Bionanotechnology based on silica nanoparticles

Optimization of ultrasound heating with Pickering droplets using core-shell scattering theory

Nanoparticles find widespread application in various medical contexts, including targeted nanomedicine and enhancing therapeutic efficacy. Moreover, they are employed to stabilize emulsions, giving rise to stabilized droplets known as Pickering droplets. Among the various methods to improve anti-cancer treatment, ultrasound hyperthermia stands out as an efficient approach. This research proposes Pickering droplets as promising sonosensitizer candidates, to enhance the attenuation of ultrasound with simultaneous potential to act as drug carriers. The enhanced ultrasound energy dissipation could be, therefore, optimized by changing the parameters of Pickering droplets. The ultrasound scattering theory, based on the core-shell model, was employed to calculate theoretical ultrasound properties such as attenuation and velocity. Additionally, computer simulations, based on a bioheat transfer model, were utilized to compute heat generation in agar-based phantoms of tissues under different ultrasound wave frequencies. Two types of phantoms were simulated: a pure agar phantom and an agar phantom incorporating spherical inclusions. The spherical inclusions, with a diameter of 10 mm, were doped with various sizes of Pickering droplets, considering their core radius and shell thickness. Computer simulation of these spherical inclusions incorporated within agar phantom resulted in different enhancement of achieved temperature elevation, which depending on the core radius, shell thickness, and the material properties of the system. Notably, spherical inclusions doped with Pickering droplets stabilized by magnetite nanoparticles exhibited a higher temperature rise compared to droplets stabilized by silica nanoparticles. Moreover, nanodroplets with a core radius below 400 nm demonstrated better heating performance compared to microdroplets. Furthermore, Pickering droplets incorporated into agar phantom could allow obtaining a similar effect of local heating as sophisticated focused ultrasound devices.

Water and ions in electrified silica nano-pores: a molecular dynamics study

Solid-liquid interfaces (SLIs) are ubiquitous in science and technology from the development of energy storage devices to the chemical reactions occurring in the biological milieu. In systems involving aqueous saline solutions as the liquid, both the water and the ions are routinely exposed to an electric field, whether the field is externally applied, or originating from the natural surface charges of the solid. In the current study a molecular dynamics (MD) framework is developed to study the effect of an applied voltage on the behaviour of ionic solutions located in a ∼7 nm pore between two uncharged hydrophilic silica slabs. We systematically investigate the dielectric properties of the solution and the organisation of the water and ions as a function of salt concentration. In pure water, the interplay between interfacial hydrogen bonds and the applied field can induce a significant reorganisation of the water orientation and densification at the interface. In saline solutions, at low concentrations and voltages the interface dominates the whole system due to the extended Debye length resulting in a dielectric constant lower than that for the bulk solution. An increase in salt concentration or voltage brings about more localized interfacial effects resulting in dielectric properties closer to that of the bulk solution. This suggests the possibility of tailoring the system to achieve the desired dielectric properties. For example, at a specific salt concentration, interfacial effects can locally increase the dielectric constant, something that could be exploited for energy storage.

Impact of the Crystal Structure of Silica Nanoparticles on Rhodamine 6G Adsorption: A Molecular Dynamics Study

Understanding the mechanism of adsorption of Rhodamine 6G (R6G) to various crystal structures of silica nanoparticles (SNPs) is important to elucidate the impact of dye size when measuring the size of the dye-SNP complex via the time-resolved fluorescence anisotropy method. In this work, molecular dynamics (MD) simulations were used to get an insight into the R6G adsorption process, which cannot be observed using experimental methods. It was found that at low pH, α-Cristobalite structured SNPs have a strong affinity to R6G; however, at high pH, more surface silanol groups undergo ionization when compared with α-Quartz, preventing the adsorption. Therefore, α-Quartz structured SNPs are more suitable for R6G adsorption at high pH than the α-Cristobalite ones. Furthermore, it was found that stable adsorption can occur only when the R6G xanthene core is oriented flat with respect to the SNP surface, indicating that the dye size does not contribute significantly to the measured size of the dye-SNP complex. The requirement of correct dipole moment orientation indicates that only one R6G molecule can adsorb on any sized SNP, and the R6G layer formation on SNP is not possible. Moreover, the dimerization process of R6G and its competition with the adsorption has been explored. It has been shown that the highest stable R6G aggregate is a dimer, and in this form, R6G does not adsorb to SNPs. Finally, using steered molecular dynamics (SMD) with constant-velocity pulling, the binding energies of R6G dimers and R6G complexes with both α-Quartz and α-Cristobalite SNPs of 40 Å diameter were estimated. These confirm that R6G adsorption is most stable on 40 Å α-Quartz at pH 7, although dimerization is equally possible.

Inorganic nanoparticles in dermopharmaceutical and cosmetic products: Properties, formulation development, toxicity, and regulatory issues

The use of nanotechnology strategies is a current hot topic, and research in this field has been growing significantly in the cosmetics industry. Inorganic nanoparticles stand out in this context for their distinctive physicochemical properties, leading in particular to an increased refractive index and absorption capacity giving them a broad potential for cutaneous applications and making them of special interest in research for dermopharmaceutical and cosmetic purposes. This performance is responsible for its heavy inclusion in the manufacture of skin health products such as sunscreens, lotions, beauty creams, skin ointments, makeup, and others. In particular, their suitable bandgap energy characteristics allow them to be used as photocatalytic semiconductors. They provide excellent UV absorption, commonly known as UV filters, and are responsible for their wide worldwide use in sunscreen formulations without the undesirable white residue after consumer application. In addition, cosmetics based on inorganic nanoparticles have several additional characteristics relevant to formulation development, such as being less expensive compared to other nanomaterials, having greater stability, and ensuring less irritation, itching, and propensity for skin allergies. This review will address in detail the main inorganic nanoparticles used in dermopharmaceutical and cosmetic products, such as titanium dioxide, zinc oxide, silicon dioxide, silver, gold, copper, and aluminum nanoparticles, nanocrystals, and quantum dots, reporting their physicochemical characteristics, but also their additional intrinsic properties that contribute to their use in this type of formulations. Safety issues regarding inorganic nanoparticles, based on toxicity studies, both to humans and the environment, as well as regulatory affairs associated with their use in dermopharmaceuticals and cosmetics, will be addressed.

