Mesoporous Silica Materials as Drug Delivery: "The Nightmare" of Bacterial Infection

Antibiotic resistance and nanotechnology: A narrative review

The rise of antibiotic resistance poses a significant threat to public health worldwide, leading researchers to explore novel solutions to combat this growing problem. Nanotechnology, which involves manipulating materials at the nanoscale, has emerged as a promising avenue for developing novel strategies to combat antibiotic resistance. This cutting-edge technology has gained momentum in the medical field by offering a new approach to combating infectious diseases. Nanomaterial-based therapies hold significant potential in treating difficult bacterial infections by circumventing established drug resistance mechanisms. Moreover, their small size and unique physical properties enable them to effectively target biofilms, which are commonly linked to resistance development. By leveraging these advantages, nanomaterials present a viable solution to enhance the effectiveness of existing antibiotics or even create entirely new antibacterial mechanisms. This review article explores the current landscape of antibiotic resistance and underscores the pivotal role that nanotechnology plays in augmenting the efficacy of traditional antibiotics. Furthermore, it addresses the challenges and opportunities within the realm of nanotechnology for combating antibiotic resistance, while also outlining future research directions in this critical area. Overall, this comprehensive review articulates the potential of nanotechnology in addressing the urgent public health concern of antibiotic resistance, highlighting its transformative capabilities in healthcare.

Antifouling nanoplatform for controlled attachment ofE. coli

Biofouling is the most common cause of bacterial contamination in implanted materials/devices resulting in severe inflammation, implant mobilization, and eventual failure. Since bacterial attachment represents the initial step toward biofouling, developing synthetic surfaces that prevent bacterial adhesion is of keen interest in biomaterials research. In this study, we develop antifouling nanoplatforms that effectively impede bacterial adhesion and the consequent biofilm formation. We synthesize the antifouling nanoplatform by introducing silicon (Si)/silica nanoassemblies to the surface through ultrafast ionization of Si substrates. We assess the effectiveness of these nanoplatforms in inhibitingEscherichia coli(E. coli) adhesion. The findings reveal a significant reduction in bacterial attachment on the nanoplatform compared to untreated silicon, with bacteria forming smaller colonies. By manipulating physicochemical characteristics such as nanoassembly size/concentration and nanovoid size, we further control bacterial attachment. These findings suggest the potential of our synthesized nanoplatform in developing biomedical implants/devices with improved antifouling properties.

Synthesis and characterization of faujasite zeolite membrane for selective enrichment of Arthrobacter sp. in synthetic wastewater

This paper centers on the preparation and characterization of both a clay support and a faujasite zeolite membrane. Additionally, the study explores the development of bacterial media to assess the performance of these prepared membranes. The faujasite zeolite membrane was created using the hydrothermal method, involving the deposition of a faujasite layer to fine-tune the pore sizes of the clay support. The clay supports were crafted from clay which was sieved to particle size Φ ≤ 63 μm, and compacted with 3.0 wt.% activated carbon, then sintered at 1,000 °C. Distilled water fluxes revealed a decrease from 1,500 L m-2 h-1 to a minimum of 412 L m-2 h-1 after 180 min of filtration. Both membranes were characterized by XRF, XRD, FTIR, adsorption-desorption of nitrogen (N2), and SEM-EDS. PCR technique was used for the identification of the isolated Arthrobacter sp., and the retention of the bacteria on the clay support and the faujasite zeolite membrane were found to be 96 and 99%, respectively. The results showed that the faujasite zeolite membrane passed the clay support due to a narrow pore size of the faujasite zeolite membrane of 2.28 nm compared to 3.55 nm for the clay supports.

Antibiofilm activity of mesoporous silica nanoparticles against the biofilm associated infections

In pharmaceutical industries, various chemical carriers are present which are used for drug delivery to the correct target sites. The most popular and upcoming drug delivery carriers are mesoporous silica nanoparticles (MSN). The main reason for its popularity is its ability to be specific and optimize the drug delivery process in a controlled manner. Nowadays, MSNs are widely used to eradicate various microbial infections, especially the ones related to biofilms. Biofilms are sessile groups of cells that live by forming a consortium and exhibit antibacterial resistance (AMR). They exhibit AMR by extracellular polymeric substances (EPS) and various quorum sensing (QS) signaling molecules. Usually, bacterial and fungal cells are capable of forming biofilms. These biofilms are pathogenic. In the majority of the cases, biofilms cause nosocomial diseases. This review will focus on the antibiofilm activities of MSN, its mechanism of target-specific drug delivery, and its ability to disrupt the bacterial biofilms inhibiting the infection. The review will also discuss various mechanisms for the delivery of pharmaceutical molecules by the MSNs to inhibit the bacterial biofilms, and lastly, we will talk about the different types of MSNs and their antibiofilm activities.

Staphylococcus aureus epidemiology, pathophysiology, clinical manifestations and application of nano-therapeutics as a promising approach to combat methicillin resistant Staphylococcus aureus

Staphylococcus aureus is a Gram-positive bacterium and one of the most prevalent infectious disease-related causes of morbidity and mortality in adults. This pathogen can trigger a broad spectrum of diseases, from sepsis and pneumonia to severe skin infections that can be fatal. In this review, we will provide an overview of S. aureus and discuss the extensive literature on epidemiology, transmission, genetic diversity, evolution and antibiotic resistance strains, particularly methicillin resistant S. aureus (MRSA). While many different virulence factors that S. aureus produces have been investigated as therapeutic targets, this review examines recent nanotechnology approaches, which employ materials with atomic or molecular dimensions and are being used to diagnose, treat, or eliminate the activity of S. aureus. Finally, having a deeper understanding and clearer grasp of the roles and contributions of S. aureus determinants, antibiotic resistance, and nanotechnology will aid us in developing anti-virulence strategies to combat the growing scarcity of effective antibiotics against S. aureus.

