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Klegerman ME, Peng T, Huang SL, Frierson B, Moody MR, Kim H, McPherson DD. Storage Stability of Atheroglitatide, an Echogenic Liposomal Formulation of Pioglitazone Targeted to Advanced Atheroma with a Fibrin-Binding Peptide. Pharmaceutics 2023; 15:2288. [PMID: 37765257 PMCID: PMC10536356 DOI: 10.3390/pharmaceutics15092288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 08/29/2023] [Accepted: 09/04/2023] [Indexed: 09/29/2023] Open
Abstract
We have conducted a stability study of a complex liposomal pharmaceutical product, Atheroglitatide (AGT), stored at three temperatures, 4, 24, and 37 °C, for up to six months. The six parameters measured were functions of liposomal integrity (size and number), drug payload (loading efficiency), targeting peptide integrity (conjugation efficiency and specific avidity), and echogenicity (ultrasound-dependent controlled drug release), which were considered most relevant to the product's intended use. At 4 °C, liposome diameter trended upward, indicative of aggregation, while liposome number per mg lipid and echogenicity trended downward. At 24 °C, peptide conjugation efficiency (CE) and targeting efficiency (TE, specific avidity) trended downward. At 37 °C, CE and drug (pioglitazone) loading efficiency trended downward. At 4 °C, the intended storage temperature, echogenicity, and liposome size reached their practical tolerance limits at 6 months, fixing the product expiration at that point. Arrhenius analysis of targeting peptide CE and drug loading efficiency decay at the higher temperatures indicated complete stability of these characteristics at 4 °C. The results of this study underscore the storage stability challenges presented by complex nanopharmaceutical formulations.
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Affiliation(s)
- Melvin E. Klegerman
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
| | - Tao Peng
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
| | - Shao-Ling Huang
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
| | - Brion Frierson
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
| | - Melanie R. Moody
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
| | - Hyunggun Kim
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
- Department of Biomechatronic Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - David D. McPherson
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (T.P.); (S.-L.H.); (B.F.); (M.R.M.); (D.D.M.)
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Klegerman ME, Moody MR, Huang SL, Peng T, Laing ST, Govindarajan V, Danila D, Tahanan A, Rahbar MH, Vela D, Genstler C, Haworth KJ, Holland CK, McPherson DD, Kee PH. Demonstration of ultrasound-mediated therapeutic delivery of fibrin-targeted pioglitazone-loaded echogenic liposomes into the arterial bed for attenuation of peri-stent restenosis. J Drug Target 2023; 31:109-118. [PMID: 35938912 DOI: 10.1080/1061186x.2022.2110251] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 07/28/2022] [Accepted: 08/01/2022] [Indexed: 01/05/2023]
Abstract
Peri-stent restenosis following stent implantation is a major clinical problem. We have previously demonstrated that ultrasound-facilitated liposomal delivery of pioglitazone (PGN) to the arterial wall attenuated in-stent restenosis. To evaluate ultrasound mediated arterial delivery, in Yucatan miniswine, balloon inflations were performed in the carotid and subclavian arteries to simulate stent implantation and induce fibrin formation. The fibrin-binding peptide, GPRPPGGGC, was conjugated to echogenic liposomes (ELIP) containing dinitrophenyl-L-alanine-labelled pioglitazone (DNP-PGN) for targeting purposes. After pre-treating the arteries with nitroglycerine, fibrin-binding peptide-conjugated PGN-loaded ELIP (PAFb-DNP-PGN-ELIP also termed atheroglitatide) were delivered to the injured arteries via an endovascular catheter with an ultrasound core, either with or without ultrasound application (EKOSTM Endovascular System, Boston Scientific). In arteries treated with atheroglitatide, there was substantial delivery of PGN into the superficial layers (5 µm from the lumen) of the arteries with and without ultrasound, [(1951.17 relative fluorescence units (RFU) vs. 1901.17 RFU; P-value = 0.939)]. With ultrasound activation there was increased penetration of PGN into the deeper arterial layers (up to 35 µm from the lumen) [(13195.25 RFU vs. 7681.00 RFU; P-value = 0.005)]. These pre-clinical data demonstrate ultrasound mediated therapeutic vascular delivery to deeper layers of the injured arterial wall. This model has the potential to reduce peri- stent restenosis.