Three in-one fenestrated approaches of yolk-shell, silver-silica nanoparticles: A comparative study of antibacterial, antifungal and anti-cancerous applications

Yolk-shell-based silica-coated silver nanoparticles are prominently used in the biomedical field aas well as bare silver nanoparticles for various biological applications. The present work narrates the synthesis and silica coating of metallic silver nanoparticles and investigates their antibacterial, antifungal, and anticancerous activity. Both synthesized nanoparticles were characterized by TEM, and SEM-EDX. The average size of silver nanoparticles was 50 nm, while after coating with silica, the average size of silica-coated silver nanoparticles was 80 nm. The nanoparticles' antibacterial, antifungal, and anticancer properties were comparatively examined in vitro. Agar well diffusion method was employed to explore the antibacterial activity against gram-positive bacteria (Bacillus cereus) and gram-negative bacteria (Escherichia coli) at different concentrations and antifungal activity against Candida Albicans. To understand the minimum concentration of both nanoparticles, we employed the minimum inhibitory concentration (MIC) test, against bacterial and fungal strains, which was dose dependent. We learned that bare silver nanoparticles showed high antibacterial activity, whereas silica-coated silver nanoparticles surpassed their antifungal capability over bare silver nanoparticles against Candida albicans. The anticancer activity of the as-prepared nanoparticles was executed in opposition to the prostate cancer cell (PC-3) line by MTT assay, which showed meaningful activity. Following this, flow cytometry was also effectuated to learn about the number of apoptotic and necrotic cells. The results of this study demonstrate the dynamic anti-cancerous, antibacterial, and antifungal activities of bare silver nanoparticles and silica-coated silver nanoparticles for a long-lasting period.

Developing of SiO2 Nanoshells Loaded with Fluticasone Propionate for Potential Nasal Drug Delivery: Determination of Pro-Inflammatory Cytokines through mRNA Expression

Mesoporous Silica Nanoparticles (MSN) are porous inorganic materials that have been extensively used for drug delivery due to their special qualities, such as biocompatibility, biodegradability, and non-toxicity. MSN is a promising drug delivery system to enhance the efficacy and safety of drug administration in nasal diseases like chronic rhinitis (CR). In this study, we used the sol-gel technique for MSN synthesis and incorporate fluticasone propionate (FP) for intranasal drug administration for the treatment of chronic rhinitis (CR). In order to confirm the particle size, shape, drug release, and compatibility, various instruments were used. MSN was effectively prepared with average sizes ranging between 400 ± 34 nm (mean ± SD) as measured by dynamic light scattering (DLS), while zeta potential verified in all cases their positive charged surface. To investigate MSN features, the Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), thermal analysis, X-ray diffraction (XRD), and nitrogen adsorption/desorption measurement were used. The loaded compound was submitted to in vitro dissolution tests, and a remarkable dissolution rate improvement was observed compared to the crystalline drug in both pH conditions (1.2 and 7.4 pH). By using an MTT assay cell viability was assessed. The expression levels of the anti-inflammatory cytokines IL-4 and IL-5 were also measured using mRNA extraction from rat blood. Other characterizations like acute toxicity and hemolytic activity were also performed to confirm loaded MSN safety. Loaded MSN was incorporated in nasal spray prepared by using innovator excipients including poloxamer. After this, its nasal spray's physical characteristics were also determined and compared with a commercial product (Ticovate).

Lateral flow assays for viruses diagnosis: Up-to-date technology and future prospects

Bacteria, viruses, and parasites are harmful microorganisms that cause infectious diseases. Early detection of diseases is critical to prevent disease transmission and provide epidemic preparedness, as these can cause widespread deaths and public health crises, particularly in resource-limited countries. Lateral flow assay (LFA) systems are simple-to-use, disposable, inexpensive diagnostic devices to test biomarkers in blood and urine samples. Thus, LFA has recently received significant attention, especially during the pandemic. Here, first of all, the design principles and working mechanisms of existing LFA methods are examined. Then, current LFA implementation strategies are presented for communicable disease diagnoses, including COVID-19, zika and dengue, HIV, hepatitis, influenza, malaria, and other pathogens. Furthermore, this review focuses on an overview of current problems and accessible solutions in detecting infectious agents and diseases by LFA, focusing on increasing sensitivity with various detection methods. In addition, future trends in LFA-based diagnostics are envisioned.