Exploring the Synergy between Nano-Formulated Linezolid and Polymyxin B as a Gram-Negative Effective Antibiotic Delivery System Based on Mesoporous Silica Nanoparticles

Antimicrobial resistance is a current silent pandemic that needs new types of antimicrobial agents different from the classic antibiotics that are known to lose efficiency over time. Encapsulation of antibiotics inside nano-delivery systems could be a promising, effective strategy that is able to delay the capability of pathogens to develop resistance mechanisms against antimicrobials. These systems can be adapted to deliver already discovered antibiotics to specific infection sites in a more successful way. Herein, mesoporous silica nanomaterials are used for an efficient delivery of a linezolid gram-positive antibiotic that acts synergistically with gram-negative antimicrobial polymyxin B. For this purpose, linezolid is encapsulated in the pores of the mesoporous silica, whose outer surface is coated with a polymyxin B membrane disruptor. The nanomaterial showed a good controlled-release performance in the presence of lipopolysaccharide, found in bacteria cell membranes, and the complete bacteria E. coli DH5α. The performed studies demonstrate that when the novel formulation is near bacteria, polymyxin B interacts with the cell membrane, thereby promoting its permeation. After this step, linezolid can easily penetrate the bacteria and act with efficacy to kill the microorganism. The nano-delivery system presents a highly increased antimicrobial efficacy against gram-negative bacteria, where the use of free linezolid is not effective, with a fractional inhibitory concentration index of 0.0063 for E. coli. Moreover, enhanced toxicity against gram-positive bacteria was confirmed thanks to the combination of both antibiotics in the same nanoparticles. Although this new nanomaterial should be further studied to reach clinical practice, the obtained results pave the way to the development of new nanoformulations which could help in the fight against bacterial infections.

Nanostructured N/S doped carbon dots/mesoporous silica nanoparticles and PVA composite hydrogel fabrication for anti-microbial and anti-biofilm application

Regarding the convergence of the worldwide epidemic, the appearance of bacterial infection has occasioned in a melodramatic upsurge in bacterial pathogens with confrontation against one or numerous antibiotics. The implementation of engineered nanostructured particles as a delivery vehicle for antimicrobial agent is one promising approach that could theoretically battle the setbacks mentioned. Among all nanoparticles, silica nanoparticles have been found to provide functional features that are advantageous for combatting bacterial contagion. Apart from that, carbon dots, a zero-dimension nanomaterial, have recently exhibited their photo-responsive property to generate reactive oxygen species facilitating to enhance microorganism suppression and inactivation ability. In this study, potentials of core/shell mesoporous silica nanostructures (MSN) in conjugation with carbon dots (CDs) toward antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli have been investigated. Nitrogen and sulfur doped CDs (NS/CDs) conjugated with MSN which were cost effective nanoparticles exhibited much superior antimicrobial activity for 4 times as much as silver nanoparticles against all bacteria tested. Among all nanoparticles tested, 0.40 M NS/CDs@MSN showed the greatest minimal biofilm inhibitory at very low concentration (< 0.125 mg mL-1), followed by 0.20 M NS/CDs@MSN (0.5 mg mL-1), CD@MSN (25 mg mL-1), and MSN (50 mg mL-1), respectively. Immobilization of NS/CDs@MSN in polyvinyl alcohol (PVA) hydrogel was performed and its effect on antimicrobial activity, biofilm controlling efficiency, and cytotoxicity toward fibroblast (NIH/3 T3 and L-929) cells was additionally studied for further biomedical applications. The results demonstrated that 0.40 M NS/CDs-MSN@PVA hydrogel exhibited the highest inhibitory effect on S. aureus > P. aeruginosa > E. coli. In addition, MTT assay revealed some degree of toxicity of 0.40 M NS/CDs-MSN@PVA hydrogel against L-929 cells by a slight reduction of cell viability from 100% to 81.6% when incubated in the extract from 0.40 M NS/CDs-MSN@PVA hydrogel, while no toxicity of the same hydrogel extract was detected toward NIH/3 T3 cells.

Organically Modified Mesoporous Silica Nanoparticles against Bacterial Resistance

Bacterial antimicrobial resistance is posed to become a major hazard to global health in the 21st century. An aggravating issue is the stalled antibiotic research pipeline, which requires the development of new therapeutic strategies to combat antibiotic-resistant infections. Nanotechnology has entered into this scenario bringing up the opportunity to use nanocarriers capable of transporting and delivering antimicrobials to the target site, overcoming bacterial resistant barriers. Among them, mesoporous silica nanoparticles (MSNs) are receiving growing attention due to their unique features, including large drug loading capacity, biocompatibility, tunable pore sizes and volumes, and functionalizable silanol-rich surface. This perspective article outlines the recent research advances in the design and development of organically modified MSNs to fight bacterial infections. First, a brief introduction to the different mechanisms of bacterial resistance is presented. Then, we review the recent scientific approaches to engineer multifunctional MSNs conceived as an assembly of inorganic and organic building blocks, against bacterial resistance. These elements include specific ligands to target planktonic bacteria, intracellular bacteria, or bacterial biofilm; stimuli-responsive entities to prevent antimicrobial cargo release before arriving at the target; imaging agents for diagnosis; additional constituents for synergistic combination antimicrobial therapies; and aims to improve the therapeutic outcomes. Finally, this manuscript addresses the current challenges and future perspectives on this hot research area.

Chelating silica nanoparticles for efficient antibiotic delivery and particle imaging in Gram-negative bacteria

The inefficacy of antibiotics against Gram-negative bacteria is a major challenge for treatment of many clinically important bacterial infections. The complex structure of the double cell membrane of Gram-negative bacteria makes it inaccessible to many key antibiotics such as vancomycin and also presents a major challenge for drug development. In this study we design of a novel hybrid silica nanoparticle system bearing membrane targeting groups with the antibiotic encapsulated together with a ruthenium luminescent tracking agent, for optical detection of the nanoparticle delivery in the bacterial cell. The hybrid system shows delivery of vancomycin and efficacy against a library of Gram negative bacterial species. Evidence of penetration of nanoparticles in bacteria cells is achieved via luminescence of the ruthenium signal. Our studies show that nanoparticles modified with aminopolycarboxylate chelating groups are an effective delivery system in bacterial growth inhibition in species whereas the molecular antibiotic is ineffective. This design provides a new platform for delivery of antibiotics that cannot alone penetrate the bacterial membrane.

