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Charge and hydrophobicity effects of NIR fluorophores on bone-specific imaging.

Bao K, Nasr KA, Hyun H, Lee JH, Gravier J, Gibbs SL, Choi HS - Theranostics (2015)

Bottom Line: Pamidronate (PAM) has been widely used for this purpose because of its high binding affinity toward bone and remarkable therapeutic effects.Herein we describe the development of a series of PAM-conjugated NIR fluorophores that varied in net charges and hydrophobicity, and compared their bone targeting efficiency, biodistribution, and blood clearance.Since the targeting moiety, PAM, is highly negatively charged but small, the overall in vivo bone targeting and biodistribution were mediated by the physicochemical properties of conjugated fluorophores.

View Article: PubMed Central - PubMed

Affiliation: 1. Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215; ; 2. Key Laboratory of Structure-based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China, 110016;

ABSTRACT
Recent advances in near-infrared (NIR) fluorescence imaging enabled real-time intraoperative detection of bone metastases, bone growth, and tissue microcalcification. Pamidronate (PAM) has been widely used for this purpose because of its high binding affinity toward bone and remarkable therapeutic effects. Herein we describe the development of a series of PAM-conjugated NIR fluorophores that varied in net charges and hydrophobicity, and compared their bone targeting efficiency, biodistribution, and blood clearance. Since the targeting moiety, PAM, is highly negatively charged but small, the overall in vivo bone targeting and biodistribution were mediated by the physicochemical properties of conjugated fluorophores.

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Specificity of PAM-ZW800-1, PAM-CW800 and PAM-ZW800-3a for hydroxyapatite (HA) over other calcium salts. Each fluorophore was well mixed with calcium salts for 30 min and washed with excess of PBS prior to NIR fluorescence imaging. SBR was calculated by the fluorescence intensity of each fluorophore sample versus the signal intensity of each control sample (n = 3, mean ± s.d.). ***P < 0.001. Abbreviations: CC = calcium carbonate; CO = calcium oxalate; HA = hydroxyapatite; CP = calcium phosphate and CPP = calcium pyrophosphate.
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Figure 2: Specificity of PAM-ZW800-1, PAM-CW800 and PAM-ZW800-3a for hydroxyapatite (HA) over other calcium salts. Each fluorophore was well mixed with calcium salts for 30 min and washed with excess of PBS prior to NIR fluorescence imaging. SBR was calculated by the fluorescence intensity of each fluorophore sample versus the signal intensity of each control sample (n = 3, mean ± s.d.). ***P < 0.001. Abbreviations: CC = calcium carbonate; CO = calcium oxalate; HA = hydroxyapatite; CP = calcium phosphate and CPP = calcium pyrophosphate.

Mentions: In vitro calcium salt binding specificity. The specificity of PAM-ZW800-1, PAM-CW800, and PAM-ZW800-3a for hydroxyapatite (HA) over other calcium salts was determined using NIR fluorescence imaging. 5 μM of each PAM-NIR fluorophore was incubated with HA and calcium carbonate (CC), calcium oxalate (CO), calcium phosphate (CP), and calcium pyrophosphate (CPP) for 30 min at room temperature with constant shaking, then washed 3 times with a 100-fold excess of phosphate-buffered saline (PBS). As shown in Fig. 2, all the fluorophores demonstrated strong affinity for HA compared to other calcium salts. In addition, PAM-ZW800-1 exhibited higher SBR when binding to HA than the other two PAM fluorophore derivatives (Fig. 2). This increase in SBR for PAM-ZW800-1 and PAM-CW800 over PAM-ZW800-3a can be attributed to the improved calcium binding via salt formation through the phenyl sulfonate moieties in the fluorophore backbone 36,37. In addition, the hydroxyl group of HA contributes to the formation of strong hydrogen bonds with anions of fluorophores, which increased binding affinity significantly 36. Of note, PAM-ZW800-1 had 8-fold higher specificity toward HA over other calcium salts, and permits NIR fluorescence detection of HA with high sensitivity.