Partitional Behavior of Janus Dumbbell Microparticles in a Polyethylene Glycol (PEG)-Dextran (DEX) Aqueous Two-Phase System (ATPS)

Janus particles are known to be useful to various fields such as biomolecule-probing sensors, reaction catalysts, surfactants, and so on. They have two chemically different surfaces which possess contradictory characteristics such as polarity, hydrophobicity, etc. Here, a simple fabrication of dumbbell-shaped Janus microparticles was tested by the chemical reaction of carboxyl groups and amino groups to form amide bonds. They were distributed to the interface between polyethylene glycol (PEG)-rich phase and dextran (DEX)-rich phase, while the unreacted particles having carboxyl groups located at the top PEG-rich phase and particles having amine ligands went to the bottom DEX-rich phase of an aqueous two-phase system (ATPS). The fabrication procedures, observations, and possible applications of results are discussed.

Stealthy nanoparticles protect endothelial barrier from leakiness by resisting the absorption of VE-cadherin

Nanomaterial induced endothelial cell leakiness (NanoEL) is caused because nanomaterials enter the interstitial space of the endothelial cells and disrupt the endothelial cell-cell interactions by interacting with vascular endothelial cadherin (VE-cad). Whereas the NanoEL effect could cause controllable leakiness in cancer therapy, the gaps created by the NanoEL effect can make the cancer cells cross the endothelial barrier and produce side effects induced by using nanomedicine. In this paper, a series of ultralow protein corona nanoparticle is reported that can penetrate the endothelial cell junction without obviously interacting with the VE-cad and phosphorylating the tyrosine 658 (Y658) and tyrosine 731 (Y731) residues on VE-cad, thus preventing the VE-cad from being activated by Src kinase, and this avoids inducing of the NanoEL effect and cancer cell migration, regardless of particle material, density and surface charge. These findings provide a new idea for the design of novel nanoparticles without side effects and can maximize their cancer-killing effect.

Emerging Applications of Nanotechnology in Healthcare Systems: Grand Challenges and Perspectives

Healthcare, as a basic human right, has often become the focus of the development of innovative technologies. Technological progress has significantly contributed to the provision of high-quality, on-time, acceptable, and affordable healthcare. Advancements in nanoscience have led to the emergence of a new generation of nanostructures. Each of them has a unique set of properties that account for their astonishing applications. Since its inception, nanotechnology has continuously affected healthcare and has exerted a tremendous influence on its transformation, contributing to better outcomes. In the last two decades, the world has seen nanotechnology taking steps towards its omnipresence and the process has been accelerated by extensive research in various healthcare sectors. The inclusion of nanotechnology and its allied nanocarriers/nanosystems in medicine is known as nanomedicine, a field that has brought about numerous benefits in disease prevention, diagnosis, and treatment. Various nanosystems have been found to be better candidates for theranostic purposes, in contrast to conventional ones. This review paper will shed light on medically significant nanosystems, as well as their applications and limitations in areas such as gene therapy, targeted drug delivery, and in the treatment of cancer and various genetic diseases. Although nanotechnology holds immense potential, it is yet to be exploited. More efforts need to be directed to overcome these limitations and make full use of its potential in order to revolutionize the healthcare sector in near future.

Engineering of magnetic nanoparticles as magnetic particle imaging tracers

Magnetic particle imaging (MPI) has recently emerged as a promising non-invasive imaging technique because of its signal linearly propotional to the tracer mass, ability to generate positive contrast, low tissue background, unlimited tissue penetration depth, and lack of ionizing radiation. The sensitivity and resolution of MPI are highly dependent on the properties of magnetic nanoparticles (MNPs), and extensive research efforts have been focused on the design and synthesis of tracers. This review examines parameters that dictate the performance of MNPs, including size, shape, composition, surface property, crystallinity, the surrounding environment, and aggregation state to provide guidance for engineering MPI tracers with better performance. Finally, we discuss applications of MPI imaging and its challenges and perspectives in clinical translation.

Silica and graphene mediate arsenic detection in mature rice grain by a newly patterned current-volt aptasensor

Arsenic is a major global threat to the ecosystem. Here we describe a highly accurate sensing platform using silica nanoparticles/graphene at the surface of aluminum interdigitated electrodes (Al IDE), able to detect trace amounts of arsenic(III) in rice grain samples. The morphology and electrical properties of fabricated Al IDEs were characterized and standardized using AFM, and SEM with EDX analyses. Micrometer scale Al IDEs were fabricated with silicon, aluminum, and oxygen as primary elements. Validation of the bare Al IDE with electrolyte fouling was performed at different pH levels. The sensing surface was stable with no electrolyte fouling at pH 7. Each chemical modification step was monitored with current-volt measurement. The surface chemical bonds were characterized by fourier transform infrared spectroscopy (FTIR) and revealed different peaks when interacting with arsenic (1600-1000 cm^-1). Both silica nanoparticles and graphene presented a sensitive limit of detection as measured by slope calibration curves at 0.0000001 pg/ml, respectively. Further, linear regression was established using ΔI (A) = 3.86 E^-09 log (Arsenic concentration) [g/ml] + 8.67 E^-08 [A] for silica nanoparticles, whereas for graphene Y = 3.73 E^-09 (Arsenic concentration) [g/ml] + 8.52 E^-08 on the linear range of 0.0000001 pg/ml to 0.01 pg/ml. The R² for silica (0.96) and that of graphene (0.94) was close to the maximum (1). Modification with silica nanoparticles was highly stable. The potential use of silica nanoparticles in the detection of arsenic in rice grain extract can be attributed to their size and stability.

