Page 398 - IJB-10-5

International Journal of Bioprinting DEX-Loaded PLGA microspheres enhance cartilage regeneration

peaks were observed in PLGA-dex0 MPs, whereas peaks commendable thermal stability under physiological
for the other groups exhibited escalation with increasing conditions at 37°C.
drug concentration during the fabrication of PLGA The alteration in the average molecular weight of
MPs, which were observed at 18.55, 21.16, and 21.69°C, PLGA during the in vitro degradation process of each
respectively. These features also reflect differences in the group of MPs is depicted in Figure 2K. Initially, there
content of DEX among the sample groups. were no notable differences in the molecular weight

Figure 2H and I illustrates the thermogravimetric of PLGA MPs among the groups post-preparation.
analysis (TGA) results of the MPs in each group. However, as the degradation time progressed, the
Performed under inert nitrogen conditions, TGA was molecular weight of all groups of PLGA MPs gradually
utilized to assess the thermal stability of the MPs in decreased. A considerable decline in molecular weight
each group, as indicated by residual mass and the rate was observed for all groups at week 4, indicating the
of weight change per unit temperature. As depicted in favorable degradability of the PLGA MPs prepared in
Figure 2H, the main degradation steps of MPs occurred this experiment. After 4 weeks, the molecular weight
had degraded to 20.53%, 19.87%, 19.41%, and 18.92% of
within the range of 190–370°C. The weight change rate the initial molecular weight for each group, respectively.
per unit temperature, with peak values observed at 322°C There were no statistically significant differences in
for PLGA MPs and 336°C for PLGA MPs loaded with molecular weight among the groups, suggesting that
DEX, signifies the maximum rate of weight change at drug loading has no significant impact on the molecular
these specific temperature points. The addition of DEX weight of the MPs. However, further measurements
led to an elevation in the temperature at which the MPs over an extended duration are warranted to monitor the
exhibited the most rapid weight loss. Examination of the degradation of PLGA MPs.
derivative thermogravimetric (DTG) curves depicted in
Figure 2I unveils primary peak positions for each group of The calculated results for the drug encapsulation
PLGA MPs at temperatures of 320.25, 335.58, 337.58, and efficiency of MPs and their pharmacokinetics are
335.92°C, respectively. The main peak displayed a sharp, summarized in Table 2, showcasing the average DEX
symmetrical, single-peak shape, indicating a clear single- content of 0 µg DEX/mg (PLGA-dex0 MPs@GelMA),
peak thermal decomposition process at this temperature, 25.3 ± 4.9 µg DEX/mg (PLGA-dex15 MPs), 66.5 ± 6.8 µg
DEX/mg (PLGA-dex30 MPs), and 152.5 ± 11.7 µg DEX/
characterized by steep peaks on both sides. From these mg MPs (PLGA-dex60 MPs). The sustained release system
findings, it can be inferred that the onset temperature of employed in this study facilitated a minimum of 45 days
thermal decomposition for PLGA-dex0 MPs was lower, of drug control release (Figure 3C), with drug release
while the onset temperature for the other three groups rates achieving 83.07% (PLGA-dex15@GelMA), 84.62%
of PLGA MPs was relatively higher, with peak positions (PLGA-dex30@GelMA), and 88.89% (PLGA-dex60 MPs),
observed in close proximity within the temperature range. respectively. The drug released within the initial 24 h for

As depicted in Figure 2J, the differential scanning PLGA-dex15 MPs, PLGA-dex30 MPs, and PLGA-dex60
calorimetry (DSC) curves of PLGA MPs with varying MPs groups were approximately 47.17%, 54.75%, and
concentrations of DEX did not manifest fixed melting 26.17%, respectively.
points, confirming that the PLGA used in this experiment To further elucidate the release capacity of each group
is an amorphous polymer material. The Tg values were for DEX (Figure 3A–C), the MPs were subjected to in
determined to be 53.86, 48.86, 51.86, and 52.86°C, vitro incubation, and the concentration of DEX in the
respectively. The endothermic peaks for all concentrations incubation solution was measured to study the release
of drug-loaded MPs appeared beyond 50°C, indicating kinetics of DEX from the MPs. Figure 3A demonstrates

Table 2. Drug loading (μg DEX/mg MPs) and encapsulation efficiency of each group (n = 3).
Group Percentage encapsulation Drug loading rate (%) The content of dexamethasone per milligram of
efficiency (%) porous microspheres.
(μg DEX/mg MPs)
PLGA-dex0 MPs 0 0 0
PLGA-dex15 MPs 0.84 0.059 25.3 ± 4.9
PLGA-dex30 MPs 1.11 0.14 66.5 ± 6.8
PLGA-dex60 MPs 1.27 0.29 152.5 ± 11.7

Volume 10 Issue 5 (2024) 390 doi: 10.36922/ijb.3396