Evaluation of Nanoparticle Penetration in the Tumor Spheroid Using Two-Photon Microscopy

Receptor Ligand-Free Mesoporous Silica Nanoparticles: A Streamlined Strategy for Targeted Drug Delivery across the Blood-Brain Barrier

Mesoporous silica nanoparticles (MSNs) represent a promising avenue for targeted brain tumor therapy. However, the blood-brain barrier (BBB) often presents a formidable obstacle to efficient drug delivery. This study introduces a ligand-free PEGylated MSN variant (RMSN25-PEG-TA) with a 25 nm size and a slight positive charge, which exhibits superior BBB penetration. Utilizing two-photon imaging, RMSN25-PEG-TA particles remained in circulation for over 24 h, indicating significant traversal beyond the cerebrovascular realm. Importantly, DOX@RMSN25-PEG-TA, our MSN loaded with doxorubicin (DOX), harnessed the enhanced permeability and retention (EPR) effect to achieve a 6-fold increase in brain accumulation compared to free DOX. In vivo evaluations confirmed the potent inhibition of orthotopic glioma growth by DOX@RMSN25-PEG-TA, extending survival rates in spontaneous brain tumor models by over 28% and offering an improved biosafety profile. Advanced LC-MS/MS investigations unveiled a distinctive protein corona surrounding RMSN25-PEG-TA, suggesting proteins such as apolipoprotein E and albumin could play pivotal roles in enabling its BBB penetration. Our results underscore the potential of ligand-free MSNs in treating brain tumors, which supports the development of future drug-nanoparticle design paradigms.

Overcoming the Blood-Brain Tumor Barrier with Docetaxel-Loaded Mesoporous Silica Nanoparticles for Treatment of Temozolomide-Resistant Glioblastoma

While temozolomide (TMZ) has been a cornerstone in the treatment of newly diagnosed glioblastoma (GBM), a significant challenge has been the emergence of resistance to TMZ, which compromises its clinical benefits. Additionally, the nonspecificity of TMZ can lead to detrimental side effects. Although TMZ is capable of penetrating the blood-brain barrier (BBB), our research addresses the need for targeted therapy to circumvent resistance mechanisms and reduce off-target effects. This study introduces the use of PEGylated mesoporous silica nanoparticles (MSN) with octyl group modifications (C8-MSN) as a nanocarrier system for the delivery of docetaxel (DTX), providing a novel approach for treating TMZ-resistant GBM. Our findings reveal that C8-MSN is biocompatible in vitro, and DTX@C8-MSN shows no hemolytic activity at therapeutic concentrations, maintaining efficacy against GBM cells. Crucially, in vivo imaging demonstrates preferential accumulation of C8-MSN within the tumor region, suggesting enhanced permeability across the blood-brain tumor barrier (BBTB). When administered to orthotopic glioma mouse models, DTX@C8-MSN notably prolongs survival by over 50%, significantly reduces tumor volume, and decreases side effects compared to free DTX, indicating a targeted and effective approach to treatment. The apoptotic pathways activated by DTX@C8-MSN, evidenced by the increased levels of cleaved caspase-3 and PARP, point to a potent therapeutic mechanism. Collectively, the results advocate DTX@C8-MSN as a promising candidate for targeted therapy in TMZ-resistant GBM, optimizing drug delivery and bioavailability to overcome current therapeutic limitations.

Nanofunctionalized Microparticles for Glucose Delivery in Three-Dimensional Cell Assemblies

Three-dimensional (3D) cell assemblies, such as multicellular spheroids, can be powerful biological tools to closely mimic the complexity of cell-cell and cell-matrix interactions in a native-like microenvironment. However, potential applications of large spheroids are limited by the insufficient diffusion of oxygen and nutrients through the spheroids and, thus, result in the formation of a necrotic core. To overcome this drawback, we present a new strategy based on nanoparticle-coated microparticles. In this study, microparticles function as synthetic centers to regulate the diffusion of small molecules, such as oxygen and nutrients, within human mesenchymal stem cell (hMSC) spheroids. The nanoparticle coating on the microparticle surface acts as a nutrient reservoir to release glucose locally within the spheroids. We first coated the surface of the poly(lactic-co-glycolic acid) (PLGA) microparticles with mesoporous silica nanoparticles (MSNs) based on electrostatic interactions and then formed cell-nanofunctionalized microparticle spheroids. Next, we investigated the stability of the MSN coating on the microparticles' surface during 14 days of incubation in cell culture medium at 37 °C. Then, we evaluated the influence of MSN-coated PLGA microparticles on spheroid aggregation and cell viability. Our results showed the formation of homogeneous spheroids with good cell viability. As a proof of concept, fluorescently labeled glucose (2-NBD glucose) was loaded into the MSNs at different concentrations, and the release behavior was monitored. For cell culture studies, glucose was loaded into the MSNs coated onto the PLGA microparticles to sustain local nutrient release within the hMSC spheroids. In vitro results demonstrated that the local delivery of glucose from MSNs enhanced the cell viability in spheroids during a short-term hypoxic culture. Taken together, the newly developed nanofunctionalized microparticle-based delivery system may offer a versatile platform for local delivery of small molecules within 3D cellular assemblies and, thus, improve cell viability in spheroids.