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening

A simple fluorescence-based lateral flow test platform for rapid influenza B virus screening as a model target molecule was successfully developed. In this work, Cy5-loaded silica nanoparticles were directly conjugated to monoclonal antibodies, specific to the influenza B nucleoprotein, via a direct physisorption method and used as detector probes. Using this approach, the signal response to the detection was further determined using a fluorescent signal intensity measurement method via a portable reader, in combination with fluorescence imaging analysis. The degree to which the fluorescence signal response is detected is proportional to the amount of the target virus protein present in the system, reflected by the accumulation of the formed particle-antibody conjugates within the test system. Under optimized conditions, the system is capable of detecting the influenza B virus protein at a level of 0.55 μg per test within 30 min, using small sample volumes as low as 100 μL (R² = 0.9544). In addition to its simplicity, further application of the system in detecting the influenza B virus protein was demonstrated using the viral transport media as specimen matrices. It was also shown that the system can perform the detection without cross-reactivity to other closely related respiratory viruses.

[Preparation of luminescent silica nanoparticles with immobilized metal ion affinity for labeling phosphorylated proteins in Western Blot]

Protein phosphorylation is an important type of post-translational protein modification. In Western Blot experiment, the assay of phosphoproteins need special phospho antibodies, which are expensive, difficult to preserve, poorly reproducible. To this end, the immobilized metal ion affinity luminescent silica nanoparticles for instead of phospho antibodies were prepared. A layer of polymer was created on the surface of the silica nanoparticles via co-polymerization to protect the nanoparticles and to functionalize them with the immobilized metal ion affinity property to specifically label the phosphorylated proteins in Western Blot assays. The affinity luminescent silica nanoparticles were prepared with the following procedure. First, the sol-gel precursor fluorescein isothiocyanate-3-aminopropyltriethoxysilane (FITC-APTES) with the fluorescent moiety was prepared by modifying APTES with FITC. The luminescent silica nanoparticles (FITC@SiO₂) were synthesized using the Stöber synthesis method in a reversed microemulsion. Briefly, 123.2 mL of cyclohexane, 25.6 mL of n-hexanol, and 5.44 mL of deionized water were ultrasonically mixed, and then 28.3 g of Triton X-100 were added and the mixture was magnetically stirred for 15 min to form a clear and transparent microemulsion system. Within 10 min, 0.8 mL of FITC-APTES precursor, 1.6 mL of tetraethoxysilane (TEOS), and 0.96 mL of concentrated ammonia (25%-27%, mass fraction) were added to the microemulsion, and the mixture was stirred at 24 ℃ for 24 h. After the reaction, the microemulsion system was destroyed by adding 200 mL of ethanol. The resulting FITC@SiO₂ luminescent silica nanoparticles were centrifuged, and washed three times with ethanol. After dryness, the FITC@SiO₂ nanoparticles were modified with methacryloxy-propyltrimethoxysilane (MPS) to introduce the double bonds for further modification. The functional monomer nitrilotriacetic acid (NTA) and glycidyl methacrylate (GMA) were copolymerized on the surface of the nanoparticles to convert FITC@SiO₂-MPS to FITC@SiO₂-MPS-GMA-NTA. The polymer coating of the silica nanoparticles was not only able to protect the silica from hydrolysis, but also to introduce the functional groups of nitrilotriacetic acid, which can chelate with metal ions. Elemental analysis demonstrated that the NTA groups had been bonded to the surface of the nanoparticles via copolymerization. The polymerization did not affect the morphology and fluorescence properties of the nanoparticles. The FITC@SiO₂-MPS-GMA-NTA nanoparticles were activated with three different metal ions Zr⁴⁺, Fe³⁺, and Ti⁴⁺, for the enrichment of phosphorylated peptides derived form α-casein tryptic digestion. HPLC-MS analysis indicated that the FITC@SiO₂-MPS-GMA-NTA-Ti ⁴⁺ nanoparticles are the best for the enrichment of phosphorylated peptides. The FITC@SiO₂-MPS-GMA-NTA-Ti⁴⁺ nanoparticles were used for labelling the phosphorylated proteins in Western Blot experiment. The electrophoretic band of α-casein could be clearly labeled with the FITC@SiO₂-MPS-GMA-NTA-Ti ⁴⁺ nanoparticles, while the bovine albumin band could not be labelled. This indicates that the luminescent FITC@SiO₂-MPS-GMA-NTA-Ti⁴⁺nanoparticles can be used to label the phosphorylated proteins in Western Blot experiments.

Recent developments in stimuli responsive nanomaterials and their bionanotechnology applications

Bionanotechnology is an ever-expanding field as innovations in nanotechnology continue to be developed based on biological systems or to be applied to address unmet needs in biology, biomedicine, etc., including various sensor and drug delivery solutions. Amidst the wide range of bionanomaterials that have been developed, stimuli responsive bionanomaterials are of particular interest and are thus emphasized within this review. Here, we have highlighted the most recent advances for stimuli responsive bionanomaterials with focus on those possessing responses based on activation, expansion/contraction and self-assembly/disassembly. The aim of this review is to bring attention to some of the most current bionanotechnology research and the interesting applications within this field.

Physics Comes to the Aid of Medicine-Clinically-Relevant Microorganisms through the Eyes of Atomic Force Microscope

Despite the hope that was raised with the implementation of antibiotics to the treatment of infections in medical practice, the initial enthusiasm has substantially faded due to increasing drug resistance in pathogenic microorganisms. Therefore, there is a need for novel analytical and diagnostic methods in order to extend our knowledge regarding the mode of action of the conventional and novel antimicrobial agents from a perspective of single microbial cells as well as their communities growing in infected sites, i.e., biofilms. In recent years, atomic force microscopy (AFM) has been mostly used to study different aspects of the pathophysiology of noninfectious conditions with attempts to characterize morphological and rheological properties of tissues, individual mammalian cells as well as their organelles and extracellular matrix, and cells’ mechanical changes upon exposure to different stimuli. At the same time, an ever-growing number of studies have demonstrated AFM as a valuable approach in studying microorganisms in regard to changes in their morphology and nanomechanical properties, e.g., stiffness in response to antimicrobial treatment or interaction with a substrate as well as the mechanisms behind their virulence. This review summarizes recent developments and the authors’ point of view on AFM-based evaluation of microorganisms’ response to applied antimicrobial treatment within a group of selected bacteria, fungi, and viruses. The AFM potential in development of modern diagnostic and therapeutic methods for combating of infections caused by drug-resistant bacterial strains is also discussed.

