are implanted into the body, the body can react to these in a number of different ways. These reactions can result in an unexpected risk for patients. Therefore, it is important to assess and optimize the biocompatibility of implantable devices. To date, numerous strategies have been investigated to overcome body reactions induced by the implantation of devices. This review focuses on the foreign body response and the approaches that have been taken to overcome this. The biological response following device implantation and the methods for biocompatibility evaluation are summarized. Then the risks of implantable devices and the challenges to overcome these problems are introduced. Specifically, the challenges used to overcome the functional loss of glucose sensors, restenosis after stent implantation, and calcification induced by implantable devices are discussed.
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Affiliation(s)
- Yoshinori Onuki
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut
| | - Upkar Bhardwaj
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut
| | | | - Diane J. Burgess
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut
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Butt OI, Carruth R, Kutala VK, Kuppusamy P, Moldovan NI. Stimulation of peri-implant vascularization with bone marrow-derived progenitor cells: monitoring by in vivo EPR oximetry. ACTA ACUST UNITED AC 2007; 13:2053-61. [PMID: 17518714 DOI: 10.1089/ten.2006.0225] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The poorly vascularized fibrous capsule that develops around implantable biomedical devices (for drug delivery, biosensors, etc.) severely limits their applications. We tested the hypotheses that co-implantation of bone marrow-derived progenitor cells could stimulate the vascularization of implants. To assess the presence of functional peri-implant microvasculature, we developed a novel model of implanted device containing an oxygen (O(2))-sensing spin probe (detectable using electron paramagnetic resonance) placed inside a nanoporous filter-limited capsule. These devices were implanted subcutaneously in C57/Bl6 mice alone, with the addition of a Matrigel plug in front of the filter, or with the addition of Matrigel containing equal proportions of c-kit(+) and stem cell antigen-1(+) bone marrow-derived cells. Implants partial pressure of O(2) (pO(2)) were recorded non-invasively and periodically for up to 10 weeks. Tissue surrounding the implants was collected for immunohistochemistry. Initially, there were no differences in pO(2) between the experimental groups. After 3 weeks, the devices supplied with progenitor cells showed more than twice the O(2) concentrations as controls. This difference remained significant for 4 more weeks and then started to decrease slightly, still being 6 mmHg higher than in the controls at 10 weeks post-implantation. Collagen deposition was detected around the control implants, along with F4/80-positive macrophages and giant cells. In the plugs collected from the cell treatment group, we found an active process of adipogenesis, accompanied by neovascularization, and a highly vascularized adipose layer surrounding the implants. In conclusion, we successfully developed a cell therapy-type strategy to maintain vascularization around implanted devices using co-administration of bone marrow-derived progenitor cells, and we demonstrated a novel O(2)-sensing method to functionally monitor neovascularization in vivo.
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Affiliation(s)
- Omar I Butt
- Davis Heart and Lung Research Institute, Department of Internal Medicine/Cardiology, Ohio State University, Columbus, Ohio, USA
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11
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Norton L, Koschwanez H, Wisniewski N, Klitzman B, Reichert W. Vascular endothelial growth factor and dexamethasone release from nonfouling sensor coatings affect the foreign body response. J Biomed Mater Res A 2007; 81:858-69. [PMID: 17236219 PMCID: PMC4070388 DOI: 10.1002/jbm.a.31088] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Vascular endothelial growth factor (VEGF) and dexamethasone (DX) release from hydrogel coatings were examined as a means to modify tissue inflammation and induce angiogenesis. Antibiofouling hydrogels for implantable glucose sensor coatings were prepared from 2-hydroxyethyl methacrylate, N-vinyl pyrrolidinone, and polyethylene glycol. Microdialysis sampling was used to test the effect of the hydrogel coating on glucose recovery. VEGF-releasing hydrogel-coated fibers increased vascularity and inflammation in the surrounding tissue after 2 weeks of implantation compared to hydrogel-coated fibers. DX-releasing hydrogel-coated fibers reduced inflammation compared to hydrogel-coated fibers and had reduced capsule vascularity compared to VEGF-releasing hydrogel-coated fibers. Hydrogels that released both VEGF and DX simultaneously also showed reduced inflammation at 2 weeks implantation; however, no enhanced vessel formation was observed indicating that the DX diminished the VEGF effect. At 6 weeks, there were no detectable differences between drug-releasing hydrogel-coated fibers and control fibers. From this study, hydrogel drug release affected initial events of the foreign body response with DX inhibiting VEGF, but once the drug depot was exhausted these effects disappeared.
