Effects of Surface Protein Adsorption on the Distribution and Retention of Intratumorally Administered Gold Nanoparticles

Simulated Gastrointestinal Fluids Impact the Stability of Polymer-Functionalized Selenium Nanoparticles: Physicochemical Aspects

Background

Selenium (Se) is a vital micronutrient for maintaining homeostasis in the human body. Selenium nanoparticles (SeNPs) have demonstrated improved bioavailability compared to both inorganic and organic forms of Se. Therefore, supplementing with elemental Se in its nano-form is highly promising for biomedical applications related to Se deficiency.

Purpose

The primary objective of this study was to evaluate the impact of the main gastrointestinal proteins on the physicochemical properties and stability of polymer-coated SeNPs.

Methods

SeNPs functionalized with thiolated chitosan or hyaluronic acid were characterized based on their composition, morphology, size, and zeta potential. The stability of these particles was evaluated in simulated gastric and intestinal fluids. Additionally, the interaction propensity between major gastric proteins, such as pepsin and pancreatin, and functionalized SeNPs was investigated with FTIR, fluorescence quenching titrations, and in situ adsorption measurements.

Results

The composition of the media, including pH and ionic strength, the chemistry of polymers, and the presence of the proteins, influence the size and zeta potential of the SeNPs. The increase in NP size due to the formation of large agglomerates, along with the decrease in zeta potential magnitude, confirmed the formation of a protein corona. Both pepsin and pancreatin showed a strong affinity to the particle surface. Based on the values of the apparent equilibrium dissociation constant this affinity was more pronounced for positively charged thiolated chitosan coated SeNPs compared to those coated with negatively charged hyaluronic acid. The polymer coated SeNPs displayed antioxidative potential, which could be very beneficial for health conditions associated with Se-deficiency.

Conclusion

This study highlights the importance of exploring the characteristics of polymer-functionalized SeNPs under gastrointestinal conditions. Such investigations are important for developing nutritional supplements that can gradually release Se from SeNPs, thereby improving selenium absorption, bioavailability, and safety.

An Insight into Perfusion Anisotropy within Solid Murine Lung Cancer Tumors

Blood vessels are essential for maintaining tumor growth, progression, and metastasis, yet the tumor vasculature is under a constant state of remodeling. Since the tumor vasculature is an attractive therapeutic target, there is a need to predict the dynamic changes in intratumoral fluid pressure and velocity that occur across the tumor microenvironment (TME). The goal of this study was to obtain insight into perfusion anisotropy within lung tumors. To achieve this goal, we used the perfusion marker Hoechst 33342 and vascular endothelial marker CD31 to stain tumor sections from C57BL/6 mice harboring Lewis lung carcinoma tumors on their flank. Vasculature, capillary diameter, and permeability distribution were extracted at different time points along the tumor growth curve. A computational model was generated by applying a unique modeling approach based on the smeared physical fields (Kojic Transport Model, KTM). KTM predicts spatial and temporal changes in intratumoral pressure and fluid velocity within the growing tumor. Anisotropic perfusion occurs within two domains: capillary and extracellular space. Anisotropy in tumor structure causes the nonuniform distribution of pressure and fluid velocity. These results provide insights regarding local vascular distribution for optimal drug dosing and delivery to better predict distribution and duration of retention within the TME.

Zonal Intratumoral Delivery of Nanoparticles Guided by Surface Functionalization

Delivery of small molecules and anticancer agents to malignant cells or specific regions within a tumor is limited by penetration depth and poor spatial drug distribution, hindering anticancer efficacy. Herein, we demonstrate control over gold nanoparticle (GNP) penetration and spatial distribution across solid tumors by administering GNPs with different surface chemistries at a constant injection rate via syringe pump. A key finding in this study is the discovery of different zone-specific accumulation patterns of intratumorally injected nanoparticles dependent on surface functionalization. Computed tomography (CT) imaging performed in vivo of C57BL/6 mice harboring Lewis lung carcinoma (LLC) tumors on their flank and gross visualization of excised tumors consistently revealed that intratumorally administered citrate-GNPs accumulate in particle clusters in central areas of the tumor, while GNPs functionalized with thiolated phosphothioethanol (PTE-GNPs) and thiolated polyethylene glycol (PEG-GNPs) regularly accumulate in the tumor periphery. Further, PEG functionalization resulted in larger tumoral surface coverage than PTE, reaching beyond the outer zone of the tumor mass and into the surrounding stroma. To understand the dissimilarities in spatiotemporal evolution across the different GNP surface chemistries, we modeled their intratumoral transport with reaction-diffusion equations. Our results suggest that GNP surface passivation affects nanoparticle reactivity with the tumor microenvironment, leading to differential transport behavior across tumor zones. The present study provides a mechanistic understanding of the factors affecting spatiotemporal distribution of nanoparticles in the tumor. Our proof of concept of zonal delivery within the tumor may prove useful for directing anticancer therapies to regions of biomarker overexpression.