On the Role of Silica Carrier Curvature for the Unloading of Small Drug Molecules: A Molecular Dynamics Simulation Study

We present atomic scale models of differently shaped silica surfaces loaded by gemcitabine and ibuprofene molecules. Despite the dissimilar nature of the drug molecules, their association to silica carriers shows quite similar characteristics. We identify a well-defined contact layer that is stabilized by silica-molecule salt-bridges/hydrogen bonding in parallel to interactions among the drug molecules. Additional loading of the carriers leads to rough films with dynamically evolving asperities rather than layer-by-layer ordering. To elucidate the role of differently shaped silica surfaces, we compared planar slab models and spherical nanoparticles as 2 limiting cases. Despite the strong difference in the curvature of the silica surfaces, our molecular dynamics simulations show only small changes of the unloading characteristics. This suggests that the design of different pore shapes in mesoporous silica-based drug carriers mainly affects the migration kinetics rather than the energetics of drug loading and release.

Nanomedical detection and downstream analysis of circulating tumor cells in head and neck patients

The establishment of novel biomarkers in liquid biopsies of cancer patients has come more into focus in prognostic and diagnostic research efforts. Due to their prognostic relevance disseminated tumor cells or circulating tumor cells are the subject of intensive research and are discussed as early diagnostic indicators for treatment failure and the formation of micrometastases. A potential association of this early-systemic tumor component with poor prognosis of cancer patients could be already demonstrated for various entities including breast, colon, lung, melanoma, ovarian and prostate cancers. Thus, the detection of circulating tumor cells seems to be also applicable for minimal-invasive monitoring of therapy progress in head and neck cancer patients. A major problem of the use in clinical routine is that circulating tumor cells could not be detected by modern imaging techniques. To overcome these limitations highly sensitive detection methods and techniques for their molecular characterization are urgently needed allowing mechanistic understanding and targeting of circulating tumor cells. Especially the medical application of nanotechnology (nanomedical methods) has made valuable contributions to the field. Here, we want to provide a comprehensive overview on (nanomedical) detection methods for circulating tumor cells and discuss their merits, pitfalls and future perspectives especially for head and neck solid squamous cell carcinoma (HNSCC) patients.

Encapsulation for Cancer Therapy

The current rapid advancement of numerous nanotechnology tools is being employed in treatment of many terminal diseases such as cancer. Nanocapsules (NCs) containing an anti-cancer drug offer a very promising alternative to conventional treatments, mostly due to their targeted delivery and precise action, and thereby they can be used in distinct applications: as biosensors or in medical imaging, allowing for cancer detection as well as agents/carriers in targeted drug delivery. The possibility of using different systems-inorganic nanoparticles, dendrimers, proteins, polymeric micelles, liposomes, carbon nanotubes (CNTs), quantum dots (QDs), biopolymeric nanoparticles and their combinations-offers multiple benefits to early cancer detection as well as controlled drug delivery to specific locations. This review focused on the key and recent progress in the encapsulation of anticancer drugs that include methods of preparation, drug loading and drug release mechanism on the presented nanosystems. Furthermore, the future directions in applications of various nanoparticles are highlighted.

Determination of Surface Preference Using Heterospectral Surface-Bulk Correlation Spectroscopy

We outline a method by which the surface preference of a species in a multicomponent mixture may be obtained using surface-specific visible-infrared sum frequency generation (SFG) spectroscopy combined with bulk infrared absorption and/or Raman data. In general, the problem is complicated by the fact that the SFG signal is a function of both the surface coverage and the structure of the molecules. Two-dimensional correlation analysis can be used to reveal which spectral features are changing synchronously, that is, in phase with each other, and which ones are evolving in a manner that is phase-shifted by 90° (asynchronous correlation) as a function of the bulk composition. We provide a framework for determining the surface preference from the correlations between the vibrational modes in the SFG spectra and between the modes from SFG and bulk infrared and/or Raman spectra. When compared to the equivalent analysis performed using the SFG spectra alone, this method can be used with the data obtained using a single-beam polarization and in congested spectral regions where fitting to isolate the behavior of individual vibrational modes is not robust.

Carbon-nanotube reinforcement of DNA-silica nanocomposites yields programmable and cell-instructive biocoatings

Biomedical applications require substrata that allow for the grafting, colonization and control of eukaryotic cells. Currently available materials are often limited by insufficient possibilities for the integration of biological functions and means for tuning the mechanical properties. We report on tailorable nanocomposite materials in which silica nanoparticles are interwoven with carbon nanotubes by DNA polymerization. The modular, well controllable and scalable synthesis yields materials whose composition can be gradually adjusted to produce synergistic, non-linear mechanical stiffness and viscosity properties. The materials were exploited as substrata that outperform conventional culture surfaces in the ability to control cellular adhesion, proliferation and transmigration through the hydrogel matrix. The composite materials also enable the construction of layered cell architectures, the expansion of embryonic stem cells by simplified cultivation methods and the on-demand release of uniformly sized stem cell spheroids.

