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

inflammatory responses. In this investigation, GelMA concentration ranged from a maximum of 74.0556 µg/
served as the cell-laden material, and it was observed that mL to a minimum of 0.3700 µg/mL (Figure 3B). Previous
the addition of PLGA MPs exacerbated the inflammatory studies have indicated that at lower concentrations
response in comparison to the GelMA control group, (0.1–10 nM), DEX can effectively counteract the damage
underscoring the significant contribution of synthetic inflicted on cartilage explants by inflammatory cytokines
materials to inflammation. In the study, PLGA was shaped such as TNF-α. At higher concentrations (100 nM to
into spherical structures with diameters ranging from 75 10μM), it is capable of inhibiting the loss of GAG in
to 100 μm to furnish mechanical support. This approach chondrocytes and maintaining cellular phenotype
not only reduced the quantity of PLGA employed but stability. This provides a clear biological basis for our
also rendered it more suitable for bioink components in selection of different experimental concentration
3D bioprinting. levels. 46,47 Therefore, the gradient concentrations of
In clinical practice, DEX is typically administered DEX-loaded porous microspheres were selected based
through traditional routes such as intramuscular or on this rationale. To choose the concentration of DEX,
intravenous injection. These administration routes have theoretical peak plasma concentration in clinical
some drawbacks, such as significant fluctuations in drug treatments (7.7 mM) was referenced to ensure that the
plasma concentrations. It has been reported that the usual experimental conditions are relevant to clinical scenarios,
injection frequency of conventional DEX is once daily thereby enhancing the potential for clinical translation of
or every other day to maintain stable pharmacological our findings. The experimental results indicate that all
48
effects. Dexamethasone exhibits a relatively large pulsatile three groups of drug-loaded microspheres possess anti-
range in blood plasma concentrations, which often reach inflammatory capabilities, and as the concentration of
peak levels within hours post-injection. According to the DEX increases, the anti-inflammatory efficacy gradually
literature, peak blood plasma concentrations of DEX can strengthens. Regarding cartilage formation ability
reach up to 2000 ng/mL, which rapidly decline to sub- (Figures 4 and 5B), PLGA-dex30 MPs@GelMA group
therapeutic levels within a few hours, leading to patient exhibited optimal cartilage formation capability. In this
discomfort and treatment burden. 41–43 In this study, DEX experiment, we set four different DEX concentrations.
was loaded on PLGA microsphere delivery systems. The results demonstrated that PLGA-dex30 MPs@GelMA
Considering the principle that a smaller average particle group exhibited an optimal balance in terms of drug
size of MPs leads to a more uniform drug distribution release efficiency, impact on cell viability, inflammatory
within the MPs and a larger surface area, thereby fostering response, and cartilage generation capabilities. This
greater drug dispersion on the MPs surface and increased concentration of MPs not only ensured effective drug
burst release, and aiming to prevent clogging of the delivery but also optimized the cellular and tissue
nozzle and achieve better printability in extrusion-based response to the material, indicating its suitability for 3D
3D bioprinting, we opted to regulate the particle size of printing and tissue engineering applications.
the MPs within the range of 75–100 μm. The results of
the in vitro release study reveal sustained drug release for In animal experiments, we subcutaneously implanted
a period exceeding 45 days. Superior sustained release rabbit chondrocytes into C57 mice for xenogeneic
capabilities, which enable continuous release of DEX transplantation and under the rabbit’s skin for
while maintaining therapeutic blood concentrations, autologous transplantation. We observed significantly
can significantly reduce patient discomfort, lower more pronounced inflammatory reactions and evident
treatment frequency, and enhance treatment convenience anti-inflammatory effects of DEX in the xenogeneic
and sustainability. 44,45 transplantation scenario. The initiation of the foreign
The concentration of DEX-loaded MPs is another body inflammatory response typically occurs within a
key factor. The daily release concentrations of the drug- few hours post-contact and may escalate within 24–48 h
loaded microspheres gradually transitioned from burst post-implantation. Studies indicate that the initial 14 days
release at the beginning of the testing to sustained release are pivotal for influencing tissue formation outcomes. 49,50
over time. Among them, the daily release concentration of Therefore, our focus was on monitoring the inflammatory
PLGA-dex15 MPs ranged from a maximum of 2.9720 µg/ response during this critical period. Throughout this
mL to a minimum of 0.0087 µg/mL; for the PLGA-dex30 time frame, DEX-loaded MPs consistently demonstrated
MPs group, the daily release concentration ranged from a anti-inflammatory effects, characterized by reduced
maximum of 38.2178 µg/mL to a minimum of 0.3700 µg/ expression of M1 macrophages and lower levels of
mL; and for the PLGA-dex60 MPs group, the daily release pro-inflammatory cytokines. 51

Volume 10 Issue 5 (2024) 401 doi: 10.36922/ijb.3396