Strategies to Regulate the Degradation and Clearance of Mesoporous Silica Nanoparticles: A Review

Mesoporous silica nanoparticles (MSNs) have attracted extensive attention as drug delivery systems because of their unique meso-structural features (high specific surface area, large pore volume, and tunable pore structure), easily modified surface, high drug-loading capacity, and sustained-release profiles. However, the enduring and non-specific enrichment of MSNs in healthy tissues may lead to toxicity due to their slow degradability and hinder their clinical application. The emergence of degradable MSNs provided a solution to this problem. The understanding of strategies to regulate degradation and clearance of these MSNs for promoting clinical trials and expanding their biological applications is essential. Here, a diverse variety of degradable MSNs regarding considerations of physiochemical properties and doping strategies of degradation, the biodistribution of MSNs in vivo, internal clearance mechanism, and adjusting physical parameters of clearance are highlighted. Finally, an overview of these degradable and clearable MSNs strategies for biosafety is provided along with an outlook of the encountered challenges.

Albumin Hydrogel-Coated Mesoporous Silica Nanoparticle as a Carrier of Cationic Porphyrin and Ratiometric Fluorescence pH Sensor

Here, we report that a mesoporous silica nanoparticle (MSN) coated with a fluoresceine-labeled bovine serum albumin (F-BSA) hydrogel layer works as a temperature-responsive nanocarrier for tetrakis-N-methylpyridyl porphyrin (TMPyP) and as a fluorescence ratiometric pH probe. F-BSA hydrogel-coated MSN containing TMPyP (F-BSA/MSN/TMPyP) was synthesized by thermal gelation of denatured F-BSA on the external surface of MSN. The F-BSA hydrogel layer was composed of an inner hard corona layer and an outer soft layer and was stable under physiological conditions. F-BSA/MSN/TMPyP exhibited temperature-dependent exponential release of TMPyP. In this release profile, the MSN was found to be a suitable host for stable encapsulation of tetracationic TMPyP by electrostatic interactions, and the F-BSA hydrogel layer mediated the diffusion of TMPyP from the MSN pore interior into the solution phase. Increasing temperature promoted partitioning of TMPyP from the pore interior to the F-BSA hydrogel layer, from where it was spontaneously released into the bulk solution phase by cation exchange. F-BSA/MSN/TMPyP also gave a linear ratiometric fluorescence response (1.3 per pH unit) in the pH range from 6.1 to 8.9.

Prospects and hazards of silica nanoparticles: Biological impacts and implicated mechanisms

With the thrive of nanotechnology, silica nanoparticles (SiNPs) have been extensively adopted in the agriculture, food, cosmetic, and even biomedical industries. Due to the mass production and use, SiNPs inevitably entered the environment, resulting in ecological toxicity and even posing a threat to human health. Although considerable investigations have been conducted to assess the toxicity of SiNPs, the correlation between SiNPs exposure and consequent health risks remains ambiguous. Since the biological impacts of SiNPs can differ from their design and application, the toxicity assessment for SiNPs may be extremely difficult. This review discussed the application of SiNPs in different fields, especially their biomedical use, and documented their potential release pathways into the environment. Meanwhile, the current process of assessing SiNPs-related toxicity on various model organisms and cell lines was also detailed, thus estimating the health threats posed by SiNPs exposure. Finally, the potential toxic mechanisms of SiNPs were also elaborated based on results obtained from both in vivo and in vitro trials. This review generally summarizes the biological effects of SiNPs, which will build up a comprehensive perspective of the application and toxicity of SiNPs.

Human Papilloma Virus DNA Detection in Clinical Samples Using Fluorogenic Probes Based on Oligonucleotide Gated Nanoporous Anodic Alumina Films

In this work, fluorogenic probes based on oligonucleotide capped nanoporous anodic alumina films are developed for specific and sensitive detection of human papilloma virus (HPV) DNA. The probe consists of anodic alumina nanoporous films loaded with the fluorophore rhodamine B (RhB) and capped with oligonucleotides bearing specific base sequences complementary to genetic material of different high-risk (hr) HPV types. Synthesis protocol is optimized for scale up production of sensors with high reproducibility. The sensors' surfaces are characterized by scanning electron microscopy (HR-FESEM) and atomic force microscopy (AFM) and their atomic composition is determined by energy dispersive X-ray spectroscopy (EDXS). Oligonucleotide molecules onto nanoporous films block the pores and avoid diffusion of RhB to the liquid phase. Pore opening is produced when specific DNA of HPV is present in the medium, resulting in RhB delivery, that is detected by fluorescence measurements. The sensing assay is optimized for reliable fluorescence signal reading. Nine different sensors are synthesized for specific detection of 14 different hr-HPV types in clinical samples with very high sensitivity (100%) and high selectivity (93-100%), allowing rapid screening of virus infections with very high negative predictive values (100%).