Antibacterial and biofilm-inhibitory effects of vancomycin-loaded mesoporous silica nanoparticles on methicillin-resistant staphylococcus aureus and gram-negative bacteria

The present study aimed to prepare and characterize vancomycin-loaded mesoporous silica nanoparticles (Van-MSNs) to detect inhibitory effects on the planktonic and biofilm forms of methicillin-resistant Staphylococcus aureus (MRSA) isolates, and study the biocompatibility and toxicity of Van-MSNs in vitro as well as antibacterial activity of Van-MSNs against Gram-negative bacteria. The inhibitory effects of Van-MSNs were investigated on MRSA using the determination of minimum inhibitory (MIC) and minimum biofilm-inhibitory concentrations (MBIC) as well as the effect on bacterial attachment. Biocompatibility was studied by examining the effect of Van-MSNs on the lysis and sedimentation rate of red blood cells (RBC). The interaction of Van-MSNs with human blood plasma was detected by the SDS-PAGE approach. The cytotoxic effect of the Van-MSNs on human bone marrow mesenchymal stem cells (hBM-MSCs) was evaluated by the MTT assay. The antibacterial effects of vancomycin and Van-MSNs on Gram-negative bacteria were also investigated using MIC determination using the broth microdilution method. Furthermore, bacteria outer membrane (OM) permeabilization was determined. Van-MSNs showed inhibitory effects on planktonic and biofilm forms of bacteria on all isolates at levels lower than MICs and MBICs of free vancomycin, but the antibiofilm effect of Van-MSNs was not significant. However, Van-MSNs did not affect bacterial attachment to surfaces. Van-loaded MSNs did not show a considerable effect on the lysis and sedimentation of RBC. A low interaction of Van-MSNs was detected with albumin (66.5 kDa). The hBM-MSCs viability in exposure to different levels of Van-MSNs was 91-100%. MICs of ≥ 128 µg/mL were observed for vancomycin against all Gram-negative bacteria. In contrast, Van-MSNs exhibited modest antibacterial activity inhibiting the tested Gram-negative bacterial strains, at concentrations of ≤ 16 µg/mL. Van-MSNs increased the OM permeability of bacteria that can increase the antimicrobial effect of vancomycin. According to our findings, Van-loaded MSNs have low cytotoxicity, desirable biocompatibility, and antibacterial effects and can be an option for the battle against planktonic MRSA.

Surface Modification of Silica Particles with Adhesive Functional Groups or Their Coating with Chitosan to Improve the Retention of Toothpastes in the Mouth

Silica is widely used in the oral care formulations to act as an abrasive and to give the products its distinct physical properties. In this study, silica particles were synthesized using a co-condensation of tetraethyl orthosilicate with a series of functional silane compounds [(3-mercaptopropyl)trimethoxysilane, (3-glycidyloxypropyl)trimethoxysilane, and (3-acryloxypropyl)trimethoxysilane)]. The surface of the particles based on tetraethyl orthosilicate and (3-glycidyloxypropyl)trimethoxysilane was then further modified with 3-aminophenylboronic acid. Commercial Aerosil R972 Pharma silica particles were also coated with chitosan. Additionally, commercially available (3-maleimido)propyl-functionalized silica particles were used in this study. All these functionalized silica particles were incorporated into toothpaste formulations, and their retentive properties were tested on ex vivo sheep tongue mucosa models using fluorescent microscopy-based flow-through techniques. Those surfaces with chitosan, phenylboronic acid, and acryloyl groups were shown to provide a significant improvement in the retention of the oral care formulations during the retention testing. The retention of toothpastes containing silica functionalized with maleimide and thiol groups was also superior compared to that of unmodified silica particles. This study synthesized and tested a range of silica particles and demonstrated that the functionalized silica incorporated into toothpastes can significantly improve the retention of these formulations on oral mucosal surfaces.

Magneto-Fluorescent Mesoporous Nanocarriers for the Dual-Delivery of Ofloxacin and Doxorubicin to Tackle Opportunistic Bacterial Infections in Colorectal Cancer

Cancer-related opportunistic bacterial infections are one major barrier for successful clinical therapies, often correlated to the production of genotoxic factors and higher cancer incidence. Although dual anticancer and antimicrobial therapies are a growing therapeutic fashion, they still fall short when it comes to specific delivery and local action in in vivo systems. Nanoparticles are seen as potential therapeutic vectors, be it by means of their intrinsic antibacterial properties and effective delivery capacity, or by means of their repeatedly reported modulation and maneuverability. Herein we report on the production of a biocompatible, antimicrobial magneto-fluorescent nanosystem (NANO3) for the delivery of a dual doxorubicin-ofloxacin formulation against cancer-related bacterial infections. The drug delivery capacity, rendered by its mesoporous silica matrix, is confirmed by the high loading capacity and stimuli-driven release of both drugs, with preference for tumor-like acidic media. The pH-dependent emission of its surface fluorescent SiQDs, provides an insight into NANO3 surface behavior and pore availability, with the SiQDs working as pore gates. Hyperthermia induces heat generation to febrile temperatures, doubling drug release. NANO3-loaded systems demonstrate significant antimicrobial activity, specifically after the application of hyperthermia conditions. NANO3 structure and antimicrobial properties confirm their potential use in a future dual anticancer and antimicrobial therapeutical vector, due to their drug loading capacity and their surface availability for further modification with bioactive, targeting species.

Addressing a future pandemic: how can non-biological complex drugs prepare us for antimicrobial resistance threats?

Loss of effective antibiotics through antimicrobial resistance (AMR) is one of the greatest threats to human health. By 2050, the annual death rate resulting from AMR infections is predicted to have climbed from 1.27 million per annum in 2019, up to 10 million per annum. It is therefore imperative to preserve the effectiveness of both existing and future antibiotics, such that they continue to save lives. One way to conserve the use of existing antibiotics and build further contingency against resistant strains is to develop alternatives. Non-biological complex drugs (NBCDs) are an emerging class of therapeutics that show multi-mechanistic antimicrobial activity and hold great promise as next generation antimicrobial agents. We critically outline the focal advancements for each key material class, including antimicrobial polymer materials, carbon nanomaterials, and inorganic nanomaterials, and highlight the potential for the development of antimicrobial resistance against each class. Finally, we outline remaining challenges for their clinical translation, including the need for specific regulatory pathways to be established in order to allow for more efficient clinical approval and adoption of these new technologies.

Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area.