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Affiliation(s)
- L.W. Norton
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - H.E. Koschwanez
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - N.A. Wisniewski
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
| | - B. Klitzman
- Kenan Plastic Surgery Research Labs, Duke University, Durham, North Carolina 27708
| | - W.M. Reichert
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708
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Patil SD, Papadmitrakopoulos F, Burgess DJ. Concurrent delivery of dexamethasone and VEGF for localized inflammation control and angiogenesis. J Control Release 2007; 117:68-79. [PMID: 17169457 DOI: 10.1016/j.jconrel.2006.10.013] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2006] [Revised: 09/21/2006] [Accepted: 10/03/2006] [Indexed: 10/24/2022]
Abstract
Localized elution of corticosteroids has been used in suppressing inflammation and fibrosis associated with implantation and continuous in vivo residence of bio-medical devices. However, these agents also inhibit endogenous growth factors preventing angiogenesis at the local tissue, interface thereby delaying the healing process and negatively impacting device performance. In this work, a combination of dexamethasone and vascular endothelial growth factor (VEGF) was investigated for concurrent localized delivery using PLGA microsphere/PVA hydrogel composites. Pharmacodynamic effects were evaluated by histopathological examination of subcutaneous tissue surrounding implanted composites using a rat model. The hydrogel composites were capable of simultaneously releasing VEGF and dexamethasone with approximately zero order kinetics. Composites were successful in controlling the implant/tissue interface by suppressing inflammation and fibrosis as well as facilitating neo-angiogenesis at a fraction of their typical oral or i.v. bolus doses. Implants containing VEGF showed a significantly higher number of mature blood vessels at the end of the 4 week study irrespective of the presence of dexamethasone. Thus, localized concurrent elution of VEGF and dexamethasone can overcome the anti-angiogenic effects of the corticosteroid and can be used to engineer inflammation-free and well-vascularized tissue in the vicinity of the implant. These PLGA microsphere/PVA hydrogel composites show promise as coatings for implantable bio-medical devices to improve biocompatibility and ensure in vivo performance.
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Affiliation(s)
- Siddhesh D Patil
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, CT 06269, United States
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13
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Klueh U, Liu Z, Cho B, Ouyang T, Feldman B, Henning TP, Kaur M, Kreutzer D. Continuous glucose monitoring in normal mice and mice with prediabetes and diabetes. Diabetes Technol Ther 2006; 8:402-12. [PMID: 16800762 DOI: 10.1089/dia.2006.8.402] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
It is well established that the key to minimizing diabetes-associated complications, in both type 1 and type 2 diabetes, is tight regulation of blood glucose levels. Currently the major approach to regulating blood glucose levels in patients with diabetes relies on external blood glucose monitors. However, poor patient compliance usually results in limited insights into the dynamic range of blood glucose levels (i.e., hyperglycemia vs. hypoglycemia), and inadequate prediction and control of blood glucose levels in these patients. Implantable glucose sensors hold promise for controlling blood glucose levels, but currently these sensors have only limited in vivo life span. Recently we have developed an extremely robust murine model for implantable glucose sensors. In the present study, we have extended this model by developing a complete system for real-time continuous glucose monitoring in normal mice and mice with prediabetes and diabetes (type 1). These studies demonstrated that (1) glucose sensors can be implanted and maintained subcutaneously in the mice; (2) continuous glucose sensor data can be obtained for at least 5 days; and (3) subcutaneous blood glucose sensing paralleled blood glucose levels in normal mice and mice with prediabetes and diabetes. Subcutaneous blood glucose sensing also successfully tracked changes in blood glucose levels induced in the mice with diabetes by administration of oral glucose or insulin. These results mirror the results for subcutaneous blood glucose sensing seen in both normal subjects and patients with diabetes, and therefore validate both our continuous glucose monitoring system in the mouse, and the use of the mouse as a model for implantable glucose sensing in vivo.
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Affiliation(s)
- Ulrike Klueh
- Department of Surgery, Center for Molecular Tissue Engineering, School of Medicine, University of Connecticut, Farmington, 06030, USA.