Ordered Mesoporous Electrodes for Sensing Applications

Electrochemical sensors have become increasingly relevant in fields such as medicine, environmental monitoring, and industrial process control. Selectivity, specificity, sensitivity, signal reproducibility, and robustness are among the most important challenges for their development, especially when the target compound is present in low concentrations or in complex analytical matrices. In this context, electrode modification with Mesoporous Thin Films (MTFs) has aroused great interest in the past years. MTFs present high surface area, uniform pore distribution, and tunable pore size. Furthermore, they offer a wide variety of electrochemical signal modulation possibilities through molecular sieving, electrostatic or steric exclusion, and preconcentration effects which are due to mesopore confinement and surface functionalization. In order to fully exploit these advantages, it is central to develop reproducible routes for sensitive, selective, and robust MTF-modified electrodes. In addition, it is necessary to understand the complex mass and charge transport processes that take place through the film (particularly in the mesopores, pore surfaces, and interfaces) and on the electrode in order to design future intelligent and adaptive sensors. We present here an overview of MTFs applied to electrochemical sensing, in which we address their fabrication methods and the transport processes that are critical to the electrode response. We also summarize the current applications in biosensing and electroanalysis, as well as the challenges and opportunities brought by integrating MTF synthesis with electrode microfabrication, which is critical when moving from laboratory work to in situ sensing in the field of interest.

Recent developments in visible light induced polymerization towards its application to nanopores

Visible light induced polymerizations are a strongly emerging field in recent years. Besides the often mild reaction conditions, visible light offers advantages of spatial and temporal control over chain growth, which makes visible light ideal for functionalization of surfaces and more specifically of nanoscale pores. Current challenges in nanopore functionalization include, in particular, local and highly controlled polymer functionalizations. Using spatially limited light sources such as lasers or near field modes for light-induced polymer functionalization is envisioned to allow local functionalization of nanopores and thereby improve nanoporous material performance. These light sources are usually providing visible light while classical photopolymerizations are mostly based on UV-irradiation. In this review, we highlight developments in visible light induced polymerizations and especially in visible light induced controlled polymerizations as well as their potential for nanopore functionalization. Existing examples of visible light induced polymerizations in nanopores are emphasized.

Tuning Mesoporous Silica Nanoparticles in Novel Avenues of Cancer Therapy

The global menace of cancer has led to an increased death toll in recent years. The constant evolution of cancer therapeutics with novel delivery systems has paved the way for translation of innovative therapeutics from bench to bedside. This review explains the significance of mesoporous silica nanoparticles (MSNs) as delivery vehicles with particular emphasis on cancer therapy, including novel opportunities for biomimetic therapeutics and vaccine delivery. Parameters governing MSN synthesis, therapeutic agent loading characteristics, along with tuning of MSN toward cancer cell specificity have been explained. The advent of MSN in nanotheranostics and its potential in forming nanocomposites for imaging purposes have been illustrated. Additionally, various hurdles encountered during the bench to bedside translation have been explained along with potential avenues to circumvent them. This also opens up new horizons in drug delivery, which could be useful to researchers in the years to come.

A Comparative Study of PMETAC-Modified Mesoporous Silica and Titania Thin Films for Molecular Transport Manipulation

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both mesoporous silica and mesoporous titania thin films. Pores were proven to be filled using ellipsometry and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Furthermore, the employed method leads to a polymer overlayer, whose thickness could be discriminated using a double-layer ellipsometry model. Cyclic voltammetry experiments reveal that the transport of electrochemically active probes is affected by the PMETAC presence, both due to the polymer overlayer and the confined charge of the pore-tethered PMETAC. A more detailed study demonstrates that ion permeability depends on the combined role of the inorganic scaffolds' (titania and silica) surface chemistry and the steric and charge exclusion properties of the polyelectrolyte. Interestingly, highly charged negative walls with positively charged polymers may resemble zwitterionic polymer behavior in confined environments.

Protein Condensation at Nanopore Entrances as Studied by Differential Scanning Calorimetry and Small-Angle Neutron Scattering

The condensation of globular myoglobin (Mb) at the pore entrances of mesoporous silica (MPS) with a series of pore diameters (4.2, 6.4, 7.7, and 9.0 nm) was examined by differential scanning calorimetry (DSC) and contrast-matching small-angle neutron scattering (CM-SANS) experiments. The DSC measurements were performed to estimate the amount of Mb adsorbed at two different adsorption sites, namely, the pore interior and the pore entrance regions. The CM-SANS measurements were conducted to observe condensation of Mb molecules at the pore entrance regions. Notably, the nanopore entrance with a diameter close to twice that of the Mb diameter was found to be the specific cavity to facilitate the condensation of globular Mb. The Mb condensation occurred at the entrances of the 6.4 nm pore during the adsorption uptake from concentrated Mb solutions, whereas the adsorption uptake from diluted Mb solutions induced the condensation of Mb at the entrances of the 7.7 nm pore.

