A Comparative Study of Mesoporous Silica and Mesoporous Bioactive Glass Nanoparticles as Non-Viral MicroRNA Vectors for Osteogenesis

Osteogenic and Antibacterial Response of Levofloxacin-Loaded Mesoporous Nanoparticles Functionalized with N-Acetylcysteine

Background/Objectives: Bone infection is one of the most prevalent complications in orthopedic surgery. This pathology is mostly due to bacterial pathogens, among which S. aureus stands out. The formation of a bacterial biofilm makes systemic treatment with antibiotics ineffective. Herein we propose a nanosystem composed of mesoporous bioactive glass nanoparticles (MBGN) loaded with levofloxacin and functionalized with N-acetylcysteine (NAC), aiming to offer an alternative to current treatments. These nanoparticles would present antibacterial activity able to disintegrate the biofilm and regenerate the peri-implantar osseous tissue. Methods: MBGN of composition 82.5 SiO2-17.5 CaO have been synthesized, loaded with levofloxacin, and functionalized with NAC (MBGN-L-NAC). The antimicrobial activity against mature S. aureus biofilms and bioactivity of the nanosystem have been evaluated, as well as its biocompatibility and ability to promote murine pre-osteoblastic MC3T3-E1 differentiation. Results: MBGNs exhibited high surface areas and radial mesoporosity, allowing up to 23.1% (% w/w) of levofloxacin loading. NAC was covalently bound keeping the mucolytic thiol group, SH, available. NAC and levofloxacin combination enhances the activity against S. aureus by disrupting mature biofilm integrity. This nanosystem was biocompatible with pre-osteoblasts, enhanced their differentiation towards a mature osteoblast phenotype, and promoted bio-mimetic mineralization under in vitro conditions. MBGN-L-NAC nanoparticles induced greater osteogenic response of osteoprogenitor cells through increased alkaline phosphatase expression, increased mineralization, and stimulation of pre-osteoblast nodule formation. Conclusions: MBGN-L-NAC exhibits a more efficient antibacterial activity due to the biofilm disaggregation exerted by NAC, which also contributes to enhance the osteoinductive properties of MBGNs, providing a potential alternative to conventional strategies for the management of bone infections.

Regulation of macrophage uptake through the bio-nano interaction using surface functionalized mesoporous silica nanoparticles with large radial pores

Porous nanoparticles, such as mesoporous silica nanoparticles (MSNs), have garnered significant interest for biomedical applications. Recently, MSNs with large radial pores have attracted increased attention because their unique pore structure and large pore size are suitable for delivering large molecules such as proteins and genes. Upon entry into biological systems like the bloodstream, nanoparticles quickly form a 'protein corona,' leading to alterations in their interactions with immune cells. In this study, we investigated the formation of protein corona on MSNs with large radial pores and various surface modifications using mass spectrometry. We also examined the effects of protein corona on the interaction between MSNs and macrophages. We prepared MSNs with large, cone-shaped radial pores (>30 nm) and six different functional groups, resulting in nanoparticles with neutral, negative, and positive surface charges. Our findings indicate that surface functional groups significantly alter the composition of the protein corona, affecting the bio-nano interaction of these surface-modified MSNs with macrophages. Notably, nanoparticles with similar surface charges exhibited distinct corona characteristics and were internalized differently by macrophages. This underscores the crucial role of the protein corona in determining the fate, behavior, and biological responses of nanoparticles. Our research sheds light on the significance of understanding and controlling protein corona formation to optimize the design and functionality of nanoparticle-based biomedical applications.

Nanoparticle-Mediated Gene Delivery for Bone Tissue Engineering

Critical-sized bone defects represent an urgent clinical problem, necessitating innovative treatment approaches. Gene-activated grafts for bone tissue engineering have emerged as a promising solution. However, traditional gene delivery methods are constrained by limited osteogenic efficacy and safety concerns. Recently, organic and inorganic nanoparticle (NP) vectors have attracted significant attention in bone tissue engineering for their safe, stable, and controllable gene delivery. Targeted gene delivery guided by insights into bone healing mechanisms, coupled with the multifunctional design of NPs, is crucial for enhancing therapeutic outcomes. Here, the theoretical foundations underlying NP-mediated gene therapy for enhancing bone healing across different histological stages are elucidated. Furthermore, the distinct attributes of functionalized NP vectors are discussed, and cutting-edge strategies aimed at optimizing gene delivery efficiency throughout the therapeutic process are highlighted. Additionally, the review addresses the unresolved challenges and prospects of this technology. This review may contribute to the continued development and clinical application of NP-mediated gene delivery for treating critical-sized bone defects.

Biomimetic siRNA nanogels for regulating macrophage polarization and promoting osteogenesis

Background

Bone fracture regeneration poses significant clinical challenges due to complications such as delayed healing, nonunion, and the limitations of current treatments.

Objective

This study introduces a novel therapeutic approach utilizing biomimetic nanogels to silence the Ccl4 gene, aiming to promote bone repair by regulating macrophage polarization.