Dialdehyde Starch Nanocrystals as a Novel Cross-Linker for Biomaterials Able to Interact with Human Serum Proteins

In recent years, new cross-linkers from renewable resources have been sought to replace toxic synthetic compounds of this type. One of the most popular synthetic cross-linking agents used for biomedical applications is glutaraldehyde. However, the unreacted cross-linker can be released from the materials and cause cytotoxic effects. In the present work, dialdehyde starch nanocrystals (NDASs) were obtained from this polysaccharide nanocrystal form as an alternative to commonly used cross-linking agents. Then, 5-15% NDASs were used for chemical cross-linking of native chitosan (CS), gelatin (Gel), and a mixture of these two biopolymers (CS-Gel) via Schiff base reaction. The obtained materials, forming thin films, were characterized by ATR-FTIR, SEM, and XRD analysis. Thermal and mechanical properties were determined by TGA analysis and tensile testing. Moreover, all cross-linked biopolymers were also characterized by hydrophilic character, swelling ability, and protein absorption. The toxicity of obtained materials was tested using the Microtox test. Dialdehyde starch nanocrystals appear as a beneficial plant-derived cross-linking agent that allows obtaining cross-linked biopolymer materials with properties desirable for biomedical applications.

Intratumoral Anti-PD-1 Nanoformulation Improves Its Biodistribution

Intratumoral administration of immune checkpoint inhibitors, such as programmed cell death-1 antibodies (aPD-1), is a promising approach toward addressing both the low patients' responses and high off-target toxicity, but good preclinical results have not translated in phase I clinical studies as significant off-target toxicities were observed. We hypothesized that the nanoformulation of aPD-1 could alter both their loco-regional and systemic distribution following intratumoral administration. To test this hypothesis, we developed an aPD-1 nanoformulation (aPD-1 NPs) and investigated its biodistribution following intratumoral injection in an orthotopic mice model of head and neck cancer. Biodistribution analysis demonstrated a significantly lower distribution in off-target organs of the nanoformulated aPD-1 compared to free antibodies. On the other hand, both aPD-1 NPs and free aPD-1 yielded a significantly higher tumor and tumor draining lymph node accumulation than the systemically administrated free aPD-1 used as the current clinical benchmark. In a set of comprehensive in vitro biological studies, aPD-1 NPs effectively inhibited PD-1 expression on T-cells to a similar extent to free aPD-1 and efficiently potentiated the cytotoxicity of T-cells against head and neck cancer cells in vitro. Further studies are warranted to assess the potential of this intratumoral administration of aPD-1 nanoformulation in alleviating the toxicity and enhancing the tumor efficacy of immune checkpoint inhibitors.

Formation of protein corona on interaction of pepsin with chitin nanowhiskers in simulated gastric fluid

Protein corona (PC) usually changes the physicochemical properties of nanoparticles (NPs) and determines their ultimate fate in the physiological environment. As NPs are widely used in food, it is important to obtain a deep understanding of PC formation in the gastrointestinal fluid. Herein, we explored the adsorption of pepsin to chitin nanowhiskers (CNWs) and their interactions in simulated gastric fluid. Results suggest that the binding of pepsin reduced the surface potential of CNWs from 22.4 ± 0.15 to 12.9 ± 0.51 mV and caused their aggregation. CNWs quenched the fluorescence of pepsin and induced slightly changes in its secondary structure containing a reduction in the β-sheet content (∼ 3%) and an increase in the random coils (∼ 2%). The isothermal titration calorimetry (ITC) data suggested that the interaction forces between CNWs and pepsin were mainly hydrogen bonds and van der Waals forces.