Pushing the limits of nanopore transport performance by polymer functionalization

Inspired by the design and performance of biological pores, polymer functionalization of nanopores has emerged as an evolving field to advance transport performance within the last few years. This feature article outlines developments in nanopore functionalization and the resulting transport performance including gating based on electrostatic interaction, wettability and ligand binding, gradual transport controlled by polymerization as well as functionalization-based asymmetric nanopore and nanoporous material design going towards the transport direction. Pushing the limits of nanopore transport performance and thus reducing the performance gap between biological and technological pores is strongly related to advances in polymerization chemistry and their translation into nanopore functionalization. Thereby, the effect of the spatial confinement has to be considered for polymer functionalization as well as for transport regulation, and mechanistic understanding is strongly increased by combining experiment and theory. A full mechanistic understanding together with highly precise nanopore structure design and polymer functionalization is not only expected to improve existing application of nanoporous materials but also opens the door to new technologies. The latter might include out of equilibrium devices, ionic circuits, or machine learning based sensors.

Smart Strategies for Precise Delivery of CRISPR/Cas9 in Genome Editing

The emergence of CRISPR/Cas technology has enabled scientists to precisely edit genomic DNA sequences. This approach can be used to modulate gene expression for the treatment of genetic disorders and incurable diseases such as cancer. This potent genome-editing tool is based on a single guide RNA (sgRNA) strand that recognizes the targeted DNA, plus a Cas nuclease protein for binding and processing the target. CRISPR/Cas has great potential for editing many genes in different types of cells and organisms both in vitro and in vivo. Despite these remarkable advances, the risk of off-target effects has hindered the translation of CRISPR/Cas technology into clinical applications. To overcome this hurdle, researchers have devised gene regulatory systems that can be controlled in a spatiotemporal manner, by designing special sgRNA, Cas, and CRISPR/Cas delivery vehicles that are responsive to different stimuli, such as temperature, light, magnetic fields, ultrasound (US), pH, redox, and enzymatic activity. These systems can even respond to dual or multiple stimuli simultaneously, thereby providing superior spatial and temporal control over CRISPR/Cas gene editing. Herein, we summarize the latest advances on smart sgRNA, Cas, and CRISPR/Cas nanocarriers, categorized according to their stimulus type (physical, chemical, or biological).

Mesoporous Silica Nanoparticles in Chemical Detection: From Small Species to Large Bio-Molecules

A recompilation of applications of mesoporous silica nanoparticles in sensing from the last five years is presented. Its high potential, especially as hybrid materials combined with organic or bio-molecules, is shown. Adding to the multiplying effect of loading high amounts of the transducer into the pores, the selectivity attained by the interaction of the analyte with the layer decorating the material is described. Examples of the different methodologies are presented.

Mesoporous thin films on graphene FETs: nanofiltered, amplified and extended field-effect sensing

The ionic screening and the response of non-specific molecules are great challenges of biosensors based on field-effect transistors (FETs). In this work, we report the construction of graphene based transistors modified with mesoporous silica thin films (MTF-GFETs) and the unique (bio)sensing properties that arise from their synergy. The developed method allows the preparation of mesoporous thin films free of fissures, with an easily tunable thickness, and prepared on graphene-surfaces, preserving their electronic properties. The MTF-GFETs show good sensing capacity to small probes that diffuse inside the mesopores and reach the graphene semiconductor channel such as H⁺, OH^-, dopamine and H₂O₂. Interestingly, MTF-GFETs display a greater electrostatic gating response in terms of amplitude and sensing range compared to bare-GFETs for charged macromolecules that infiltrate the pores. For example, for polyelectrolytes and proteins of low MW, the amplitude increases almost 100% and the sensing range extends more than one order of magnitude. Moreover, these devices show a size-excluded electrostatic gating response given by the pore size. These features are even displayed at physiological ionic strength. Finally, a developed thermodynamic model evidences that the amplification and extended field-effect properties arise from the decrease of free ions inside the MTFs due to the entropy loss of confining ions in the mesopores. Our results demonstrate that the synergistic coupling of mesoporous films with FETs leads to nanofiltered, amplified and extended field-effect sensing (NAExFES).

Development of Amino Acids Functionalized SBA-15 for the Improvement of Protein Adsorption

Ordered mesoporous materials and their modification with multiple functional groups are of wide scientific interest for many applications involving interaction with biological systems and biomolecules (e.g., catalysis, separation, sensor design, nano-science or drug delivery). In particular, the immobilization of enzymes onto solid supports is highly attractive for industry and synthetic chemistry, as it allows the development of stable and cheap biocatalysts. In this context, we developed novel silylated amino acid derivatives (Si-AA-NH₂) that have been immobilized onto SBA-15 materials in biocompatible conditions avoiding the use of toxic catalyst, solvents or reagents. The resulting amino acid-functionalized materials (SBA-15@AA) were characterized by XRD, TGA, EA, Zeta potential, nitrogen sorption and FT-IR. Differences of the physical properties (e.g., charges) were observed while the structural ones remained unchanged. The adsorption of the enzyme lysozyme (Lyz) onto the resulting functionalized SBA-15@AA materials was evaluated at different pHs. The presence of different functional groups compared with bare SBA-15 showed better adsorption results, for example, 79.6 nmol of Lyz adsorbed per m² of SBA-15@Tyr compared with the 44.9 nmol/m² of the bare SBA-15.