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Affiliation(s)
- Melvin E Klegerman
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Melanie R Moody
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Shao-Ling Huang
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Tao Peng
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Susan T Laing
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Vijay Govindarajan
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Delia Danila
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Amirali Tahanan
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Clinical and Translational Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Mohammad H Rahbar
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Center for Clinical and Translational Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Deborah Vela
- Cardiovascular Pathology Research Department, Texas Heart Institute, Houston, TX, USA
| | | | - Kevin J Haworth
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA
| | - Christy K Holland
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA
| | - David D McPherson
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Patrick H Kee
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
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Translational initiatives in thrombolytic therapy. Front Med 2017; 11:1-19. [DOI: 10.1007/s11684-017-0497-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 10/10/2016] [Indexed: 01/26/2023]
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Klegerman ME, Naji AK, Haworth KJ, Zou Y, Golunski E, Peng T, Britton GL, Huang SL, Holland CK, McPherson DD. Ultrasound-enhanced bevacizumab release from echogenic liposomes for inhibition of atheroma progression. J Liposome Res 2015; 26:47-56. [PMID: 25865025 DOI: 10.3109/08982104.2015.1029494] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
CONTEXT Bevacizumab (BEV) is a monoclonal antibody to vascular endothelial growth factor (VEGF) that ameliorates atheroma progression by inhibiting neovascularization. OBJECTIVE We aimed to determine whether BEV release from echogenic liposomes (BEV-ELIP) could be enhanced by color Doppler ultrasound (US) and whether the released BEV inhibits VEGF expression by endothelial cells in vitro. MATERIALS AND METHODS BEV-ELIP samples were subjected to 6 MHz color Doppler ultrasound (MI = 0.4) for 5 min. We assessed release of BEV with a direct ELISA and with fluoresceinated BEV (FITC-BEV) loaded into ELIP by the same method. Human umbilical vein endothelial cell (HUVEC) cultures were stimulated to express VEGF by 10 nM phorbol-12-myristate 13-acetate (PMA). Cell-associated VEGF levels were determined using a cell-based ELISA. RESULTS Overall, US caused an additional 100 µg of BEV to be released or exposed per BEV-ELIP aliquot within 60 min BEV-ELIP treated with US inhibited VEGF expression by 90% relative to non-treated controls and by 70% relative to BEV-ELIP without US. Also, US-treated BEV-ELIP inhibited HUVEC proliferation by 64% relative to untreated controls and by 45% relative to BEV-ELIP without US. DISCUSSION AND CONCLUSION We have demonstrated that BEV-ELIP retains its VEGF-binding activity in a liposomal formulation and that clinical Doppler US can significantly increase that activity, both by releasing free BEV and by enhancing the surface exposure of the immunoreactive antibody.
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Affiliation(s)
- Melvin E Klegerman
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - Ali K Naji
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - Kevin J Haworth
- b Department of Internal Medicine, Division of Cardiovascular Diseases , University of Cincinnati , Cincinnati , OH , USA , and.,c Biomedical Engineering Program , University of Cincinnati , Cincinnati , OH , USA
| | - Yuejiao Zou
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - Eva Golunski
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - Tao Peng
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - George L Britton
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - Shao-Ling Huang
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
| | - Christy K Holland
- b Department of Internal Medicine, Division of Cardiovascular Diseases , University of Cincinnati , Cincinnati , OH , USA , and.,c Biomedical Engineering Program , University of Cincinnati , Cincinnati , OH , USA
| | - David D McPherson
- a Department of Internal Medicine, Division of Cardiovascular Medicine , University of Texas Health Science Center at Houston , Houston , TX , USA
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Klegerman ME, Zou Y, Golunski E, Peng T, Huang SL, McPherson DD. Use of thermodynamic coupling between antibody-antigen binding and phospholipid acyl chain phase transition energetics to predict immunoliposome targeting affinity. J Liposome Res 2014; 24:216-22. [PMID: 24597467 DOI: 10.3109/08982104.2014.891230] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Thermodynamic analysis of ligand-target binding has been a useful tool for dissecting the nature of the binding mechanism and, therefore, potentially can provide valuable information regarding the utility of targeted formulations. Based on a consistent coupling of antibody-antigen binding and gel-liquid crystal transition energetics observed for antibody-phosphatidylethanolamine (Ab-PE) conjugates, we hypothesized that the thermodynamic parameters and the affinity for antigen of the Ab-PE conjugates could be effectively predicted once the corresponding information for the unconjugated antibody is determined. This hypothesis has now been tested in nine different antibody-targeted echogenic liposome (ELIP) preparations, where antibody is conjugated to dipalmitoylphosphatidylethanolamine (DPPE) head groups through a thioether linkage. Predictions were satisfactory (affinity not significantly different from the population of values found) in five cases (55.6%), but the affinity of the unconjugated antibody was not significantly different from the population of values found in six cases (66.7%), indicating that the affinities of the conjugated antibody tended not to deviate appreciably from those of the free antibody. While knowledge of the affinities of free antibodies may be sufficient to judge their suitability as targeting agents, thermodynamic analysis may still provide valuable information regarding their usefulness for specific applications.