Methods

The nanogels, composed of tannic acid (TA) and small interfering RNA (siRNA), were designed for targeted gene delivery.

Results

In vitro findings indicate that siRNA-mediated Ccl4 reduction significantly improves M2 macrophage polarization, which, in turn, promotes osteogenic differentiation of bone marrow-derived mesenchymal stem cells. Increased expression of osteogenic markers and enhanced mineral deposition were observed. The nanogels demonstrated optimal particle size, stability, and cellular uptake, and biocompatibility assays confirmed their non-toxicity.

Conclusion

This study underscores the potential of targeted siRNA delivery in modulating immune responses to enhance bone regeneration, offering promising treatment options for complex bone healing scenarios.

PEI/MMNs@LNA-542 nanoparticles alleviate ICU-acquired weakness through targeted autophagy inhibition and mitochondrial protection

Intensive care unit-acquired weakness (ICU-AW) is prevalent in critical care, with limited treatment options. Certain microRNAs, like miR-542, are highly expressed in ICU-AW patients. This study investigates the regulatory role and mechanisms of miR-542 in ICU-AW and explores the clinical potential of miR-542 inhibitors. ICU-AW models were established in C57BL/6 mice through cecal ligation and puncture (CLP) and in mouse C2C12 myoblasts through TNF-α treatment. In vivo experiments demonstrated decreased muscle strength, muscle fiber atrophy, widened intercellular spaces, and increased miR-542-3p/5p expression in ICU-AW mice model. In vitro experiments indicated suppressed ATG5, ATG7 and LC3II/I, elevated MDA and ROS levels, decreased SOD levels, and reduced MMP in the model group. Similar to animal experiments, the expression of miR-542-3p/5p was upregulated. Gel electrophoresis explored the binding of polyethyleneimine/mesoporous silica nanoparticles (PEI/MMNs) to locked nucleic acid (LNA) miR-542 inhibitor (LNA-542). PEI/MMNs@LNA-542 with positive charge (3.03 ± 0.363 mV) and narrow size (206.94 ± 6.19 nm) were characterized. Immunofluorescence indicated significant internalization with no apparent cytotoxicity. Biological activity, examined through intraperitoneal injection, showed that PEI/MMNs@LNA-542 alleviated muscle strength decline, restored fiber damage, and recovered mitochondrial injury in mice. In conclusion, PEI/MMNs nanoparticles effectively delivered LNA-542, targeting ATG5 to inhibit autophagy and alleviate mitochondrial damage, thereby improving ICU-AW.

Molecular Characterization of Mesoporous Silica (Un)loading by Gemcitabine and Ibuprofen - An Interplay of Salt-Bridges and Hydrogen Bonds

The molecular mechanisms of mesoporous silica nanomaterial (MSN) loading by gemcitabine and ibuprofen molecules, respectively, are elucidated as functions of pore geometry. Based on a small series of MSN archetypes, we use molecular dynamics simulations to systematically explore molecule-by-molecule loading of the carrier material. Apart from predicting the maximum active pharmaceutical ingredient (API) loading capacity, more detailed statistical analysis of the incorporation energy reveals dedicated profiles stemming from the interplay of guest-MSN salt-bridges/hydrogen bonding in concave and convex domains of the silica surfaces - which outcompete interactions among the drug molecules. Only after full coverage of the silica surface, we find secondary layer growth stabilized by guest-guest interactions exclusively. Based on molecular models, we thus outline a two-step type profile for drug release from MSN networks. Subject to the MSN structure, we find 50-75 % of the API within amorphous domains in the inner regions of the pores - from which drug release is provided at constant dissociation energy. In turn, the remaining 50-25 % of drug molecules are drastically hindered from dissociation.

Very Large Pore Mesoporous Bioactive Silicate Glasses: Comparison of Behavior toward Classical Mesoporous Bioactive Glasses in Terms of Drug Loading/Release and Bioactivity

Considering the increase in patients who suffer from osteoporosis and the bone defects that occur in these patients, bone tissue regeneration is a promising option to solve this problem. To achieve a synergistic effect between the synthesis of a proper structure and bioactive/pharmaceutical activity, ions with a physiological effect can be added to silica structures, such as Ca2+, thanks to its bioactive behavior, and Ga3+ for its antibacterial and anticancer action. In this work, the synthesis of large pore mesoporous silica (LPMS), potential bioactive glasses containing Ca2+ and Ga3+, has been studied. Corresponding structures, in terms of composition, have been synthesized following the Sol-Gel EISA (Evaporation Induced Self-Assembly) process (obtaining Classical Mesoporous Silica, MS). Pore structure characterization of LPMSs and MSs has been performed using N2 adsorption/desorption and Hg-porosimetry, showing the presence of pores for LPMSs in the range of 20-60 and 200-600 nm. Nisin, a polycyclic antibacterial peptide, has been used for load tests. The load and release tests performed highlight a higher loading and releasing, doubled for LPMSs if compared to MSs. To confirm the maintenance of the structure of LPMSs and their mechanical strength and resistance, scanning electron microscopy images were acquired before and after release tests. Ca and Ga release in SBF has been studied through inductively coupled plasma-optical emission spectroscopy (ICP-OES), showing a particularly high release of these ions performed with LPMSs. The bioactive behavior of Ca-containing structures has been confirmed using FT-IR (Fourier-transform infrared spectroscopy), SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy), and X-ray powder diffraction (XRDP). In conclusion, LPMSs showed better loading and releasing properties compared with classical MS and better release in terms of active ions. In addition, it has also been demonstrated that LPMSs have bioactive behavior (a well-known characteristic of MSs).