Structural Characterization of Proteins Adsorbed at Nanoporous Materials

A nanoporous material has been applied for the development of functional nanobiomaterials by utilizing its uniform pore structure and large adsorption capacity. The structure and stability of biomacromolecules, such as peptide, oligonucleotide, and protein, are primary factors to govern the performance of nanobiomaterials, so that their direct characterization methodologies are in progress. In this review, we focus on recent topics in the structural characterization of protein molecules adsorbed at a nanoporous material with uniform meso-sized pores. The thermal stabilities of the adsorbed proteins are also summarized to discuss whether the structure of the adsorbed protein molecules can be stabilized or not.

PEG-PEI-modified gated N-doped mesoporous carbon nanospheres for pH/NIR light-triggered drug release and cancer phototherapy

A novel hybrid drug carrier has been designed, taking N-doped mesoporous carbon (NMCS) as the core and PEG-PEI as the outer shell. NMCS was functionalized with a photocleavable nitrobenzyl-based linker following a click reaction. Gemcitabine was loaded into NMCS prior to the functionalization via π-π stacking interactions. NIR and the pH-responsive behavior of NMCS-linker-PEG-PEI bestow the multifunctional drug carrier with the controlled release of gemcitabine triggered by dual stimuli. The NMCS core upconverts NIR light to UV, which is absorbed by a photosensitive molecular gate and results in its cleavage and drug release. Further, NMCS converts NIR to heat, which deforms the outside polymer shell, thus triggering the drug release process. The release can be promptly arrested if the NIR source is switched off. A promising gemcitabine release of 75% has been achieved within 24 h under the dual stimuli of pH and temperature. NMCS-linker-PEG-PEI produced reactive oxygen species (ROS), which were verified in FaDu cells using flow cytometry. In vitro experiments showed that the NMCS-linker-PEG-PEI-GEM hybrid particle can induce synergistic therapeutic effects in FADU cells when exposed to the NIR light.

Recent advances in the design of inorganic and nano-clay particles for the treatment of brain disorders

Inorganic materials, in particular nanoclays and silica nanoparticles, have attracted enormous attention due to their versatile and tuneable properties, making them ideal candidates for a wide range of biomedical applications, such as drug delivery. This review aims at overviewing recent developments of inorganic nanoparticles (like porous or mesoporous silica particles) and different nano-clay materials (like montmorillonite, laponites or halloysite nanotubes) employed for overcoming the blood brain barrier (BBB) in the treatment and therapy of major brain diseases such as Alzheimer's, Parkinson's, glioma or amyotrophic lateral sclerosis. Recent strategies of crossing the BBB through invasive and not invasive administration routes by using different types of nanoparticles compared to nano-clays and inorganic particles are overviewed.

Conjugated Polymer Nanoparticles Based on Copper Coordination for Real-Time Monitoring of pH-Responsive Drug Delivery

Metal coordination-driven composite systems have excellent stability and pH-responsive ability, making them suitable for specific drug delivery in physiological conditions. In this study, an anionic conjugated polymer PPEIDA with a poly(p-phenylene ethynylene) backbone and iminodiacetic acid (IDA) side chains is used as a drug carrier to construct a class of pH-responsive nanoparticles, PPEIDA-Cu-DOX conjugated polymer nanoparticles (CPNs), by taking advantage of the metal coordination interaction of Cu²⁺ with PPEIDA and the drug doxorubicin (DOX). PPEIDA-Cu-DOX CPNs have high drug loading and encapsulation efficiency (EE), calculated to be 54.30 ± 1.10 and 95.80 ± 0.84%, respectively. Due to the good spectral overlap, Förster resonance energy transfer (FRET) takes place between PPEIDA and the drug DOX, which enables the observation of the loading and the release of DOX from CPNs in an acidic environment by monitoring fluorescence emission changes. Therefore, PPEIDA-Cu-DOX CPNs can also be used in real-time cell imaging to monitor drug release in addition to delivering DOX targeting tumor cells. Compared with free DOX, PPEIDA-Cu-DOX CPNs show a similar inhibition to tumor cells and lower toxicity to normal cells. Our results demonstrate the feasibility and potential of constructing pH-responsive CPNs via metal-ligand coordination interactions for cancer treatment.