Fabrication of Rechargeable Photoactive Silk Fibroin/Polyvinyl Alcohol Blend Nanofibrous Membranes for Killing Bacteria

Antibacterial materials that prevent bacterial infections and mitigate bacterial virulence have attracted great scientific interest. In recent decades, bactericidal polymers have been presented as promising candidates to combat bacterial pathogens. However, the preparation of such materials has proven to be extremely challenging. Herein, photoactive silk fibroin/polyvinyl alcohol blended nanofibrous membranes grafted with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (G-SF/PVA BNM) were fabricated by an electrospinning technique. The premise of this work is that the G-SF/PVA BNM can store photoactive activity under light irradiation and release reactive oxygen species for killing bacteria under dark conditions. The results showed that the resultant G-SF/PVA BNM exhibited the integrated properties of an ultrathin fiber diameter (298 nm), good mechanical properties, robust photoactive activity and photo-store capacity, and great photoinduced antibacterial activity against E. coli and S. aureus (99.999% bacterial reduction with 120 min). The successful construction of blended nanofibrous membranes gives a new possibility to the design of highly efficient antibacterial materials for public health protection.

A pH-Gated Functionalized Hollow Mesoporous Silica Delivery System for Photodynamic Sterilization in Staphylococcus aureus Biofilm

Multidrug-resistant bacteria are increasing, particularly those embedded in microbial biofilm. These bacteria account for most microbial infections in humans. Traditional antibiotic treatment has low efficiency in sterilization of biofilm-associated pathogens, and thus the development of new approaches is highly desired. In this study, amino-modified hollow mesoporous silica nanoparticles (AHMSN) were synthesized and used as the carrier to load natural photosensitizer curcumin (Cur). Then glutaraldehyde (GA) and polyethyleneimine (PEI) were used to seal the porous structure of AHMSN by the Schiff base reaction, forming positively charged AHMSN@GA@PEI@Cur. The Cur delivery system can smoothly diffuse into the negatively charged biofilm of Staphylococcus aureus (S. aureus). Then Cur can be released to the biofilm after the pH-gated cleavage of the Schiff base bond in the slightly acidic environment of the biofilm. After the release of the photosensitizer, the biofilm was irradiated by the blue LED light at a wavelength of 450 nm and a power of 37.4 mV/cm² for 5 min. Compared with the control group, the number of viable bacteria in the biofilm was reduced by 98.20%. Therefore, the constructed pH-gated photosensitizer delivery system can efficiently target biofilm-associated pathogens and be used for photodynamic sterilization, without the production of antibiotic resistance.

Bacteria-Assisted Transport of Nanomaterials to Improve Drug Delivery in Cancer Therapy

Currently, the design of nanomaterials for the treatment of different pathologies is presenting a major impact on biomedical research. Thanks to this, nanoparticles represent a successful strategy for the delivery of high amounts of drugs for the treatment of cancer. Different nanosystems have been designed to combat this pathology. However, the poor penetration of these nanomaterials into the tumor tissue prevents the drug from entering the inner regions of the tumor. Some bacterial strains have self-propulsion and guiding capacity thanks to their flagella. They also have a preference to accumulate in certain tumor regions due to the presence of different chemo-attractants factors. Bioconjugation reactions allow the binding of nanoparticles in living systems, such as cells or bacteria, in a simple way. Therefore, bacteria are being used as a transport vehicle for nanoparticles, facilitating their penetration and the subsequent release of the drug inside the tumor. This review would summarize the literature on the anchoring methods of diverse nanosystems in bacteria and, interestingly, their advantages and possible applications in cancer therapy.

Characterization of the Antibacterial Activity of an SiO2 Nanoparticular Coating to Prevent Bacterial Contamination in Blood Products

Technological innovations and quality control processes within blood supply organizations have significantly improved blood safety for both donors and recipients. Nevertheless, the risk of transfusion-transmitted infection remains non-negligible. Applying a nanoparticular, antibacterial coating at the surface of medical devices is a promising strategy to prevent the spread of infections. In this study, we characterized the antibacterial activity of an SiO₂ nanoparticular coating (i.e., the “Medical Antibacterial and Antiadhesive Coating” [MAAC]) applied on relevant polymeric materials (PM) used in the biomedical field. Electron microscopy revealed a smoother surface for the MAAC-treated PM compared to the reference, suggesting antiadhesive properties. The antibacterial activity was tested against selected Gram-positive and Gram-negative bacteria in accordance with ISO 22196. Bacterial growth was significantly reduced for the MAAC-treated PVC, plasticized PVC, polyurethane and silicone (90–99.999%) in which antibacterial activity of ≥1 log reduction was reached for all bacterial strains tested. Cytotoxicity was evaluated following ISO 10993-5 guidelines and L929 cell viability was calculated at ≥90% in the presence of MAAC. This study demonstrates that the MAAC could prevent bacterial contamination as demonstrated by the ISO 22196 tests, while further work needs to be done to improve the coating processability and effectiveness of more complex matrices.

Superparamagnetic Iron Oxide Nanoparticles Decorated Mesoporous Silica Nanosystem for Combined Antibiofilm Therapy

A crucial challenge to face in the treatment of biofilm-associated infection is the ability of bacteria to develop resistance to traditional antimicrobial therapies based on the administration of antibiotics alone. This study aims to apply magnetic hyperthermia together with controlled antibiotic delivery from a unique magnetic-responsive nanocarrier for a combination therapy against biofilm. The design of the nanosystem is based on antibiotic-loaded mesoporous silica nanoparticles (MSNs) externally functionalized with a thermo-responsive polymer capping layer, and decorated in the outermost surface with superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs are able to generate heat upon application of an alternating magnetic field (AMF), reaching the temperature needed to induce a change in the polymer conformation from linear to globular, therefore triggering pore uncapping and the antibiotic cargo release. The microbiological assays indicated that exposure of E. coli biofilms to 200 µg/mL of the nanosystem and the application of an AMF (202 kHz, 30 mT) decreased the number of viable bacteria by 4 log10 units compared with the control. The results of the present study show that combined hyperthermia and antibiotic treatment is a promising approach for the effective management of biofilm-associated infections.