Nanocore-Shell Bone Filler Contained Mesoporous Silica Modified with Hydroxyapatite Precursors; Wrapped in a Natural Metal-Phenolic Network

Various therapeutic strategies have been developed to address bone diseases caused by aging society and skeletal defects caused by trauma or accidental events. One such approach is using bone fillers, such as hydroxyapatite (HA) and bioactive glasses. Although they have provided effective osteogenesis, infection and inflammation due to the surgical procedure and uncontrolled ion release can hinder the efficiency of bone regeneration. In response to these challenges, immobilizing a neutral metal-phenolic network on the surface of osteoconductive nanoparticles would be the master key to achieving a gradual, controlled release during the mineralization period and reducing infection and inflammation through biological pathways. In this regard, a mesoporous silica nanocomposite modified by an HA precursor was synthesized to enhance bone regeneration. In addition, to improve the therapeutic effects, its surface was wrapped with a magnesium-phenolic network made from pomegranate extract, which can simultaneously produce anti-inflammatory and antibacterial effects. The obtained core-shell nanocomposite was characterized by its physicochemical properties, biocompatibility, and bioactivity. The in vitro studies revealed that the synthesized nanocomposite exhibits higher osteogenic activity than the control groups, as confirmed by alizarin red staining. Moreover, the nanocomposite maintained low toxicity as measured by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and increased antibacterial activity against Staphylococcus aureus and Escherichia coli compared with the control groups. Therefore, this research presents a promising strategy for bone regeneration, combining the advantages of mesoporous silica nanocomposite modified by an HA precursor with the beneficial effects of a magnesium-phenolic network.

Mesoporous Core-Cone Silica Nanoparticles Can Deliver miRNA-26a to Macrophages to Exert Immunomodulatory Effects on Osteogenesis In Vitro

Nanoparticles can play valuable roles in delivering nucleic acids, including microRNAs (miRNA), which are small, non-coding RNA segments. In this way, nanoparticles may exert post-transcriptional regulatory influences on various inflammatory conditions and bone disorders. This study used biocompatible, core-cone-structured, mesoporous silica nanoparticles (MSN-CC) to deliver miRNA-26a to macrophages in order to influence osteogenesis in vitro. The loaded nanoparticles (MSN-CC-miRNA-26) showed low-level toxicity towards macrophages (RAW 264.7 cells) and were internalized efficiently, causing the reduced expression of pro-inflammatory cytokines, as seen via real-time PCR and cytokine immunoassays. The conditioned macrophages created a favorable osteoimmune environment for MC3T3-E1 preosteoblasts, driving osteogenic differentiation with enhanced osteogenic marker expression, alkaline phosphatase (ALP) production, extracellular matrix formation, and calcium deposition. An indirect co-culture system revealed that direct osteogenic induction and immunomodulation by MSN-CC-miRNA-26a synergistically increased bone production due to the crosstalk between MSN-CC-miRNA-26a-conditioned macrophages and MSN-CC-miRNA-26a-treated preosteoblasts. These findings demonstrate the value of nanoparticle delivery of miR-NA-26a using MSN-CC for suppressing the production of pro-inflammatory cytokines with macrophages and for driving osteogenic differentiation in preosteoblasts via osteoimmune modulation.

Mesoporous Silica Promotes Osteogenesis of Human Adipose-Derived Stem Cells Identified by a High-Throughput Microfluidic Chip Assay

Silicon-derived biomaterials are conducive to regulating the fate of osteo-related stem cells, while their effects on the osteogenic differentiation of human adipose-derived stem cells (hADSCs) remain inconclusive. Mesoporous silica (mSiO₂) is synthesized in a facile route that exhibited the capability of promoting osteogenic differentiation of hADSCs. The metabolism of SiO₂ in cells is proposed according to the colocalization fluorescence analysis between lysosomes and nanoparticles. The released silicon elements promote osteogenic differentiation. The detection of secretory proteins through numerous parallel experiments performed via a microfluidic chip confirms the positive effect of SiO₂ on the osteogenic differentiation of hADSCs. Moreover, constructed with superparamagnetic iron oxide (Fe₃O₄), the magnetic nanoparticles (MNPs) of Fe₃O₄@mSiO₂ endow the cells with magnetic resonance imaging (MRI) properties. The MNP-regulated osteogenic differentiation of autologous adipose-derived stem cells provides considerable clinical application prospects for stem cell therapy of bone tissue repair with an effective reduction in immune rejection.