Radiolabeled Gold Nanoseeds Decorated with Substance P Peptides: Synthesis, Characterization and In Vitro Evaluation in Glioblastoma Cellular Models

Despite some progress, the overall survival of patients with glioblastoma (GBM) remains extremely poor. In this context, there is a pressing need to develop innovative therapy strategies for GBM, namely those based on nanomedicine approaches. Towards this goal, we have focused on nanoparticles (AuNP-SP and AuNP-SPTyr8) with a small gold core (ca. 4 nm), carrying DOTA chelators and substance P (SP) peptides. These new SP-containing AuNPs were characterized by a variety of analytical techniques, including TEM and DLS measurements and UV-vis and CD spectroscopy, which proved their high in vitro stability and poor tendency to interact with plasma proteins. Their labeling with diagnostic and therapeutic radionuclides was efficiently performed by DOTA complexation with the trivalent radiometals ⁶⁷Ga and ¹⁷⁷Lu or by electrophilic radioiodination with ¹²⁵I of the tyrosyl residue in AuNP-SPTyr8. Cellular studies of the resulting radiolabeled AuNPs in NKR1-positive GBM cells (U87, T98G and U373) have shown that the presence of the SP peptides has a crucial and positive impact on their internalization by the tumor cells. Consistently, ¹⁷⁷Lu-AuNP-SPTyr8 showed more pronounced radiobiological effects in U373 cells when compared with the non-targeted congener ¹⁷⁷Lu-AuNP-TDOTA, as assessed by cell viability and clonogenic assays and corroborated by Monte Carlo microdosimetry simulations.

Hyaluronate-Thiol Passivation Enhances Gold Nanoparticle Peritumoral Distribution When Administered Intratumorally in Lung Cancer

Biofouling is the unwanted adsorption of cells, proteins, or intracellular and extracellular biomolecules that can spontaneously occur on the surface of metal nanocomplexes. It represents a major issue in bioinorganic chemistry because it leads to the creation of a protein corona, which can destabilize a colloidal solution and result in undesired macrophage-driven clearance, consequently causing failed delivery of a targeted drug cargo. Hyaluronic acid (HA) is a bioactive, natural mucopolysaccharide with excellent antifouling properties, arising from its hydrophilic and polyanionic characteristics in physiological environments which prevent opsonization. In this study, hyaluronate-thiol (HA-SH) (MW 10 kDa) was used to surface-passivate gold nanoparticles (GNPs) synthesized using a citrate reduction method. HA functionalized GNP complexes (HA-GNPs) were characterized using absorption spectroscopy, scanning electron microscopy, zeta potential, and dynamic light scattering. GNP cellular uptake and potential dose-dependent cytotoxic effects due to treatment were evaluated in vitro in HeLa cells using inductively coupled plasma-optical emission spectrometry (ICP-OES) and trypan blue and MTT assays. Further, we quantified the in vivo biodistribution of intratumorally injected HA functionalized GNPs in Lewis Lung carcinoma (LLC) solid tumors grown on the flank of C57BL/6 mice and compared localization and retention with nascent particles. Our results reveal that HA-GNPs show overall greater peritumoral distribution (** p < 0.005, 3 days post-intratumoral injection) than citrate-GNPs with reduced biodistribution in off-target organs. This property represents an advantageous step forward in localized delivery of metal nano-complexes to the infiltrative region of a tumor, which may improve the application of nanomedicine in the diagnosis and treatment of cancer.

Improvements in Gold Nanorod Biocompatibility with Sodium Dodecyl Sulfate Stabilization

Due to their well-defined plasmonic properties, gold nanorods (GNRs) can be fabricated with optimal light absorption in the near-infrared region of the electromagnetic spectrum, which make them suitable for cancer-related theranostic applications. However, their controversial safety profile, as a result of surfactant stabilization during synthesis, limits their clinical translation. We report a facile method to improve GNR biocompatibility through the presence of sodium dodecyl sulfate (SDS). GNRs (120 × 40 nm) were synthesized through a seed-mediated approach, using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant to direct the growth of nanorods and stabilize the particles. Post-synthesis, SDS was used as an exchange ligand to modify the net surface charge of the particles from positive to negative while maintaining rod stability in an aqueous environment. GNR cytotoxic effects, as well as the mechanisms of their cellular uptake, were examined in two different cancer cell lines, Lewis lung carcinoma (LLC) and HeLa cells. We not only found a significant dose-dependent effect of GNR treatment on cell viability but also a time-dependent effect of GNR surfactant charge on cytotoxicity over the two cell lines. Our results promote a better understanding of how we can mediate the undesired consequences of GNR synthesis byproducts when exposed to a living organism, which so far has limited GNR use in cancer theranostics.