Understanding the effects of formulation and process variables on the printlets quality manufactured by selective laser sintering 3D printing

The focus of the study was to understand the effects of formulation and process variables on the printlets quality manufactured by selective laser sintering (SLS) 3D printing. The Box-Behnken response surface methodology was used to evaluate effects of individual variables and combinations thereof. The formulation and process variables studied were printing chamber temperature (degrees C, X-1), laser scanning speed (mm/sec, X-2) and lactose monohydrate concentration (%, X-3). The responses studied were weight of printlets (mg, Y-1), hardness (N, Y-2), disintegration time (sec, Y-3) and dissolved drug fraction in 15 min (%, Y-4). The values of Y-1, Y-2, Y-3 and Y-4 varied from 170.2-257.0 mg, 5.5-32.0 N, 20-120 s and 64.4-97.5%, respectively. The studied factors showed statistically significant effects on the dependent variables (p < 0.04). The correlation coefficient between empirical and model predicted values for Y-1, Y-2, Y-3 and Y-4 were 0.999, 0.992, 0.998 and 0.983, respectively. The model was validated by an independent experiment and actual values of the responses were in close agreement with model predicted values. Fourier transformed infrared spectroscopy indicated no chemical interactions between the components of the formulation during printing process. X-ray powder diffractograms suggested a decrease in crystallinity of the drug and lactose in the printlets. Chemical images indicated uniform distribution of the drug. Scanning electron microscopy and X-ray micro-CT scanning showed a very porous microstructure of the printlets with a porosity of about 37.89%. In conclusion, the SLS method of manufacturing provides a feasible and flexible avenue for fabricating dosage forms with tailored characteristics.