Aptamer-Functionalized Micro- and Nanocarriers for Controlled Release

Sequence-specific nucleic acids recognizing low-molecular-weight ligands or macromolecules (aptamers) have found growing interest for biomedical applications. The present review article summarizes recent applications of aptamers as stimuli-responsive gating units of drug (or dye)-loaded nano- or microcarriers for controlled and targeted drug release. In the presence of cellular biomarkers, the nano-/microcarriers are unlocked by forming aptamer-ligand complexes. Different aptamer-functinalized nano-/microcarriers are presented, including inorganic nanomaterials, metal-organic framework nanoparticles, and soft materials. The chemistries associated with the preparation of the carriers and the mechanisms to unlock the carriers are discussed. Stimuli-responsive gated drug-loaded micro-/nanocarriers hold great promise as functional sense-and-treat materials for the targeted and selective release of drugs.

Orienting the Pore Morphology of Core-Shell Magnetic Mesoporous Silica with the Sol-Gel Temperature. Influence on MRI and Magnetic Hyperthermia Properties

The controlled design of robust, well reproducible, and functional nanomaterials made according to simple processes is of key importance to envision future applications. In the field of porous materials, tuning nanoparticle features such as specific area, pore size and morphology by adjusting simple parameters such as pH, temperature or solvent is highly needed. In this work, we address the tunable control of the pore morphology of mesoporous silica (MS) nanoparticles (NPs) with the sol-gel reaction temperature (T_sg). We show that the pore morphology of MS NPs alone or of MS shell covering iron oxide nanoparticles (IO NPs) can be easily tailored with T_sg orienting either towards stellar (ST) morphology (large radial pore of around 10 nm) below 80 °C or towards a worm-like (WL) morphology (small randomly oriented pores channel network, of 3–4 nm pore size) above 80 °C. The relaxometric and magnetothermal features of IO@STMS or IO@WLMS core shell NPs having respectively stellar or worm-like morphologies are compared and discussed to understand the role of the pore structure for MRI and magnetic hyperthermia applications.

Porous Graphene Oxide Films Prepared via the Breath-Figure Method: A Simple Strategy for Switching Access of Redox Species to an Electrode Surface

Porous materials can be modified with physical barriers to control the transport of ions and molecules through channels via an external stimulus. Such capability has brought attention toward drug delivery, separation methods, nanofluidics, and point-of-care devices. In this context, gated platforms on which access to an electrode surface of species in solution can be reversibly hindered/unhindered on demand are appearing as promising materials for sensing and microfluidic switches. The preparation of a reversible gated device usually requires mesoporous materials, nanopores, or molecularly imprinted polymers. Here, we show how the breath-figure method assembly of graphene oxide can be used as a simple strategy to produce gated electrochemical materials. This was achieved by forming an organized porous thin film of graphene oxide onto an ITO surface. Localized brushes of thermoresponsive poly(N-isopropylacrylamide) were then grown to specific sites of the porous film by in situ reversible addition-fragmentation chain-transfer polymerization. The gating mechanism relies on the polymeric chains to expand and contract depending on the thermal stimulus, thus modulating the accessibility of redox species inside the pores. The resulting platform was shown to reversibly hinder or facilitate the electron transfer of solution redox species by modulating temperature from the room value to 45 °C or vice versa.

Remote Activation of Hollow Nanoreactors for Heterogeneous Photocatalysis in Biorelevant Media

Major current challenges in nano-biotechnology and nano-biomedicine include the implementation of predesigned chemical reactions in biological environments. In this context, heterogeneous catalysis is emerging as a promising approach to extend the richness of organic chemistry onto the complex environments inherent to living systems. Herein we report the design and synthesis of hybrid heterogeneous catalysts capable of being remotely activated by near-infrared (NIR) light for the performance of selective photocatalytic chemical transformations in biological media. This strategy is based on the synergistic integration of Au and TiO₂ nanoparticles within mesoporous hollow silica capsules, thus permitting an efficient hot-electron injection from the metal to the semiconductor within the interior of the capsule that leads to a confined production of reactive oxygen species. These hybrid materials can also work as smart NIR-responsive nanoreactors inside living mammalian cells, a cutting-edge advance toward the development of photoresponsive theranostic platforms.

Keeping It Together: Structures, Functions, and Applications of Viral Decoration Proteins

Decoration proteins are viral accessory gene products that adorn the surfaces of some phages and viral capsids, particularly tailed dsDNA phages. These proteins often play a "cementing" role, reinforcing capsids against accumulating internal pressure due to genome packaging, or environmental insults such as extremes of temperature or pH. Many decoration proteins serve alternative functions, including target cell recognition, participation in viral assembly, capsid size determination, or modulation of host gene expression. Examples that currently have structures characterized to high-resolution fall into five main folding motifs: β-tulip, β-tadpole, OB-fold, Ig-like, and a rare knotted α-helical fold. Most of these folding motifs have structure homologs in virus and target cell proteins, suggesting horizontal gene transfer was important in their evolution. Oligomerization states of decoration proteins range from monomers to trimers, with the latter most typical. Decoration proteins bind to a variety of loci on capsids that include icosahedral 2-, 3-, and 5-fold symmetry axes, as well as pseudo-symmetry sites. These binding sites often correspond to "weak points" on the capsid lattice. Because of their unique abilities to bind virus surfaces noncovalently, decoration proteins are increasingly exploited for technology, with uses including phage display, viral functionalization, vaccination, and improved nanoparticle design for imaging and drug delivery. These applications will undoubtedly benefit from further advances in our understanding of these versatile augmenters of viral functions.

