Heterostereocomplexes prepared from d-poly(lactide) and leuprolide. I. Characterization

Area of Science:

• Polymer Science
• Materials Science
• Biochemistry

Background:

• Stereoselective polymers and polypeptides with opposite enantiomeric configurations are crucial in advanced material applications.
• Understanding their interaction is key to developing novel materials and drug delivery systems.

Purpose of the Study:

• To characterize heterostereocomplexes formed between d-polylactic acid (d-PLA) and l-peptides.
• To develop a method for quantifying the relative interaction strength between stereoselective polymers and polypeptides.

Main Methods:

• Spontaneous precipitation from acetonitrile solution.
• Differential scanning calorimetry (DSC) for thermal analysis.
• Atomic force microscopy (AFM)-tapping mode for morphological imaging.
• Fluorescent spectrometry and confocal microscopy for peptide displacement analysis.

Main Results:

• DSC revealed two distinct melting points for the alpha (178°C) and beta (169°C) forms of PLA.
• A linear correlation was observed between melt enthalpy and peptide concentration.
• AFM imaging showed a morphological transition from a fibrous d-PLA network to uniform 100 nm disks of heterostereocomplex.
• Selective complexation of Rhodamine B-labeled leuprolide to d-PLA was confirmed, with subsequent displacement by l-PLA.

Conclusions:

• The study successfully characterized d-PLA/l-peptide heterostereocomplexes.
• A novel method was established to quantify interaction strengths between enantiomeric polymers and peptides.
• These findings offer insights into stereoselective interactions for material design and peptide complexation.