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Oesophageal bioadhesion of sodium alginate suspensions: particle swelling and mucosal retention.

Oesophageal bioadhesion of sodium alginate suspensions: particle swelling and mucosal retention.

Eur J Pharm Sci. 2004 Sep;23(1):49-56.Richardson JC1, Dettmar PW, Hampson FC, Melia CD.
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Introduction 

This study explores the development of a bioadhesive liquid formulation designed to adhere specifically to the esophageal mucosa, offering a novel approach for localized drug delivery to the esophagus. The formulation contains sodium alginate, a swelling polymer, suspended in water-miscible vehicles. Upon dilution with saliva, the sodium alginate particles swell, forming a sticky, protective layer that adheres to the mucosal surface. 

Purpose of the Study 

The primary goal was to assess the swelling behavior and mucosal adhesion (mucoretention) of sodium alginate in various pharmaceutical solvents. Understanding these factors is crucial for designing effective oral bioadhesive treatments for esophageal disorders, such as acid reflux, esophagitis, or drug-induced injury. 

Methodology 

Sodium alginate (40% w/w) was suspended in four different vehicles: 

  •  Glycerol 
  •  Propylene Glycol 
  •  Polyethylene Glycol 200 (PEG 200) 
  •  Polyethylene Glycol 400 (PEG 400) 

To simulate real-world use, artificial saliva was used to dilute the formulations. Swelling behavior was monitored microscopically, with 1,9-dimethyl methylene blue (DMMB) acting as a staining agent for alginate particles. 

Key Findings 

1. Swelling Behavior 

  • Swelling of sodium alginate particles was initiated by saliva dilution. 
  •  Minimum dilution thresholds varied across vehicles: Glycerol: swelling began at 30% (w/w) dilution PEG 400: required nearly 60% (w/w) dilution 
  •  Swelling occurred when the Hildebrand solubility parameter of the diluted vehicle reached approximately 37 MPa^½. 

 2. Bioadhesion and Mucosal Retention 

  •  The ability of each formulation to adhere to esophageal tissue was assessed using an artificial saliva rinse. 
  •  All suspensions demonstrated high mucoretention. 
  •  Strong correlations were found between:
             Mucosal retention
             Minimum dilution needed for swelling 
            

Alginate in Stance Products

Conclusion 

 This research demonstrates the feasibility of designing saliva-activated bioadhesive suspensions for targeted drug delivery to the esophageal mucosa. By selecting vehicles with specific solubility characteristics, formulators can predict and optimize mucosal adhesion and polymer swelling behavior. 

 Such innovations have the potential to improve treatment of esophageal conditions by enhancing local drug residence time and reducing systemic side effects.

Scientific Articles swelling sodium alginate mucosa saliva