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Affiliation(s)
- Melvin E Klegerman
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Texas Health Science Center - Houston , Houston, TX , USA
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In vivo volumetric intravascular ultrasound visualization of early/inflammatory arterial atheroma using targeted echogenic immunoliposomes. Invest Radiol 2011; 45:685-91. [PMID: 20733507 DOI: 10.1097/rli.0b013e3181ee5bdd] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES This study aimed to demonstrate three-dimensional (3D) visualization of early/inflammatory arterial atheroma using intravascular ultrasound (IVUS) and targeted echogenic immunoliposomes (ELIP). IVUS can be used as a molecular imaging modality with the use of targeted contrast agents for atheroma detection. Three-dimensional reconstruction of 2-dimensional IVUS images may provide improved atheroma visualization. MATERIALS AND METHODS Atheroma were induced in arteries of Yucatan miniswine (n = 5) by endothelial cell denudation followed by a 4-week high cholesterol diet. The contralateral arteries were left intact and served as controls. Anti-intercellular adhesion molecule-1 (ICAM-1) and generic gammaglobulin (IgG) conjugated ELIP were prepared. Arteries were imaged using IVUS before and after ELIP injection. Images were digitized, manually traced, segmented, and placed in tomographic sequence for 3D visualization. Atheroma brightness enhancement was compared and reported as mean gray scale values. Plaque volume was quantified both from IVUS and histologic images. RESULTS Anti-ICAM-1 ELIP highlighting of the atheroma in all arterial segments was different compared with baseline (P < 0.05). There was no difference in the mean gray scale values with IgG-ELIP. Arterial 3D IVUS images allowed visualization of the entire plaque distribution. The highlighted plaque/atheroma volume with anti-ICAM-1 ELIP was greater than baseline (P < 0.01). CONCLUSION This study demonstrates specific highlighting of early/inflammatory atheroma in vivo using anti-ICAM-1 ELIP. Three-dimensional IVUS reconstruction provides good visualization of plaque distribution in the arterial wall. This novel methodology may help to detect and diagnose pathophysiologic development of all stages of atheroma formation in vivo and quantitate plaque volume for serial and long-term atherosclerotic treatment studies.
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Hitchcock KE, Caudell DN, Sutton JT, Klegerman ME, Vela D, Pyne-Geithman GJ, Abruzzo T, Cyr PEP, Geng YJ, McPherson DD, Holland CK. Ultrasound-enhanced delivery of targeted echogenic liposomes in a novel ex vivo mouse aorta model. J Control Release 2010; 144:288-95. [PMID: 20202474 PMCID: PMC2878875 DOI: 10.1016/j.jconrel.2010.02.030] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 02/16/2010] [Accepted: 02/25/2010] [Indexed: 11/23/2022]
Abstract
The goal of this study was to determine whether targeted, Rhodamine-labeled echogenic liposomes (Rh-ELIP) containing nanobubbles could be delivered to the arterial wall, and whether 1-MHz continuous wave ultrasound would enhance this delivery profile. Aortae excised from apolipoprotein-E-deficient (n=8) and wild-type (n=8) mice were mounted in a pulsatile flow system through which Rh-ELIP were delivered in a stream of bovine serum albumin. Half the aortae from each group were treated with 1-MHz continuous wave ultrasound at 0.49 MPa peak-to-peak pressure, and half underwent sham exposure. Ultrasound parameters were chosen to promote stable cavitation and avoid inertial cavitation. A broadband hydrophone was used to monitor cavitation activity. After treatment, aortic sections were prepared for histology and analyzed by an individual blinded to treatment conditions. Delivery of Rh-ELIP to the vascular endothelium was observed, and sub-endothelial penetration of Rh-ELIP was present in five of five ultrasound-treated aortae and was absent in those not exposed to ultrasound. However, the degree of penetration in the ultrasound-exposed aortae was variable. There was no evidence of ultrasound-mediated tissue damage in any specimen. Ultrasound-enhanced delivery within the arterial wall was demonstrated in this novel model, which allows quantitative evaluation of therapeutic delivery.