"Ghost" Silica Nanoparticles of "Host"-Inherited Antibacterial Action

We fabricated surface-rough mesoporous silica nanoparticles ("ghost" SiO₂NPs) by using composite mesoporous copper oxide nanoparticles ("host" CuONPs) as templates, which allowed us to mimic their surface morphology. The "host" CuONPs used here as templates, however, had a very high antibacterial effect, with or without functionalization. To evaluate the surface roughness effect on the "ghost" SiO₂NPs antibacterial action, we functionalized them with (3-glycidyloxypropyl)trimethoxysilane (GLYMO) to permit additional covalent coupling of 4-hydroxyphenylboronic acid (4-HPBA). The diol groups on the bacterial membrane can form reversible covalent bonds with boronic acid (BA) groups on the "ghost" SiO₂NPs surface and bind to the bacteria, resulting in a very strong amplification of their antibacterial activity, which does not depend on electrostatic adhesion. The BA-functionalized "ghost" SiO₂NPs showed a very significant antibacterial effect as compared to smooth SiO₂NPs of the same surface coating and particle size. We attribute this to the "ghost" SiO₂NPs mesoporous surface morphology, which mimics to a certain extent those of the original mesoporous CuONPs used as templates for their preparation. We envisage that the "ghost" SiO₂NPs effectively acquire some of the antibacterial properties from the "host" CuONPs, with the same functionality, despite being completely free of copper. The antibacterial effect of the functionalized "ghost" SiO₂NPs/GLYMO/4-HPBA on Rhodococcus rhodochrous (R. rhodochrous) and Escherichia coli (E. coli) is much higher than that of the nonfunctionalized "ghost" SiO₂NPs or the "ghost" SiO₂NPs/GLYMO. The results indicate that the combination of rough surface morphology and strong adhesion of the particle surface to the bacteria can make even benign material such as silica act as a strong antimicrobial agent. Additionally, our BA-functionalized nanoparticles ("ghost" SiO₂NPs/GLYMO/4-HPBA) showed no detectable cytotoxic impact against human keratinocytes at particle concentrations, which are effective against bacteria.

Naturally Occurring and Synthetic Mesoporous Nanosilica: Multimodal Applications in Frontier Areas of Science

Mesoporous silica nanoparticles (MSNs) have gained attention worldwide due to their structural versatility for diverse applications in a number of frontier areas of sciences. The intrinsic chemical, textural and structural features of MSNs allow fabricating versatile multifunctional nanosystems. The present review provides an overview of the research progress in artificial and biological production of MSNs, their properties and various applications in cutting edge areas of sciences.

Microwave Assisted Sol-Gel Synthesis of Silica-Spider Silk Composites

This study introduces a simple and environmentally friendly method to synthesize silica-protein nanocomposite materials using microwave energy to solubilize hydrophobic protein in an aqueous solution of pre-hydrolyzed organo- or fluoro-silane. Sol-gel functionality can be enhanced through biomacromolecule incorporation to tune mechanical properties, surface energy, and biocompatibility. Here, synthetic spider silk protein and organo- and fluoro-silane precursors were dissolved and mixed in weakly acidic aqueous solution using microwave technology. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) images revealed the formation of spherical nanoparticles with sizes ranging from 100 to 500 nm depending, in part, on silane fluoro- or organo-side chain chemistry. The silane-protein interaction in the nanocomposite was assessed through infrared spectroscopy. Deconvoluted ATR-FTIR (Attenuated total reflectance Fourier-transform infrared spectroscopy) spectra revealed silane chemistry-specific conformational changes in the protein-silane nanocomposites. Relative to microwave-solubilized spider silk protein, the β structure content increased by 14% in the spider silk-organo-silica nanocomposites, but decreased by a net 20% in the spider silk-fluoro-silica nanocomposites. Methods of tuning the secondary structures, and in particular β-sheets that are the cross-linking moieties in spider silks and other self-assembling fibrillar proteins, may provide a unique means to promote protein interactions, favor subsequent epitaxial growth process, and enhance the properties of the protein-silane nanocomposites.

Biopebble Containers: DNA-Directed Surface Assembly of Mesoporous Silica Nanoparticles for Cell Studies

The development of methods for colloidal self-assembly on solid surfaces is important for many applications in biomedical sciences. Toward this goal, described is a versatile class of mesoporous silica nanoparticles (MSN) that contain on their surface various types of DNA molecules to enable their self-assembly into micropatterned surface architectures useful for cell studies. Monodisperse dye-doped MSN are synthesized by biphase stratification and functionalized with an aptamer oligonucleotide that serves as gatekeeper for the triggered release of encapsulated molecular cargo, such as fluorescent dye rhodamine B or the anticancer drug doxorubicin. One or two additional types of oligonucleotides are installed on the MSN surface to enable DNA-directed immobilization on solid substrates bearing patterns of complementary capture oligonucleotides. It is demonstrated that this strategy can be used for efficient self-assembly of microstructured surface architectures, which not only promote the adhesion and guidance of cells but also are capable of affecting the fate of adhered cells through triggered release of their cargo. It is believed that this approach is useful for diverse applications in tissue engineering and nanobio sciences.