Real-Time In Vivo Detection of Cellular Senescence through the Controlled Release of the NIR Fluorescent Dye Nile Blue

In vivo detection of cellular senescence is accomplished by using mesoporous silica nanoparticles loaded with the NIR-FDA approved Nile blue (NB) dye and capped with a galactohexasaccharide (S3). NB emission at 672 nm is highly quenched inside S3, yet a remarkable emission enhancement is observed upon cap hydrolysis in the presence of β-galactosidase and dye release. The efficacy of the probe to detect cellular senescence is tested in vitro in melanoma SK-Mel-103 and breast cancer 4T1 cells and in vivo in palbociclib-treated BALB/cByJ mice bearing breast cancer tumor.

Electro-responsive films containing voltage responsive gated mesoporous silica nanoparticles grafted onto PEDOT-based conducting polymer

The characteristics and electromechanical properties of conductive polymers together to their biocompatibility have boosted their application as a suitable tool in regenerative medicine and tissue engineering. However, conducting polymers as drug release materials are far from being ideal. A possibility to overcome this drawback is to combine conducting polymers with on-command delivery particles with inherent high-loading capacity. In this scenario, we report here the preparation of conduction polymers containing gated mesoporous silica nanoparticles (MSN) loaded with a cargo that is delivered on command by electro-chemical stimuli increasing the potential use of conducting polymers as controlled delivery systems. MSNs are loaded with Rhodamine B (Rh B), anchored to the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)], functionalized with a bipyridinium derivative and pores are capped with heparin (P3) by electrostatic interactions. P3 releases the entrapped cargo after the application of -640 mV voltage versus the saturated calomel electrode (SCE). Pore opening in the nanoparticles and dye delivery is ascribed to both (i) the reduction of the grafted bipyridinium derivative and (ii) the polarization of the conducting polymer electrode to negative potentials that induce detachment of positively charged heparin from the surface of the nanoparticles. Biocompatibility and cargo release studies were carried out in HeLa cells cultures.

An Adjustable pH-Responsive Drug Delivery System Based on Self-Assembly Polypeptide-Modified Mesoporous Silica

In this study, an adjustable pH-responsive drug delivery system using mesoporous silica nanoparticles (MSNs) as the host materials and the modified polypeptides as the nanovalves is reported. Since the polypeptide can self-assemble via electrostatic interaction at pH 7.4 and be disassembled by pH changes, the modified poly(l-lysine) and poly(l-glutamate) are utilized for pore blocking and opening in the study. Poly(l-lysine)-MSN (PLL-MSN) and poly(l-glutamate)-MSN (PLG-MSN) are synthesized via the ring opening polymerization of N-carboxyanhydrides onto the surface of mesoporous silica nanoparticles. The successful modification of the polypeptide on MSN is proved by Zeta potential change, X-ray photoelectron spectroscopy (XPS), solid state NMR, and MALDI-TOF MS. In vitro simulated dye release studies show that PLL-MSN and PLG-MSN can successfully load the dye molecules. The release study shows that the controlled release can be constructed at different pH by adjusting the ratio of PLL-MSN to PLG-MSN. Cellular uptake study indicates that the drug is detected in both cytoplasm and nucleus, especially in the nucleus. In vitro cytotoxicity assay indicates that DOX loaded mixture nanoparticles (ratio of PLL-MSN to PLG-MSN is 1:1) can be triggered for drug release in HeLa cells, resulting in 88% of cell killing.

Wetting-Controlled Localized Placement of Surface Functionalities within Nanopores

In the context of sensing and transport control, nanopores play an essential role. Designing multifunctional nanopores and placing multiple surface functionalities with nanoscale precision remains challenging. Interface effects together with a combination of different materials are used to obtain local multifunctionalization of nanoscale pores within a model pore system prepared by colloidal templating. Silica inverse colloidal monolayers are first functionalized with a gold layer to create a hybrid porous architecture with two distinct gold nanostructures on the top surface as well as at the pore bottom. Using orthogonal silane- and thiol-based chemistry together with a control of the wetting state allows individual addressing of the different locations within each pore resulting in nanoscale localized functional placement of three different functional units. Ring-opening metathesis polymerization is used for inner silica-pore wall functionalization. The hydrophobized pores create a Cassie-Baxter wetting state with aqueous solutions of thiols, which enables an exclusive functionalization of the outer gold structures. In a third step, an ethanolic solution able to wet the pores is used to self-assemble a thiol-containing initiator at the pore bottom. Subsequent controlled radical polymerization provides functionalization of the pore bottom. It is demonstrated that the combination of orthogonal surface chemistry and controlled wetting states can be used for the localized functionalization of porous materials.