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Affiliation(s)
- Kathryn E Hitchcock
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States.
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Herbst SM, Klegerman ME, Kim H, Qi J, Shelat H, Wassler M, Moody MR, Yang CM, Ge X, Zou Y, Kopechek JA, Clubb FJ, Kraemer DC, Huang S, Holland CK, McPherson DD, Geng YJ. Delivery of stem cells to porcine arterial wall with echogenic liposomes conjugated to antibodies against CD34 and intercellular adhesion molecule-1. Mol Pharm 2010; 7:3-11. [PMID: 19719324 DOI: 10.1021/mp900116r] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In atherosclerosis, the loss of vascular stem cells via apoptosis impairs the capacity of the vascular wall to repair or regenerate the tissue damaged by atherogenic factors. Recruitment of exogenous stem cells to the plaque tissue may repopulate vascular cells and help repair the arterial tissue. Ultrasound-enhanced liposomal targeting may provide a feasible method for stem cell delivery into atheroma. Bifunctional echogenic immunoliposomes (BF-ELIP) were generated by covalently coupling two antibodies to liposomes; the first one specific for CD34 antigens on the surface of stem cells and the second directed against the intercellular adhesion molecule-1 (ICAM-1) antigens on the inflammatory endothelium covering atheroma. CD34+ stem cells from adult bone marrow were incubated on the ICAM-1-expressing endothelium of the aorta of swine fed high cholesterol diets, which was preloaded with BF-ELIP. Significantly increased stem cell adherence and penetration were detected in particular in the aortic segments treated with 1 MHz low-amplitude continuous wave ultrasound. Fluorescence and scanning electron microscopy confirmed the presence of BF-ELIP-bound CD34+ cells in the intimal compartment of the atheromatous arterial wall. Ultrasound treatment increased the number of endothelial cell progenitors migrating into the intima. Thus, under ultrasound enhancement, BF-ELIP bound CD34+ stem cells selectively bind to the ICAM-1 expressing endothelium of atherosclerotic lesions.
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Affiliation(s)
- Stephanie M Herbst
- Division of Cardiology, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas, USA
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Kornmann LM, Reesink KD, Reneman RS, Hoeks APG. Critical appraisal of targeted ultrasound contrast agents for molecular imaging in large arteries. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:181-91. [PMID: 20018434 DOI: 10.1016/j.ultrasmedbio.2009.09.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 08/26/2009] [Accepted: 09/21/2009] [Indexed: 05/25/2023]
Abstract
Molecular imaging may provide new insights into the early detection and development of atherosclerosis before first symptoms occur. One of the techniques in use employs noninvasive ultrasound. In the past decade, experimental and clinical validation studies showed that for the microcirculation targeted ultrasound contrast agents, such as echogenic liposomes, microbubbles and perfluorocarbon emulsions, do improve visualization of specific structures. For large arteries, however, successful application is less obvious. In this review, we will address the challenges for molecular imaging of large arteries. We will discuss the problems encountered in the use of targeted ultrasound contrast agents presently available, mainly based on data obtained in flow chambers and animal studies because clinical studies are lacking. We conclude that molecular imaging of activated endothelium in large- and middle-sized arteries by site-specific accumulation of contrast material is still difficult to achieve due to wall shear stress conditions in these vessels.