Molecular mechanisms of mesoporous silica formation from colloid solution: Ripening-reactions arrest hollow network structures

The agglomeration of silica nanoparticles in aqueous solution is investigated from molecular simulations. Mimicking destabilization of colloidal solutions by full removal of protective moieties or surface charge, association of SiO₂/Si(OH)₄ core/shell particles leads to rapid proton transfer reactions that account for local silanole → silica ripening reactions. Yet, such virtually barrier-less binding is only observed within a limited contact zone. Agglomeration hence leads to the formation of oligomers of nanoparticles, whilst full merging into a compact precipitate is hampered by the need for extended structural reorganisation. Implementing sufficiently fast supply from colloidal solution, our simulations show the development of silica networks comprised of covalently bound, yet not fully merged nanoparticles. Within the oligomerized nanoparticle network, coordination numbers range from 2 to 5 –which is far below closest packing. Our simulations hence rationalize the formation of covalently bound network structures hosting extended pores. The resulting interfaces to the solvent show water immobilization only for the immediate contact layers, whilst the inner pores exhibit solvent mobility akin to bulk water.

Tobacco Mosaic Virus-Functionalized Mesoporous Silica Nanoparticles, a Wool-Ball-like Nanostructure for Drug Delivery

The design of versatile tools to improve cell targeting and drug delivery in medicine has become increasingly pertinent to nanobiotechnology. Biological and inorganic nanocarrier drug delivery systems are being explored, showing advantages and disadvantages in terms of cell targeting and specificity, cell internalization, efficient payload delivery, and safety profiles. Combining the properties of a biological coating on top of an inorganic nanocarrier, we hypothesize that this hybrid system would improve nanoparticle-cell interactions, resulting in enhanced cell targeting and uptake properties compared to the bare inorganic nanocarrier. Toward this goal, we engineered a hierarchical assembly featuring the functionalization of cargo-loaded mesoporous silica nanoparticles (MSNPs) with tobacco mosaic virus (TMV) as a biological coating. The MSNP functions as a delivery system because the porous structure enables high therapeutic payload capacity, and TMV serves as a biocompatible coating to enhance cell interactions. The resulting MSNP@TMV nanohybrids have a wool-ball-like appearance and demonstrate enhanced cell uptake, hence cargo delivery properties. The MSNP@TMV have potential for medical applications such as drug delivery, contrast agent imaging, and immunotherapy.

Heteroatom-doped core/shell carbonaceous framework materials: synthesis, characterization and electrochemical properties

Multiple heteroatom-doped core/shell carbonaceous framework materials showed a rapid charge–discharge capacity and excellent cycling stability, demonstrating great potential for anode materials for lithium ion batteries.

In vitro and in vivo accumulation of magnetic nanoporous silica nanoparticles on implant materials with different magnetic properties

Background

In orthopedic surgery, implant-associated infections are still a major problem. For the improvement of the selective therapy in the infection area, magnetic nanoparticles as drug carriers are promising when used in combination with magnetizable implants and an externally applied magnetic field. These implants principally increase the strength of the magnetic field resulting in an enhanced accumulation of the drug loaded particles in the target area and therewith a reduction of the needed amount and the risk of undesirable side effects. In the present study magnetic nanoporous silica core–shell nanoparticles, modified with fluorophores (fluorescein isothiocyanate/FITC or rhodamine B isothiocyanate/RITC) and poly(ethylene glycol) (PEG), were used in combination with metallic plates of different magnetic properties and with a magnetic field. In vitro and in vivo experiments were performed to investigate particle accumulation and retention and their biocompatibility.

Results

Spherical magnetic silica core–shell nanoparticles with reproducible superparamagnetic behavior and high porosity were synthesized. Based on in vitro proliferation and viability tests the modification with organic fluorophores and PEG led to highly biocompatible fluorescent particles, and good dispersibility. In a circular tube system martensitic steel 1.4112 showed superior accumulation and retention of the magnetic particles in comparison to ferritic steel 1.4521 and a Ti90Al6V4 control. In vivo tests in a mouse model where the nanoparticles were injected subcutaneously showed the good biocompatibility of the magnetic silica nanoparticles and their accumulation on the surface of a metallic plate, which had been implanted before, and in the surrounding tissue.

Conclusion

With their superparamagnetic properties and their high porosity, multifunctional magnetic nanoporous silica nanoparticles are ideal candidates as drug carriers. In combination with their good biocompatibility in vitro, they have ideal properties for an implant directed magnetic drug targeting. Missing adverse clinical and histological effects proved the good biocompatibility in vivo. Accumulation and retention of the nanoparticles could be influenced by the magnetic properties of the implanted plates; a remanent martensitic steel plate significantly improved both values in vitro. Therefore, the use of magnetizable implant materials in combination with the magnetic nanoparticles has promising potential for the selective treatment of implant-associated infections.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0422-6) contains supplementary material, which is available to authorized users.

The Dynamics of Nanoparticle-enhanced Fluid Displacement in Porous Media - A Pore-scale Study

This work provides new insights into the dynamics of silica nanoparticle-based removal of organic fluids (here oil) from naturally occurring porous media. We have used 4D (time-resolved 3D) imaging at pore-scale using X-ray computed micro-tomography (μCT) technique. The captured 3D tomographic time-series data reveal the dynamics of immiscible oil displacement from a carbonate rock upon injection of nanoparticle (NP) suspensions (0.06 and 0.12 wt% SiO₂ in deionised water). Our analysis shows significant pore-scale remobilisation of initially trapped oil upon injection of the NP suspensions, specifically, at higher concentration. Our data shows that oil clusters become significantly smaller with larger fluid/fluid interface as a result of the higher concentration NP injection. This paper demonstrates that use of 2D radiograms collected during fluid injections allows monitoring flow dynamics at time resolutions down to a few seconds using conventional laboratory-based μCT scanners. Here, as an underlying mechanism for oil remobilisation, we present the first 4D evidence of in-situ formation of an oil in water emulsion induced by nanoparticles.

Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring

The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine.

Detrimental impact of silica nanoparticles on the nanomechanical properties of Escherichia coli, studied by AFM

Despite great innovative and technological promises, nanoparticles (NPs) can ultimately exert an antibacterial activity by affecting the cell envelope integrity. This envelope, by conferring the cell its rigidity and protection, is intimately related to the mechanical behavior of the bacterial surface. Depending on their size, surface chemistry, shape, NPs can induce damages to the cell morphology and structure among others, and are therefore expected to alter the overall mechanical properties of bacteria. Although Atomic Force Microscopy (AFM) stands as a powerful tool to study biological systems, with high resolution and in near physiological environment, it has rarely been applied to investigate at the same time both morphological and mechanical degradations of bacteria upon NPs treatment. Consequently, this study aims at quantifying the impact of the silica NPs (SiO₂-NPs) on the mechanical properties of E. coli cells after their exposure, and relating it to their toxic activity under a critical diameter. Cell elasticity was calculated by fitting the force curves with the Hertz model, and was correlated with the morphological study. SiO₂-NPs of 100 nm diameter did not trigger any significant change in the Young modulus of E. coli, in agreement with the bacterial intact morphology and membrane structure. On the opposite, the 4 nm diameter SiO₂-NPs did induce a significant decrease in E. coli Young modulus, mainly associated with the disorganization of lipopolysaccharides in the outer membrane and the permeation of the underlying peptidoglycan layer. The subsequent toxic behavior of these NPs is finally confirmed by the presence of membrane residues, due to cell lysis, exhibiting typical adhesion features.

Brighter, More Stable, and Less Toxic: A Host-Guest Interaction-Aided Strategy for Fabricating Fluorescent Silica Nanoparticles and Applying Them in Bioimaging and Biosensing at the Cellular Level

The exploration of fluorescent tools with distinguished optical properties and favorable biocompatibility is significant for biosensing and bioimaging. We herein present a host-guest interactions aided strategy for fabricating fluorescent silica nanoparticles (FSNPs), which is enabled by cyclodextrin (CD) supermolecules. Compared with conventional FSNPs, the modified products (are named as fluorophore@CD@SNPs) possess several advantages. First, the incorporated fluorophores can thoroughly get rid of their intrinsic aggregation due to CD's inclusion effect, and the fluorescence intensity of the obtained fluorophore@CD@SNPs can enhance 48-67%. The fluorophores can then be well-fixed by the host CD molecules. As a result, the leak rates of the incorporated fluorophores are only 15-17%, which is about 3 times lower than that of conventional ones (42-48%). Notably, the as-prepared fluorophore@CD@SNPs show observable less cytotoxicity as compared with their conventional counterparts, probably due to the substantially decreased leakage of the incorporated fluorophores. Because of prominent properties and versatile fabrication, the proposed fluorophore@CD@SNPs not only possess better performances for cell-imaging but are competent for ratiometric sensing of pH value at living cell using (indicator-reference) integrative silica NPs.

Cellular pathways involved in silica nanoparticles induced apoptosis: A systematic review of in vitro studies

Silica nanoparticles (SiNPs) have been found to pass through biological barriers and get distributed in the human body. They induce cell apoptosis via various mechanisms in body organs. To understand these mechanisms, we carried out systematic review of in vitro studies on SiNPs-induced cell apoptosis. Office of Health Assessment and Translation approach for Systematic Review and Evidence Integration was used to identify 14 studies dating from the year 2000 to current. Four studies showed an increase in DNA damage, cell cycle arrest, proapoptotic factors and decrease in antiapoptotic factors resulting to apoptosis. Eight studies showed induction of mitochondrial dysfunction, Bax upregulation, Bcl-2 downregulation, and caspase-3, -7, -9 activities increase. Increase in FADD, TNFR1 and Bid proteins was observed in one study, while the other NO production and caspase-3 activity was increased. These studies found the potency of SiNPs to induce cell apoptosis through DNA damage, mitochondrial, tumor necrosis factor, and nitric oxide related pathways.

Diatom-Inspired Silica Nanostructure Coatings with Controllable Microroughness Using an Engineered Mussel Protein Glue to Accelerate Bone Growth on Titanium-Based Implants

Silica nanoparticles (SiNPs) have been utilized to construct bioactive nanostructures comprising surface topographic features and bioactivity that enhances the activity of bone cells onto titanium-based implants. However, there have been no previous attempts to create microrough surfaces based on SiNP nanostructures even though microroughness is established as a characteristic that provides beneficial effects in improving the biomechanical interlocking of titanium implants. Herein, a protein-based SiNP coating is proposed as an osteopromotive surface functionalization approach to create microroughness on titanium implant surfaces. A bioengineered recombinant mussel adhesive protein fused with a silica-precipitating R5 peptide (R5-MAP) enables direct control of the microroughness of the surface through the multilayer assembly of SiNP nanostructures under mild conditions. The assembled SiNP nanostructure significantly enhances the in vitro osteogenic cellular behaviors of preosteoblasts in a roughness-dependent manner and promotes the in vivo bone tissue formation on a titanium implant within a calvarial defect site. Thus, the R5-MAP-based SiNP nanostructure assembly could be practically applied to accelerate bone-tissue growth to improve the stability and prolong the lifetime of medical implantable devices.