Light-Induced Polymer Response through Thermoplasmonics Transduction in Highly Monodisperse Core-Shell-Brush Nanosystems

Smart nanosystems that transduce external stimuli to physical changes are an inspiring challenge in current materials chemistry. Hybrid organic-inorganic materials attract great attention due to the combination of building blocks responsive to specific external solicitations. In this work, we present a sequential method for obtaining an integrated core-shell-brush nanosystem that transduces light irradiation into a particle size change through a thermoplasmonic effect. We first synthesize hybrid monodisperse systems made up of functionalized silica colloids covered with controllable thermoresponsive poly(N-isopropylacrylamide), PNIPAm, brushes, produced through radical photopolymerization. This methodology was successfully transferred to Au@SiO₂ nanoparticles, leading to a core-shell-brush architecture, in which the Au core acts as a nanosource of heat; the silica layer, in turn, adapts the metal and polymer interfacial chemistries and can also host a fluorescent dye for bioimaging. Upon green LED irradiation, a light-to-heat conversion process leads to the shrinkage of the external polymer layer, as proven by in situ DLS. Our results demonstrate that modular hybrid nanosystems can be designed and produced with photothermo-physical transduction. These remote-controlled nanosystems present prospective applications in smart carriers, responsive bioscaffolds, or soft robotics.

Enteric pH responsive cargo release from PDA and PEG coated mesoporous silica nanoparticles: a comparative study in Drosophila melanogaster

Physiological stimulus-specific cargo release from nanoparticle carriers is a holy grail of drug delivery research. While the majority of such work is carried out in vitro with cell lines, widespread use of common mammalian model systems – mice and rats – is difficult due to the associated cost and regulatory restrictions. Here we use the inexpensive, easily reared, excellent genetic model system Drosophila melanogaster to test pH responsive cargo release from widely used mesoporous silica nanoparticles (MSNs) coated with pH sensitive polydopamine (PDA) and polyethylene glycol (PEG) polymers. We synthesized 650 ± 75 nm diameter PDA or PEG coated mesoporous silica nanoparticles loaded with a fluorescent dye and fed to individual adult flies. Subsequently, the passage of the particles were monitored through the fly gut. As in mammals, the fly intestine has multiple pH specific zones that are easily accessible for imaging and also genetic, biochemical or physiological manipulations. We observed that both the species of MSNs ruptured around the acidic (pH < 4.0) middle midgut of the flies. PEG coated particles showed sharper specificity of release in the acidic middle midgut of flies than the PDA coated ones and had less tendency to clump together. Our results clearly show that the Drosophila gut can be used as a model to test pH responsive biocompatible materials in vivo. Our work paves the way for greater use of Drosophila as an in vivo complete systemic model in drug delivery and smart materials research. It also suggests that such specific delivery of chemical/biological cargo can be exploited to study basic biology of the gut cells and their communication with other organs.

Targeted delivery in Drosophila middle mid-gut at pH < 4.0.

Multicompartmental Mesoporous Silica/Polymer Nanostructured Hybrids: Design Capabilities by Integrating Linear and Star-Shaped Block Copolymers

Poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP-b-PEO) linear diblock copolymer and polystyrene-poly(ethylene oxide) (PS10PEO10) heteroarm star copolymer were used as building elements to prepare organic-inorganic hybrids. By using the layer-by-layer (LbL) methodology, these elements were integrated on mesoporous silica through non-covalent interactions, namely, ionic and H-bonding. For the latter, tannic acid (TA) was used as an intermediate layer. The deposition of the various layers was monitored by thermogravimetric analysis (TGA), electrophoretic measurements, and confocal microscopy. The final silica hybrid, bearing alternating P2VP-b-PEO and PS10PEO10 star layers was capable of carrying one hydrophilic and two hydrophobic chemical species in distinct compartments. These multicompartmental organic-inorganic hybrids could be used as nanostructured carriers for pH-responsive multiple drug delivery and potential theranostic applications.

Hydrophobicity-responsive engineered mesoporous silica nanoparticles: application in the delivery of essential nutrients to bacteria combating oil spills

Facile chemical modification of mesoporous silica particles allows the production of gated reservoir systems capable of hydrophobicity-triggered release. Applied to the delivery of nutrients specifically to an oil phase, the systems developed have been shown to reliably assist the bacterial degradation of hydrocarbons. The gated system developed, made of C₁₈ hydrocarbon chains, is demonstrated to be in a closed collapsed state in an aqueous environment, yet opens up through solvation by lipophilic alkanes and releases its content on contact with the oil phase.