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Affiliation(s)
- Liselotte M Kornmann
- Department of Biophysics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands
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Ristori S, Di Cola E, Lunghi C, Richichi B, Nativi C. Structural study of liposomes loaded with a GM3 lactone analogue for the targeting of tumor epitopes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2518-25. [DOI: 10.1016/j.bbamem.2009.10.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 09/10/2009] [Accepted: 10/07/2009] [Indexed: 11/16/2022]
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Klegerman ME, Wassler M, Huang SL, Zou Y, Kim H, Shelat HS, Holland CK, Geng YJ, McPherson DD. Liposomal modular complexes for simultaneous targeted delivery of bioactive gases and therapeutics. J Control Release 2009; 142:326-31. [PMID: 19903503 DOI: 10.1016/j.jconrel.2009.10.037] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 10/20/2009] [Accepted: 10/31/2009] [Indexed: 11/26/2022]
Abstract
Intrinsically echogenic liposomes (ELIP) can be adapted to encapsulate nitric oxide to facilitate ultrasound-enhanced delivery of therapeutic agents to atherosclerotic plaques. However, the NO loading of targeted ELIP caused a 93% decrease of antibody (Ab) immunoreactivity. The following hypothesis was tested: biotin/avidin-mediated coupling of NO-ELIP and Ab-conjugated ELIP will enable co-delivery of bioactive gases and ELIP that can encapsulate other agents without loss of targeting efficiency. Complex formation was initiated by addition of excess streptavidin to equal proportions of biotinylated Ab-ELIP and NO-ELIP. Fluorescence deconvolution microscopy, Coulter Multisizer 3 analysis and flow cytometry demonstrated that the ELIP coupling procedure formed mixed aggregates of >or=10 liposomes within 1 min. Intravascular ultrasound imaging and ELISA showed that echogenicity and targeting efficiency were completely and 69-99% retained, respectively. When complexed to NO-ELIP, ELIP bifunctionally targeted to both CD34 and ICAM-1 (BF-ELIP) increased human mononuclear cell migration through human coronary artery endothelial cell monolayers in transwell plates 4-fold relative to a nonspecific IgG-ELIP control and 2-fold relative to BF-ELIP alone. It was concluded that this novel multi-functional conjugation methodology provides a platform technology for site-specific co-delivery of bioactive gases and other agents.
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Affiliation(s)
- Melvin E Klegerman
- Division of Cardiology, Department of Internal Medicine, University of Texas Health Science Center, 6431 Fannin Street, MSB 1.246, Houston, Texas 77030, USA.
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Klegerman ME, Zou Y, McPherson DD. Fibrin targeting of echogenic liposomes with inactivated tissue plasminogen activator. J Liposome Res 2008; 18:95-112. [PMID: 18569446 DOI: 10.1080/08982100802118482] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Fibrin-specific molecular targeting strategies are desirable for site-specific imaging and treatment of late stage atheroma, but fibrin-specific antibodies are difficult to produce and present immunogenicity problems. Tissue plasminogen activator (tPA) is an endogenous protein that has been shown to bind fibrin with high affinity and may circumvent antibody difficulties. Use of tPA-derived proteins or peptides, however, requires that the plasminogen-activating proteolytic activity be neutralized or removed. As an initial step in determining the feasibility of this targeting strategy, human recombinant tPA (Activase) was irreversibly inhibited with D-phe-L-pro-L-arg-chloromethyl ketone (PPACK) and conjugated to intrinsically echogenic liposomes (ELIP) by a thioether coupling protocol. Fibrin-binding affinities were assessed with a novel two-stage fibrin pad ELISA. We achieved 95-99% inactivation, while retaining both tPA fibrin-binding activities of K(D) approximately 2 nM and 33 nM. Thermodynamic analysis of the PPACK-inactivated tPA (tPA(P)) revealed highly exothermic interactions, indicative of ionic associations, especially for the higher affinity. The conjugation efficiency of tPA(P) to ELIP was within the range of that previously achieved for IgG and exhibited satisfactory fibrin targeting, characterized by striking increases of enthalpy and entropy increments. Evidence for coupling of noncovalent association energetics with the phosphatidylethanolamine major phase transition, observed in previous IgG antibody conjugations, was also evident in this case, but the nature of the transduction mechanism was different. These results demonstrate that tPA-derived components lacking proteolytic activity can be employed as fibrin-targeting agents for delivery of therapeutic and diagnostic formulations.
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Affiliation(s)
- Melvin E Klegerman
- Division of Cardiology, Department of Internal Medicine, University of Texas Health Science Center-Houston, Houston, TX 77030, USA.
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