The application of electrosprayed minocycline-loaded PLGA microparticles for the treatment of glioblastoma

Abstract

The survival of patients with glioblastoma multiforme (GBM), the most common and invasive form of malignant brain tumors, remains poor despite advances in current treatment methods including surgery, radiotherapy, and chemotherapy. Minocycline is a semi-synthetic tetracycline derivative that has been widely used as an antibiotic and more recently, it has been utilized as an antiangiogenic factor to inhibit tumorigenesis. The objective of this study was to investigate the utilization of electrospraying process to fabricate minocycline-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles with high drug loading and loading efficiency and to evaluate their ability to induce cell toxicity in human glioblastoma (i.e., U87-MG) cells. The results from this study demonstrated that solvent mixture of dicholoromethane (DCM) and methanol is the optimal solvent combination for minocycline and larger amount of methanol (i.e., 70:30) resulted in a higher drug loading. All three solvent ratios of DCM:methanol tested produced microparticles that were both spherical and smooth, all in the micron size range. The electrosprayed microparticles were able to elicit a cytotoxic response in U87-MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work provides proof of concept to the hypothesis that electrosprayed minocycline-loaded PLGA microparticles can be a promising agent for the treatment of GBM and could have potential application for cancer therapies.

Keywords: PLGA microparticles; drug delivery; electrospraying; glioblastoma; minocycline.

Figure 1.

Light microscopy and SEM images of the electrosprayed minocycline-loaded PLGA microparticles fabricated with different drug amount and collection method: A1-A4) Optical microscopy images (scale bar of these images represent 10 μm); B1-B4) SEM images with high magnification: B1) 2.5 mg_Decant, 926x, scale bar represents 10 μm, B2) 2.5 mg_Evaporation, 748x, scale bar represents 10 μm, B3) 4.0 mg_Decant, 800x, scale bar 10 μm, and B4) 4.0 mg_Evaporation, 1320x, scale bar 10 μm; C1-C4) SEM images with low magnification: C1) 2.5 mg_Decant, 81x, scale bar represents 200 μm, C2) 2.5 mg_Evaporation, 170x, scale bar represents 100 μm, C3) 4.0 mg_Decant, 80x, scale bar 100 μm, and C4) 4.0 mg_Evaporation, 258x, scale bar 20 μm.

Figure 2.

Optical microscopy and SEM images of the electrosprayed minocycline-loaded PLGA microparticles fabricated with different drug amount and collection method: A1-A3) Optical microscopy images (scale bar of these images represents 10 μm); B1-B3) SEM images with high magnification of : B1) 90:10, 618x, scale bar represents 20 μm, B2) 80:20, 748x, scale bar represents 10 μm and B3) 70:30, 1300x, scale bar 10 μm; C1-C3) SEM images with low magnification: C1) 90:10, 258x, scale bar represents 20 μm, C2) 80:20, 70x, scale bar represents 100 μm and C3) 70:30, 80x, scale bar 100 μm.

Figure 3.

SEM images of A) minocycline drug powder, 150x, scale bar represents 100 μm. B) minocycline that was dissolved in isopropanol and then the isopropanol was allowed to evaporate, 1840x, scale bar represents 3 μm (embedded picture: 735x, scale bar represents 20 μm) and C) decant solution where the isopropanol was allowed to evaporate, 3290x, scale bar represents 2 μm.

Figure 4.

FTIR spectra of A) PLGA, B) Minocycline, C) Minocycline-loaded PLGA microparticles and D) Powder after evaporating isopropanol.

Figure 5.

Cumulative release from A) 1 hr. to 14 d and B) 3 hr. to 14 d. Groups with different lowercase letters (i.e. ^a vs. ^b vs. ^c) are significantly different ($p<0.05$) from one another within a particular category. Amount released C) after 1 hr. and D) from 3 hr. to 14 d. ^# indicates groups that are statistically significantly different ($p<0.05$) from all other groups. The results are expressed as mean ± standard deviation for $n=3$ biological replicates and $n=3$ technical replicates.

Figure 6.

Cell viability of U-87 MG glioblastoma cells exposed to the minocycline only (denoted as FD), empty PLGA microparticles only (denoted as B) or minocycline-loaded PLGA microparticles (denoted as MP) for 72 hours. The results are expressed as mean ± standard deviation for $n=4$ biological replicates. ^# indicates groups that are statistically significantly different ($p<0.05$) from the control and empty PLGA microparticles within the same drug concentration. * indicates statistically significantly different ($p<0.05$) between groups indicated.