Charge and hydrophobicity effects of NIR fluorophores on bone-specific imaging.

Bao K, Nasr KA, Hyun H, Lee JH, Gravier J, Gibbs SL, Choi HS - Theranostics (2015)

Specificity of PAM-ZW800-1, PAM-CW800 and PAM-ZW800-3a for hydroxyapatite (HA) over other calcium salts. Each fluorophore was well mixed with calcium salts for 30 min and washed with excess of PBS prior to NIR fluorescence imaging. SBR was calculated by the fluorescence intensity of each fluorophore sample versus the signal intensity of each control sample (n = 3, mean ± s.d.). ***P < 0.001. Abbreviations: CC = calcium carbonate; CO = calcium oxalate; HA = hydroxyapatite; CP = calcium phosphate and CPP = calcium pyrophosphate.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4377729&req=5

Figure 2: Specificity of PAM-ZW800-1, PAM-CW800 and PAM-ZW800-3a for hydroxyapatite (HA) over other calcium salts. Each fluorophore was well mixed with calcium salts for 30 min and washed with excess of PBS prior to NIR fluorescence imaging. SBR was calculated by the fluorescence intensity of each fluorophore sample versus the signal intensity of each control sample (n = 3, mean ± s.d.). ***P < 0.001. Abbreviations: CC = calcium carbonate; CO = calcium oxalate; HA = hydroxyapatite; CP = calcium phosphate and CPP = calcium pyrophosphate.
Mentions: In vitro calcium salt binding specificity. The specificity of PAM-ZW800-1, PAM-CW800, and PAM-ZW800-3a for hydroxyapatite (HA) over other calcium salts was determined using NIR fluorescence imaging. 5 μM of each PAM-NIR fluorophore was incubated with HA and calcium carbonate (CC), calcium oxalate (CO), calcium phosphate (CP), and calcium pyrophosphate (CPP) for 30 min at room temperature with constant shaking, then washed 3 times with a 100-fold excess of phosphate-buffered saline (PBS). As shown in Fig. 2, all the fluorophores demonstrated strong affinity for HA compared to other calcium salts. In addition, PAM-ZW800-1 exhibited higher SBR when binding to HA than the other two PAM fluorophore derivatives (Fig. 2). This increase in SBR for PAM-ZW800-1 and PAM-CW800 over PAM-ZW800-3a can be attributed to the improved calcium binding via salt formation through the phenyl sulfonate moieties in the fluorophore backbone 36,37. In addition, the hydroxyl group of HA contributes to the formation of strong hydrogen bonds with anions of fluorophores, which increased binding affinity significantly 36. Of note, PAM-ZW800-1 had 8-fold higher specificity toward HA over other calcium salts, and permits NIR fluorescence detection of HA with high sensitivity.

Bottom Line: Pamidronate (PAM) has been widely used for this purpose because of its high binding affinity toward bone and remarkable therapeutic effects.Herein we describe the development of a series of PAM-conjugated NIR fluorophores that varied in net charges and hydrophobicity, and compared their bone targeting efficiency, biodistribution, and blood clearance.Since the targeting moiety, PAM, is highly negatively charged but small, the overall in vivo bone targeting and biodistribution were mediated by the physicochemical properties of conjugated fluorophores.

View Article: PubMed Central - PubMed

Affiliation: 1. Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215; ; 2. Key Laboratory of Structure-based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China, 110016;

ABSTRACT
Recent advances in near-infrared (NIR) fluorescence imaging enabled real-time intraoperative detection of bone metastases, bone growth, and tissue microcalcification. Pamidronate (PAM) has been widely used for this purpose because of its high binding affinity toward bone and remarkable therapeutic effects. Herein we describe the development of a series of PAM-conjugated NIR fluorophores that varied in net charges and hydrophobicity, and compared their bone targeting efficiency, biodistribution, and blood clearance. Since the targeting moiety, PAM, is highly negatively charged but small, the overall in vivo bone targeting and biodistribution were mediated by the physicochemical properties of conjugated fluorophores.

Show MeSH
Related in: MedlinePlus