Arabic gum plus colistin coated moxifloxacin-loaded nanoparticles for the treatment of bone infection caused by Escherichia coli

Osteomyelitis is an inflammatory process of bone and bone marrow that may even lead to patient death. Even though this disease is mainly caused by Gram-positive organisms, the proportion of bone infections caused by Gram-negative bacteria, such as Escherichia coli, has significantly increased in recent years. In this work, mesoporous silica nanoparticles have been employed as platform to engineer a nanomedicine able to eradicate E. coli- related bone infections. For that purpose, the nanoparticles have been loaded with moxifloxacin and further functionalized with Arabic gum and colistin (AG+CO-coated MX-loaded MSNs). The nanosystem demonstrated high affinity toward E. coli biofilm matrix, thanks to AG coating, and marked antibacterial effect because of the bactericidal effect of moxifloxacin and the disaggregating effect of colistin. AG+CO-coated MX-loaded MSNs were able to eradicate the infection developed on a trabecular bone in vitro and showed pronounced antibacterial efficacy in vivo against an osteomyelitis provoked by E. coli. Furthermore, AG+CO-coated MX-loaded MSNs were shown to be essentially non-cytotoxic with only slight effect on cell proliferation and mild hepatotoxicity, which might be attributed to the nature of both antibiotics. In view of these results, these nanoparticles may be considered as a promising treatment for bone infections caused by enterobacteria, such as E. coli, and introduce a general strategy against bone infections based on the implementation of antibiotics with different but complementary activity into a single nanocarrier. STATEMENT OF SIGNIFICANCE: In this work, we propose a methodology to address E.coli bone infections by using moxifloxacin-loaded mesoporous silica nanoparticles coated with Arabic gum containing colistin (AG+CO-coated MX-loaded MSNs). The in vitro evaluation of this nanosystem demonstrated high affinity toward E. coli biofilm matrix thanks to the Arabic gum coating, a disaggregating and antibacterial effect of colistin, and a remarkable antibiofilm action because of the bactericidal ability of moxifloxacin and colistin. This anti-E. coli capacity of AG+CO-coated MX-loaded MSNs was brought out in an in vivo rabbit model of osteomyelitis where the nanosystem was able to eradicate more than 90% of the bacterial load within the infected bone.

Optical clearing of tissues: Issues of antimicrobial phototherapy and drug delivery

This review presents principles and novelties in the field of tissue optical clearing (TOC) technology, as well as application for optical monitoring of drug delivery and effective antimicrobial phototherapy. TOC is based on altering the optical properties of tissue through the introduction of immersion optical cleaning agents (OCA), which impregnate the tissue of interest. We also analyze various methods and kinetics of delivery of photodynamic agents, nanoantibiotics and their mixtures with OCAs into the tissue depth in the context of antimicrobial and antifungal phototherapy. In vitro and in vivo studies of antimicrobial phototherapies, such as photodynamic, photothermal plasmonic and photocatalytic, are summarized, and the prospects of a new TOC technology for effective killing of pathogens are discussed.

Chronology of Global Success: 20 Years of Prof Vallet-Regí Solving Questions

Twenty years ago, a group of bold scientists led by Prof Vallet-Regí suggested for the first time the use of mesoporous materials as potential drug delivery systems. Without knowing it; these pioneers unleashed the beast of creativity around the world because that original idea has been the inspiration of hundreds of scientific groups for the design of many versatile delivery systems based on mesoporous materials. Because the dream is not the destination, it is the journey, the present review aims to summarise the chain of events that catapulted a small and young research team from the grassroots of academia to the elite of the Biomedical Engineering field.

Mesoporous silica incorporated PCL/Curcumin nanofiber for wound healing application

Electrospinning, a recent fast-emerging technique highly applicable in the production of nanofibers has gained vast recognition owing to its explicit applications in various domains. Amongst which, the production of nanoscaffolds for wound healing applications has been focused recently due to advantages over conventional wound healing methods. In the present research, a composite nanoscaffold comprising SBA-15 (Santa Barbara Amorphous), amine functionalized SBA-15 polycaprolactone (PCL) and curcumin was investigated for its potentiality in wound healing therapeutics. The high biocompatibility and cell adhesion of amine functionalized SBA-15 and the widely explored antimicrobial properties of curcumin added benefit for the wound healing target. The prepared highly interconnected electrospun fibers with porous structure were characterized through various studies such as FTIR, XRD, SEM and EDAX. Further, antibacterial studies against both Gram positive (Bacillus subtilis) and Gram negative (Escherichia coli) strains revealed an improved zone of inhibition. Major invitro studies such as cell migration, proliferation, bio-compatibility was experimented through cell adhesion and live and dead assay using Swiss 3T6 cell lines. In vivo studies on female Wister rats using the fabricated nanofibers incorporated with curcumin and amine functionalized SBA-15 showed 99% scar-less wound healing within 21 days. Re-epithelization of tissue, collagen deposition and formation of granulation tissue were observed from the results of Hematoxylin-Eosin and Masson's tri-chrome staining. From the observations, it can be concluded that the fabricated nanoscaffold could be an effective substrate for wound healing therapeutics.

Nanoantibiotics Based in Mesoporous Silica Nanoparticles: New Formulations for Bacterial Infection Treatment

This review focuses on the design of mesoporous silica nanoparticles for infection treatment. Written within a general context of contributions in the field, this manuscript highlights the major scientific achievements accomplished by professor Vallet-Regí's research group in the field of silica-based mesoporous materials for drug delivery. The aim is to bring out her pivotal role on the envisage of a new era of nanoantibiotics by using a deep knowledge on mesoporous materials as drug delivery systems and by applying cutting-edge technologies to design and engineer advanced nanoweapons to fight infection. This review has been divided in two main sections: the first part overviews the influence of the textural and chemical properties of silica-based mesoporous materials on the loading and release of antibiotic molecules, depending on the host-guest interactions. Furthermore, this section also remarks on the potential of molecular modelling in the design and comprehension of the performance of these release systems. The second part describes the more recent advances in the use of mesoporous silica nanoparticles as versatile nanoplatforms for the development of novel targeted and stimuli-responsive antimicrobial nanoformulations for future application in personalized infection therapies.

