FITC-Labeled Alendronate as an In Vivo Bone pH Sensor

Area of Science:

• Biomedical Engineering
• Sensing Technology
• Skeletal Biology

Background:

• Bone pH is crucial for physiological function and disease assessment.
• Noninvasive, real-time in vivo bone pH sensing remains a significant challenge.
• Existing methods lack specificity and temporal resolution for bone microenvironment monitoring.

Purpose of the Study:

• To develop and validate a novel fluorescent sensor for in vivo bone pH detection.
• To assess the sensor's specificity, biodistribution, and pH responsiveness in bone.
• To explore the potential application of the sensor in preclinical models of bone acidosis.

Main Methods:

• Synthesis of Alendronate-fluorescein isothiocyanate (Aln-FITC) bone pH sensor.
• In vitro assessment of Aln-FITC affinity for hydroxyapatite (HAp).
• In vivo biodistribution studies in rats via caudal vein injection.
• Evaluation of fluorescence intensity changes with varying pH in bone samples and acidosis models.

Main Results:

• Aln-FITC demonstrated selective binding to hydroxyapatite (HAp) over other calcium materials.
• Rapid and specific bone targeting of Aln-FITC in vivo, with sustained fluorescence for over 12 hours.
• Linear decrease in Aln-FITC fluorescence intensity with increasing pH (6-12) and specific responsiveness in the physiological bone pH range (6.8-7.4).
• Preliminary successful application in a nude mouse acidosis model, detecting bone pH alterations.

Conclusions:

• Aln-FITC is a promising, highly specific fluorescent probe for bone pH sensing.
• The sensor enables minimally invasive, real-time in vivo bone pH monitoring.
• Aln-FITC holds potential for preclinical research in bone healing, metabolism, and cancer mechanisms.