Chemical Stability of Mesoporous Oxide Thin Film Electrodes under Electrochemical Cycling: from Dissolution to Stabilization

Mesoporous oxide thin films (MOTF) present very high surface areas and highly controlled monodisperse pores in the nanometer range. These features spurred their possible applications in separation membranes and permselective electrodes. However, their performance in real applications is limited by their reactivity. Here, we perform a basic study of the stability of MOTF toward dissolution in aqueous media using a variety of characterization techniques. In particular, we focus in their stability behavior under the influence of ionic strength, adsorption of electrochemical probes, and applied electrode potential. Mesoporous silica thin films present a limited chemical stability after electrochemical cycling, particularly under high ionic strength, due to their high specific surface area and the interactions between the electrochemical probes and the surface. In contrast, TiO₂ or Si_0.9Zr_0.1O₂ matrices present higher stability; thus, they are an adequate alternative to produce accessible, sensitive, and robust permselective electrodes or membranes that perform under a wide variety of conditions.

A NIR-triggered gatekeeper of supramolecular conjugated unimicelles with two-photon absorption for controlled drug release

Near-infrared-sensitive supramolecular hyperbranched conjugated unimicelles were constructed for controlled drug release via two-photon excited fluorescence resonance energy transfer.

Cyclic iRGD peptide as a dual-functional on–off gatekeeper of mesoporous nanocontainers for targeting NRP-1 and selective drug release triggered by conformational conversion

A cyclic iRGD peptide as a dual-functional on–off gatekeeper on the surface of MSNs is prepared for specific NRP-1 targeting and selective drug release by conformational conversion.

Specific HER2 targeting and triggered drug release by conformational transformation of a dual-functional peptide gatekeeper on mesoporous nanocontainers

For specific targeting of HER2 and triggered drug release by stimuli-responsive conformational transformation, we developed a dual-functional cyclic peptide gatekeeper containing a HER2-binding sequence on the surface of mesoporous nanocontainers.

Mesoporous Bioactive Glasses Equipped with Stimuli-Responsive Molecular Gates for Controlled Delivery of Levofloxacin against Bacteria

An increase of bone diseases incidence has boosted the study of ceramic biomaterials as potential osteo-inductive scaffolds. In particular, mesoporous bioactive glasses have demonstrated to possess a broad application in the bone regeneration field, due their osteo-regenerative capability and their ability to release drugs from the mesoporous structure. These special features have been studied as an option to fight against bone infection, which is one of the most common problems regarding bone regeneration therapies. In this work, a mesoporous bioglass functionalized with polyamines and capped with adenosine triphosphate (ATP) as the molecular gate was developed for the controlled release of the antibiotic levofloxacin. Phosphate bonds of ATP were hydrolyzed in the presence of acid phosphatase (APase), the concentration of which is significantly increased in bone infection due to the activation of bone resorption processes. The solid was characterized and tested successfully against bacteria. The final gated solid induced bacterial death only in the presence of acid phosphatase. Additionally, it was demonstrated that the solid is not toxic against human cells. The double function of the prepared material as a drug delivery system and bone regeneration enhancer confirms the possible development of a new approach in the tissue engineering field, in which controlled release of therapeutic agents can be finely tuned and, at the same time, osteoinduction is favored.

In Vivo Examination of Folic Acid-Conjugated Gold-Silica Nanohybrids as Contrast Agents for Localized Tumor Diagnosis and Biodistribution

Enhanced biocompatibility of nanosized contrast agent with high radiodensity and specific biodistribution is an important parameter for localized tumor imaging and organ safety. Various nanoparticles, especially gold nanorods (GNRs), have been applied for tumor diagnosis. However, their toxicity, nonspecific biodistribution, and easy aggregation are critical issues in cancer medicine. To avoid these issues, encapsulation of the GNRs in the core of nanoscopic mesoporous silica (MS) under ambient conditions, yielding multifunctional nanomaterials for cancer nanomedicine, is a recent and active development. Interestingly, GNR embedded MS nanohybrid (GNR-MS), though a promising material in nanomedicine, is rarely examined for tumor diagnosis, in vivo toxicity, organ safety, contrast ability, and excretion. Herein, we report a systematic in vivo examination of folic acid functionalized GNR-MS (GNR-MS-FA) for localized 4T1 breast tumor diagnosis, organ safety, and excretion using a one-time dose administration. The nanomaterials show good aqueous dispersibility, biocompatibility, high radiodensity, and tumor specific targeting ability ( in vitro as well as in vivo). The in vivo tumor diagnosis and specific biodistribution of injected nanomaterials clearly demonstrates their potential for the visualization of tumors deep in the body of mice. In addition, all organs including the healthy glomerulus of the kidney are observed to be free of tissue injuries thereby indicating the superior biocompatibility of the nanomaterials.