Mesoporous silica nanoparticles containing copper or silver synthesized with a new metal source: Determination of their structure parameters and cytotoxic and irritating effects

One of the potential implementation of mesoporous silica nanomaterials (MSNs) is their use in biomedical applications as adsorbents or carriers of various bioactive substances. In this study, we attempted to fabricate silica nanomaterials containing copper and silver that were introduced into the MSN matrix, for the first time using oxalate compounds as a metal source. The syntheses were carried out using hydrothermal and impregnation methods. Structure studies revealed that the obtained nanoparticles were of a spheroidal shape and most had diameters in the range 200-500 nm. Silver and copper were found to be grouped into clusters in most samples, except in copper-decorated MSNs prepared with the impregnation method, which had an even distribution of metal atoms throughout the volume of the granule. An evaluation of the cytotoxic and irritating effects revealed that the preferred candidates for potential future applications in medicine or cosmetology among materials obtained with the presented method are the copper-conjugated MSNs.

Enantioselective effect of cysteine functionalized mesoporous silica nanoparticles in U87 MG and GM08680 human cells and Staphylococcus aureus bacteria

Chirality is a fundamental phenomenon in biological systems, since most of the biomolecules and biological components and species are chiral and therefore recognize and respond differently depending on the enantiomer present. With increasing research into the use of nanomaterials for biomedical purposes, it is essential to understand the role that chirality of nanoparticles plays at the cellular level. Here, the chiral cysteine functionalization of mesoporous silica nanoparticles has been shown to broadly affect its interaction with U87 MG human glioblastoma cell, healthy human fibroblast (GM08680) and methicillin-resistant S. aureus bacteria. We believe that this research is important to further advancement of nano-biotechnology.

Recent Advances Toward the Use of Mesoporous Silica Nanoparticles for the Treatment of Bacterial Infections

It is a fact that the use of antibiotics is inducing a growing resistance on bacteria. This situation is not only the consequence of a drugs’ misuse, but a direct consequence of a widespread and continuous use. Current studies suggest that this effect could be reversed by using abandoned antibiotics to which bacteria have lost their resistance, but this is only a temporary solution that in near future would lead to new resistance problems. Fortunately, current nanotechnology offers a new life for old and new antibiotics, which could have significantly different pharmacokinetics when properly delivered; enabling new routes able to bypass acquired resistances. In this contribution, we will focus on the use of porous silica nanoparticles as functional carriers for the delivery of antibiotics and biocides in combination with additional features like membrane sensitizing and heavy metal-driven metabolic-disrupting therapies as two of the most interesting combination therapies.

Mesoporous Silica-Bioglass Composite Pellets as Bone Drug Delivery System with Mineralization Potential

For decades, local bone drug delivery systems have been investigated in terms of their application in regenerative medicine. Among them, inorganic polymers based on amorphous silica have been widely explored. In this work, we combined two types of amorphous silica: bioglass and doxycycline-loaded mesoporous silica MCM-41 into the form of spherical granules (pellets) as a bifunctional bone drug delivery system. Both types of silica were obtained in a sol-gel method. The drug adsorption onto the MCM-41 was performed via adsorption from concentrated doxycycline hydrochloride solution. Pellets were obtained on a laboratory scale using the wet granulation-extrusion-spheronization method and investigated in terms of physical properties, drug release, antimicrobial activity against Staphylococcus aureus, mineralization properties in simulated body fluid, and cytotoxicity towards human osteoblasts. The obtained pellets were characterized by satisfactory mechanical properties which eliminated the risk of pellets cracking during further investigations. The biphasic drug release from pellets was observed: burst stage (44% of adsorbed drug released within the first day) followed by prolonged release with zero-order kinetics (estimated time of complete drug release was 19 days) with maintained antimicrobial activity. The progressive biomimetic apatite formation on the surface of the pellets was observed. No cytotoxic effect of pellets towards human osteoblasts was noticed.

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.

Antimicrobial and antibiofilm activities of meropenem loaded-mesoporous silica nanoparticles against carbapenem-resistant Pseudomonas aeruginosa

The aims of the present study were the determination of antimicrobial and antibiofilm effects of meropenem-loaded mesoporous silica nanoparticles (MSNs) on carbapenem resistant Pseudomonas aeruginosa (P. aeruginosa) and cytotoxicity properties in vitro. The meropenem-loaded MSNs had shown antibacterial and biofilm inhibitory activities on all isolates at different levels lower than MICs and BICs of meropenem. The viability of HC-04 cells treated with serial concentrations as MICs and BICs of meropenem-loaded MSNs was 92-100%. According to the obtained results, meropenem-loaded MSNs display the significant antibacterial and antibiofilm effects against carbapenem resistant and biofilm forming P. aeruginosa and low cell toxicity in vitro. Then, the prepared system can be an appropriate option for the delivery of carbapenem for further evaluation in vivo assays.

Short-Term Oral Administration of Mesoporous Silica Nanoparticles Potentially Induced Colon Inflammation in Rats Through Alteration of Gut Microbiota

PURPOSE

Mesoporous silica (MSNs) have attracted considerable attention for its application in the field of drug delivery and biomedicine due to its high surface area, large pore volume, and low toxicity. Recently, numerous studies revealed that gut microbiota is of critical relevance to host health. However, the toxicological studies of MSNs were mainly based on the degradation, biodistribution, and excretion in mammalian after oral administration for now. Here in this study, we explored the impacts of oral administration of three kinds of MSNs on gut microbiota in rats to assess its potential toxicity.

METHODS

Forty rats were divided into four groups: control group; Mobil Composition of Matter No. 41 type mesoporous silica (MCM-41) group; Santa Barbara Amorphous-15 type mesoporous silica (SBA-15) group, and biodegradable dendritic center-radial mesoporous silica nanoparticle (DMSN) group. Fecal samples were collected 3 days and 7 days after the intake of MSNs and analyzed with high throughput sequencing. Gastric tissues in rats were obtained after dissection for the histological study.

RESULTS

Three different MSNs (MCM-41, SBA-15, and DMSN) were successfully prepared in this study. The pore size of three MSNs was calculated similarly as (3.54 ± 0.15) nm, (3.48 ± 0.21) nm, and (3.45 ± 0.17) nm according to the BET & BJH model, respectively, while the particle size of MCM-41, SBA-15 and DMSN was around 209.2 nm, 1349.56 nm, and 244.4 nm, respectively. In the gene analysis of 16S rRNA, no significant changes in the diversity and richness were found between groups, while Verrucomicrobia decreased and Candidatus Saccharibacteria increased in MCM-41 treated groups. Meanwhile, no inflammatory and erosion symptoms were observed in the morphological analysis of the colons, except the MCM-41 treated group.