Microfluidic Devices: A Tool for Nanoparticle Synthesis and Performance Evaluation

The use of nanoparticles (NPs) in nanomedicine holds great promise for the treatment of diseases for which conventional therapies present serious limitations. Additionally, NPs can drastically improve early diagnosis and follow-up of many disorders. However, to harness their full capabilities, they must be precisely designed, produced, and tested in relevant models. Microfluidic systems can simulate dynamic fluid flows, gradients, specific microenvironments, and multiorgan complexes, providing an efficient and cost-effective approach for both NPs synthesis and screening. Microfluidic technologies allow for the synthesis of NPs under controlled conditions, enhancing batch-to-batch reproducibility. Moreover, due to the versatility of microfluidic devices, it is possible to generate and customize endless platforms for rapid and efficient in vitro and in vivo screening of NPs' performance. Indeed, microfluidic devices show great potential as advanced systems for small organism manipulation and immobilization. In this review, first we summarize the major microfluidic platforms that allow for controlled NPs synthesis. Next, we will discuss the most innovative microfluidic platforms that enable mimicking in vitro environments as well as give insights into organism-on-a-chip and their promising application for NPs screening. We conclude this review with a critical assessment of the current challenges and possible future directions of microfluidic systems in NPs synthesis and screening to impact the field of nanomedicine.

Advances in the study of spheroids as versatile models to evaluate biological interactions of inorganic nanoparticles

Spheroids are in vitro three-dimensional multicellular microstructures able to mimic the biological microenvironment, including the complexity of tumor architecture. Therefore, results closer to those expected for in vivo organisms can be reached using spheroids compared to the cell culture monolayer model. Inorganic nanoparticles (NPs) have also been playing relevant roles in the comprehension of biological processes. Moreover, they have been probed as novel diagnostic and therapeutical nanosystems. In this context, in this review, we present applications, published in the last five years, which show that spheroids can be versatile models to study and evaluate biological interactions involving inorganic NPs. Applications of spheroids associated with (i) basic studies to assess the penetration profile of nanostructures, (ii) the evaluation of NP toxicity, and (iii) NP-based therapeutical approaches are described. Fundamentals of spheroids and their formation methods are also included. We hope that this review can be a reference and guide future investigations related to this interesting three-dimensional biological model, favoring advances to Nanobiotechnology.

Uptake of Functional Ultrasmall Gold Nanoparticles in 3D Gut Cell Models

Ultrasmall gold nanoparticles (2 nm) easily penetrate the membranes of intestinal murine epithelial cells (MODE-K) and colorectal cancer cells (CT-26). They are also taken up by 3D spheroids (400 µm) of these cell types and primary gut organoids (500 µm). In contrast, dissolved dyes are not taken up by any of these cells or 3D structures. The distribution of fluorescent ultrasmall gold nanoparticles inside cells, spheroids, and gut organoids is examined by confocal laser scanning microscopy. Nanoparticles conjugated with the cytostatic drug doxorubicin and a fluorescent dye exhibit significantly greater cytotoxicity toward CT-26 tumor spheroids than equally concentrated dissolved doxorubicin, probably because they enter the interior of a spheroid much more easily than dissolved doxorubicin. Comprehensive analyses show that the cellular uptake of ultrasmall gold nanoparticles occurs by different endocytosis pathways.

Real-time in vivo imaging reveals specific nanoparticle target binding in a syngeneic glioma mouse model

Nanomaterial-based drug delivery is a promising strategy for glioma treatment. However, the detailed dynamics of nanoparticles in solid glioma are still a mystery, including their intratumoral infiltration depth, penetration, retention time, and distribution. Revealing these processes in detail requires repeated intravital imaging of the corresponding brain tumor regions over time during glioma growth. Hereby, we established a syngeneic orthotopic cerebral glioma mouse model by combining the chronic cranial window and two-photon microscopy. Thus, we were able to investigate the dynamics of the nanoparticles during long-term glioma growth. Three hours after the intravenous (i.v.) injection of integrin α_Vβ₃ binding conjugated silicon nanoparticles (SNPs-PEG-RGD-FITC), green nanoparticles had already infiltrated the brain glioma, and then more nanoparticles penetrated into the solid brain tumor and were retained for at least 8 days. However, the amount of control SNPs-PEG-FITC that infiltrated into the solid brain tumor was very low. Moreover, we found that SNPs-PEG-RGD-FITC were not only located in the tumor border but could also infiltrate into the core region of the solid tumor. In vitro assay also confirmed the high binding affinity between GL-261-Tdtomato cells and SNPs-PEG-RGD-FITC. Our results indicate that SNPs-PEG-RGD-FITC has high penetration and retention in a solid glioma and our model provides novel ideas for the investigation of nanoparticle dynamics in brain tumors.