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Klueh U, Kreutzer DL. Murine model of implantable glucose sensors: a novel model for glucose sensor development. Diabetes Technol Ther 2005; 7:727-37; discussion 738-40. [PMID: 16241876 DOI: 10.1089/dia.2005.7.727] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Although implantable glucose sensors have existed for over 30 years, their function deteriorates in hours to days, in large part as a result of tissue responses to the implanted sensor (i.e., acute and chronic inflammation, fibrosis, and vessel regression). Little is known about the mediators and mechanisms that control these tissue responses to implantable glucose sensors. In the present study, we developed and validated a murine model for implantable glucose sensors, which suitably parallel sensor function in humans. Using special care in implantation and implant retaining techniques, we demonstrated that (1) sensor function deteriorates rapidly within days post-implantation and (2) loss of glucose sensor function correlated with tissue reactions at the sites of sensor implantation, especially in the vicinity of the glucose oxidase-based working electrode. These studies establish a murine model that can be used to evaluate implantable glucose sensors in vivo. This model should provide the foundation for future studies to understand the factors and mechanisms that control sensor function in vivo.
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Affiliation(s)
- Ulrike Klueh
- Center for Molecular Tissue Engineering and Department of Surgery, University of Connecticut School of Medicine, Farmington, Connecticut 06030, USA.
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Norton LW, Tegnell E, Toporek SS, Reichert WM. In vitro characterization of vascular endothelial growth factor and dexamethasone releasing hydrogels for implantable probe coatings. Biomaterials 2005; 26:3285-97. [PMID: 15603824 DOI: 10.1016/j.biomaterials.2004.07.069] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 07/30/2004] [Indexed: 11/23/2022]
Abstract
Anti-fouling hydrogel coatings, copolymers of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidinone, and polyethylene glycol, were investigated for the purpose of improving biosensor biocompatibility. These coatings were modified to incorporate poly(lactide-co-glycolide) (PLGA) microspheres in order to release dexamethasone (DX) and/or vascular endothelial growth factor (VEGF). DX and VEGF release kinetics from microspheres, hydrogels, and microspheres embedded in hydrogels were determined in 2-week and 1-month studies. Overall, monolithic, non-degradable hydrogel drug release had an initial burst followed by release at a significantly lower amount. Microsphere drug release kinetics exhibited an initial burst followed by sustained release for 1 month. Embedding microspheres in hydrogels resulted in attenuated drug delivery. VEGF release from embedded microspheres, 1.1+/-0.3 ng, was negligible compared to release from hydrogels, 197+/-33 ng. After the initial burst from DX-loaded hydrogels, DX release from embedded microspheres was similar to that of hydrogels. The total DX release from hydrogels, 155+/-35 microg, was greater than that of embedded microspheres, 60+/-6 microg. From this study, hydrogel sensor coatings should be prepared incorporating VEGF in the hydrogel and DX either in the hydrogel or in DX microspheres embedded in the hydrogel.
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Affiliation(s)
- L W Norton
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
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Klueh U, Dorsky DI, Kreutzer DL. Enhancement of implantable glucose sensor function in vivo using gene transfer-induced neovascularization. Biomaterials 2005; 26:1155-63. [PMID: 15451635 DOI: 10.1016/j.biomaterials.2004.04.017] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2003] [Accepted: 04/19/2004] [Indexed: 11/22/2022]
Abstract
The in vivo failure of implantable glucose sensors is thought to be largely the result of inflammation and fibrosis-induced vessel regression at sites of sensor implantation. To determine whether increased vessel density at sites of sensor implantation would enhance sensor function, cells genetically engineered to over-express the angiogenic factor (AF) vascular endothelial cell growth factor (VEGF) were incorporated into an ex ova chicken embryo chorioallantoic membrane (CAM)-glucose sensor model. The VEGF-producing cells were delivered to sites of glucose sensor implantation on the CAM using a tissue-interactive fibrin bio-hydrogel as a cell support and activation matrix. This VEGF-cell-fibrin system induced significant neovascularization surrounding the implanted sensor, and significantly enhanced the glucose sensor function in vivo. This model system, for the first time, provides the "proof of principle" that increasing vessel density at the sites of implantation can enhance glucose sensor function in vivo, and demonstrates the potential of gene transfer and tissue interactive fibrin bio-hydrogels in the development of successful implants.
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Affiliation(s)
- Ulrike Klueh
- Center for Molecular Tissue Engineering, University of Connecticut, School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA
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