CONCLUSION

Three different MSNs, MCM-41, SBA-15, and DMSN were successfully prepared, and this study firstly suggested the impact of MSNs on the gut microbiota, and further revealing the potential pro-inflammatory effects of oral administration of MCM-41 was possibly through the changing of gut microbiota.

Enhanced photodynamic antimicrobial activity of surface modified SiNPs doped with zinc(II) phthalocyanines: The effect of antimicrobial ampicillin and extra charges from a sultone

1-(2-Methoxyethyl)piperidine sustituted Zn phthalocyanine complex (2) is synthesised and quartenised (3). These complexes are loaded into silica nanoparticles (SiNPs) that are futher surface modified with ampicillin and 1.3-propanesultone. The photophysical and photochemical properties of the complexes and their doped conjugates were investigated in dimethylsulfoxide. The cationic complex (3) is used for photodynamic antimicrobial activity. Log reduction values of above 9 are obtained towards the photoiactivation of Staphyloccocus aureus.

Targeted Stimuli-Responsive Mesoporous Silica Nanoparticles for Bacterial Infection Treatment

The rise of antibiotic resistance and the growing number of biofilm-related infections make bacterial infections a serious threat for global human health. Nanomedicine has entered into this scenario by bringing new alternatives to design and develop effective antimicrobial nanoweapons to fight against bacterial infection. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique characteristics that make them ideal nanocarriers to load, protect and transport antimicrobial cargoes to the target bacteria and/or biofilm, and release them in response to certain stimuli. The combination of infection-targeting and stimuli-responsive drug delivery capabilities aims to increase the specificity and efficacy of antimicrobial treatment and prevent undesirable side effects, becoming a ground-breaking alternative to conventional antibiotic treatments. This review focuses on the scientific advances developed to date in MSNs for infection-targeted stimuli-responsive antimicrobials delivery. The targeting strategies for specific recognition of bacteria are detailed. Moreover, the possibility of incorporating anti-biofilm agents with MSNs aimed at promoting biofilm penetrability is overviewed. Finally, a comprehensive description of the different scientific approaches for the design and development of smart MSNs able to release the antimicrobial payloads at the infection site in response to internal or external stimuli is provided.

Functionalised calcium carbonate as a coformer to stabilize amorphous drugs by mechanochemical activation

The aim of this study was to investigate the amorphization, physical stability and drug release of a model drug, carvedilol (CAR), when loaded onto functionalised calcium carbonate (FCC) using mechanochemical activation (vibrational ball milling). The solid-state characteristics and physical stability of CAR-FCC samples, prepared at different weight ratios and for different milling times, were determined using differential scanning calorimetry and X-ray powder diffraction. Upon milling CAR-FCC samples containing 50% CAR, amorphization of CAR was observed after 10 min. For CAR-FCC samples milled for either 30 or 90 min, it was found that CAR was amorphised at all ratios (10-90% CAR), but FCC remained crystalline. The glass transition temperature (T_gα) of the various CAR-FCC samples milled for 90 min was found to be similar (38 °C) for all ratios containing 20% CAR and above. The similar T_gαs for the different drug ratios indicate deposition of amorphous CAR onto the surface of FCC. For CAR-FCC samples containing 10% CAR, a T_gα of 49 °C was found, which is 11 °C higher compared with other CAR-FCC samples. This may indicate restricted molecular mobility resulting from CAR molecules that are in close contact with the FCC surface. The physical stability, under both stress (100 °C) and non-stress conditions (25 °C at dry conditions), showed that drug concentrations up to 30% CAR can be stabilized in the amorphous form for at least 19 weeks under non-stress conditions when deposited onto FCC, compared to less than a week physical stability of neat amorphous CAR. In vitro drug release showed that CAR-FCC samples containing 60% CAR and below can improve the drug release and generate supersaturated systems compared to neat amorphous and crystalline CAR. Samples with lower drug concentrations (40% CAR and below) can maintain supersaturation during 360 min of dissolution testing. This study indicates that the crystalline inorganic material, FCC, can facilitate amorphization of drugs, provide stabilization against drug crystallization, and improve dissolution properties of amorphous drugs upon mechanochemical activation.

Advances in Laser Ablation Synthesized Silicon-Based Nanomaterials for the Prevention of Bacterial Infection

Nanomaterials have unique properties and characteristics derived from their shape and small size that are not present in bulk materials. If size and shape are decisive, the synthesis method used, which determines the above parameters, is equally important. Among the different nanomaterial’s synthesis methods, we can find chemical methods (microemulsion, sol-gel, hydrothermal treatments, etc.), physical methods (evaporation-condensation, laser treatment, etc.) and biosynthesis. Among all of them, the use of laser ablation that allows obtaining non-toxic nanomaterials (absence of foreign compounds) with a controlled 3D size, has emerged in recent years as a simple and versatile alternative for the synthesis of a wide variety of nanomaterials with numerous applications. This manuscript reviews the latest advances in the use of laser ablation for the synthesis of silicon-based nanomaterials, highlighting its usefulness in the prevention of bacterial infection.

Silica Nanoparticles-A Versatile Tool for the Treatment of Bacterial Infections

The rapid emergence of drug resistance continues to outpace the development of new antibiotics in the treatment of infectious diseases. Conventional therapy is currently limited by drug access issues such as low intracellular drug accumulations, drug efflux by efflux pumps and/or enzymatic degradation. To improve access, targeted delivery using nanocarriers could provide the quantum leap in intracellular drug transport and retention. Silica nanoparticles (SiNPs) with crucial advantages such as large surface area, ease-of-functionalization, and biocompatibility, are one of the most commonly used nanoparticles in drug delivery applications. A porous variant, called the mesoporous silica nanoparticles (MSN), also confers additional amenities such as tunable pore size and volume, leading to high drug loading capacity. In the context of bacterial infections, SiNPs and its variants can act as a powerful tool for the targeted delivery of antimicrobials, potentially reducing the impact of high drug dosage and its side effects. In this review, we will provide an overview of SiNPs synthesis, its structural proficiency which is critical in loading and conjugation of antimicrobials and its role in different antimicrobial applications with emphasis on intracellular drug targeting in anti-tuberculosis therapy, nitric oxide delivery, and metal nanocomposites. The role of SiNPs in antibiofilm coatings will also be covered in the context of nosocomial infections and surgical implants.

