Purdue Letter Logo Kinam Park PLGA Types

 

PLGA Characterization  
   L:G Ratio & Molecular Weight
   Linear vs. Star-Shape
   Solvent Solubility
   Drug Interactions

L:G Ratio & Molecular Weight

Molecuar Weight

Inherent viscosity average molecular weight (Lactel)
   If the relationship between the molecular weight measured by light scattering or GPC and viscosity average molecuar weight is established, the lattter can be used to confirm that a new batch of polymers synthesized has the molecular weight measured by other means. Many commercial products simply describes a range of viscosity average molecular weight, e.g., inherent viscosity of 0.95-1.20 for PLGA with L:G ratio of 50:50, because it is the easiest and fastest way of measuring the polymer molecular weight.
    Inherent Viscosity (IV) is a viscometric method for measuring molecular size. IV is based on the flow time of a polymer solution through a narrow capillary relative to the flow time of the pure solvent through the capillary. The units of IV are typically reported in deciliters per gram (dL/g). IV is simple and inexpensive to obtain and reproducible between different laboratories
    Gel Permeation Chromatography (GPC) is a chromatographic method for measuring molecular size. The molecular size can be expressed as molecular weight (MW) obtained from calibration with a standard polymer such as polystyrene. MWs obtained by GPC are very method-dependent and are much less reproducible between laboratories.
   These six plots are empirical correlations between IV and MW measured for six polymer compositions produced by Durect Corporation. The IV data for the 50:50 poly(DL-lactide-co-glycolide) and 65:35 poly(DL-lactide-co-glycolide) were obtained in hexafluoroisopropanol (HFIP). The IV data for the four remaining polymer compositions were obtained in chloroform. All GPC data for these plots were obtained in chloroform using polystyrene calibration standards. It is important to note that these are empirical correlations between IVs and MWs. MWs obtained under conditions different from those use in our laboratory may not match the correlation shown here.

Linear vs. Star-Shape

 

Solvent Solubility

 

Drug Interactions