Engineering biomolecular systems: Controlling the self-assembly of gelatin to form ultra-small bioactive nanomaterials

The size of nanocarriers determines the biological property of the materials, especially as it relates to intratumoral distribution. Previous research has shown that sizes of 10–50 nm penetrate deep inside the tumor, resulting in better efficacy. On the other hand, studies have shown that gelatin exhibits excellent biological properties, including compatibility, degradability, and toxicity. Therefore, FDA approved gelatin as a safe material to use as an excipient in injectables. The bottleneck is the nonexistence of smaller-sized gelatin nanoparticles (GNPs) to realize the full potential of these biomaterials. Yet, GNPs with sizes of less than 50 nm have not been reported; the synthetic strategy reported in the literature uses “uncontrolled crosslinking coupled with nanoprecipitation”, resulting in larger particle size. We have developed a new method to self-assemble gelatin strands by using an anionic, phosphate-based crosslinker and controlled precipitation. The method we developed produced ultra-small gelatin nanoparticles (G^X) of size 10 nm with a high degree of reproducibility, and it was characterized using dynamic light scattering (DLS), Energy-dispersive X-ray spectroscopy (EDS), High-resolution transmission, and scanning electron microscopy (HR-TEM/STEM). We also explored G^X as a bioactive platform to encapsulate imaging and therapy agents within the cavity. Interestingly, we were able to encapsulate 2 nm size gold nanoparticles within the void of G^X. The versatile nature of the G^X particles was further demonstrated by surface functionalizing with larger size gelatin nanoparticles to form core-satellite nanocomposites. Additionally, we studied the tumor penetrability of dye-tagged 10, 50, and 200 nm gelatin nanoparticles. The study showed that smaller size gelatin nanoparticles penetrate deeper tumor regions than larger particles. In general, G^X was efficient in penetrating the inner region of the spheroids. The results demonstrate the potential capabilities of ultra-small G^X nanoparticles for multi-staged payload delivery, diagnostics, and cancer therapy.

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Synthesized 10 nm-size gelatin nanoparticles (G^X) using controlled self-assembly process.

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G^X was used as a platform to encapsulate imaging and therapeutic agents. In addition, smaller size gold nanoparticles also were encapsulated.

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The surface of G^X was used to attach with gold or larger size gelatin nanoparticles.

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Using tumor spheroids, we demonstrated that G^X show enhanced enhancedtumor penetrability.

Multicellular Ovarian Cancer Model for Evaluation of Nanovector Delivery in Ascites and Metastatic Environments

A novel multicellular model composed of epithelial ovarian cancer and fibroblast cells was developed as an in vitro platform to evaluate nanovector delivery and ultimately aid the development of targeted therapies. We hypothesized that the inclusion of peptide-based scaffold (PuraMatrix) in the spheroid matrix, to represent in vivo tumor microenvironment alterations along with metastatic site conditions, would enhance spheroid cell growth and migration and alter nanovector transport. The model was evaluated by comparing the growth and migration of ovarian cancer cells exposed to stromal cell activation and tissue hypoxia. Fibroblast activation was achieved via the TGF-β1 mediated pathway and tissue hypoxia via 3D spheroids incubated in hypoxia. Surface-modified nanovector transport was assessed via fluorescence and confocal microscopy. Consistent with previous in vivo observations in ascites and at distal metastases, spheroids exposed to activated stromal microenvironment were denser, more contractile and with more migratory cells than nonactivated counterparts. The hypoxic conditions resulted in negative radial spheroid growth over 5 d compared to a radial increase in normoxia. Nanovector penetration attenuated in PuraMatrix regardless of surface modification due to a denser environment. This platform may serve to evaluate nanovector transport based on ovarian ascites and metastatic environments, and longer term, it provide a means to evaluate nanotherapeutic efficacy.

Iodine containing porous organosilica nanoparticles trigger tumor spheroids destruction upon monochromatic X-ray irradiation: DNA breaks and K-edge energy X-ray

X-ray irradiation of high Z elements causes photoelectric effects that include the release of Auger electrons that can induce localized DNA breaks. We have previously established a tumor spheroid-based assay that used gadolinium containing mesoporous silica nanoparticles and synchrotron-generated monochromatic X-rays. In this work, we focused on iodine and synthesized iodine-containing porous organosilica (IPO) nanoparticles. IPO were loaded onto tumor spheroids and the spheroids were irradiated with 33.2 keV monochromatic X-ray. After incubation in CO₂ incubator, destruction of tumor spheroids was observed which was accompanied by apoptosis induction, as determined by the TUNEL assay. By employing the γH2AX assay, we detected double strand DNA cleavages immediately after the irradiation. These results suggest that IPO first generate double strand DNA breaks upon X-ray irradiation followed by apoptosis induction of cancer cells. Use of three different monochromatic X-rays having energy levels of 33.0, 33.2 and 33.4 keV as well as X-rays with 0.1 keV energy intervals showed that the optimum effect of all three events (spheroid destruction, apoptosis induction and generation of double strand DNA breaks) occurred with a 33.2 keV monochromatic X-ray. These results uncover the preferential effect of K-edge energy X-ray for tumor spheroid destruction mediated by iodine containing nanoparticles.