Amino-Functionalized Mesoporous Silica Nanoparticle-Encapsulated Octahedral Organoruthenium Complex as an Efficient Platform for Combatting Cancer

In the process of synthesis of a new drug, as important as the drug itself is the formulation used, because the same compound can present a very different efficacy depending on how it is administered. In this work, we demonstrate how the antitumor capacity of a new octahedral organoruthenium complex, [Ru(ppy-CHO)(phen)₂][PF₆] is affected by its encapsulation in different types of mesoporous silica nanoparticles. The interactions between the Ru complex and the silica matrix and how these interactions are affected at two different pHs (7.4 and 5.4, mimicking physiological and endolysosomal acidic conditions, respectively) have been studied. The encapsulation has also been shown to affect the induction of apoptosis and necrosis and progression of the cell cycle compared to the free drug. The encapsulation of the Ru complex in nanoparticles functionalized with amino groups produced very high anticancer activity in cancer cells in vitro, especially against U87 glioblastoma cells, favoring cellular internalization and significantly increasing the anticancer capacity of the initial non-encapsulated Ru complex.

Biomaterials against Bone Infection

Chronic bone infection is considered as one of the most problematic biofilm-related infections. Its recurrent and resistant nature, high morbidity, prolonged hospitalization, and costly medical care expenses have driven the efforts of the scientific community to develop new therapies to improve the standards used today. There is great debate on the management of this kind of infection in order to establish consistent and agreed guidelines in national health systems. The scientific research is oriented toward the design of anti-infective biomaterials both for prevention and cure. The properties of these materials must be adapted to achieve better anti-infective performance and good compatibility, which allow a good integration of the implant with the surrounding tissue. The objective of this review is to study in-depth the antibacterial biomaterials and the strategies underlying them. In this sense, this manuscript focuses on antimicrobial coatings, including the new technological advances on surface modification; scaffolding design including multifunctional scaffolds with both antimicrobial and bone regeneration properties; and nanocarriers based on mesoporous silica nanoparticles with advanced properties (targeting and stimuli-response capabilities).

Multimodal Role of Amino Acids in Microbial Control and Drug Development

Amino acids are ubiquitous vital biomolecules found in all kinds of living organisms including those in the microbial world. They are utilised as nutrients and control many biological functions in microorganisms such as cell division, cell wall formation, cell growth and metabolism, intermicrobial communication (quorum sensing), and microbial-host interactions. Amino acids in the form of enzymes also play a key role in enabling microbes to resist antimicrobial drugs. Antimicrobial resistance (AMR) and microbial biofilms are posing a great threat to the world's human and animal population and are of prime concern to scientists and medical professionals. Although amino acids play an important role in the development of microbial resistance, they also offer a solution to the very same problem i.e., amino acids have been used to develop antimicrobial peptides as they are highly effective and less prone to microbial resistance. Other important applications of amino acids include their role as anti-biofilm agents, drug excipients, drug solubility enhancers, and drug adjuvants. This review aims to explore the emerging paradigm of amino acids as potential therapeutic moieties.

Anti-bacterial activity of inorganic nanomaterials and their antimicrobial peptide conjugates against resistant and non-resistant pathogens

This review details the antimicrobial applications of inorganic nanomaterials of mostly metallic form, and the augmentation of activity by surface conjugation of peptide ligands. The review is subdivided into three main sections, of which the first describes the antimicrobial activity of inorganic nanomaterials against gram-positive, gram-negative and multidrug-resistant bacterial strains. The second section highlights the range of antimicrobial peptides and the drug resistance strategies employed by bacterial species to counter lethality. The final part discusses the role of antimicrobial peptide-decorated inorganic nanomaterials in the fight against bacterial strains that show resistance. General strategies for the preparation of antimicrobial peptides and their conjugation to nanomaterials are discussed, emphasizing the use of elemental and metallic oxide nanomaterials. Importantly, the permeation of antimicrobial peptides through the bacterial membrane is shown to aid the delivery of nanomaterials into bacterial cells. By judicious use of targeting ligands, the nanomaterial becomes able to differentiate between bacterial and mammalian cells and, thus, reduce side effects. Moreover, peptide conjugation to the surface of a nanomaterial will alter surface chemistry in ways that lead to reduction in toxicity and improvements in biocompatibility.

"Outsourcing" Diatoms in Fabrication of Metal-Doped 3D Biosilica

Diatoms have an ability that is unique among the unicellular photoautotrophic organisms to synthesize an intricately ornamented siliceous (biosilica) exoskeleton with an ordered, hierarchical, three-dimensional structure on a micro- to nanoscale. The unique morphological, structural, mechanical, transport, photonic, and optoelectronic properties of diatomaceous biosilica make it a desirable material for modern technologies. This review presents a summary and discussion of published research on the metabolic insertion of chemical elements with specific functional activity into diatomaceous biosilica. Included in the review is research on innovation in methods of synthesis of a new generation of functional siliceous materials, where the synthesis process is "outsourced" to intelligent microorganisms, referred to here as microtechnologists, by providing them with appropriate conditions and reagents.

Nanomaterials with active targeting as advanced antimicrobials

With a growing health threat of bacterial resistance to antibiotics, the nanomaterials have been extensively studied as an alternative. It is assumed that antimicrobial nanomaterials can affect bacteria by several mechanisms simultaneously and thereby overcome antibiotic resistance. Another promising potential use is employing nanomaterials as nanocarriers for antibiotics in order to overcome bacterial defense mechanisms. The passive targeting of nanomaterials is the often used strategy for bacterial treatment, including intracellular infections of macrophages. Furthermore, the specific targeting enhances the efficacy of antimicrobials and reduces side effects. This review aims to discuss advantages, disadvantages, and challenges of nanomaterials in the context of the targeting strategies for antimicrobials as advanced tools for treatments of bacterial infections. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Mesoporous Strontium-Doped Phosphate-Based Sol-Gel Glasses for Biomedical Applications

Mesoporous phosphate-based glasses have great potential as biomedical materials being able to simultaneously induce tissue regeneration and controlled release of therapeutic molecules. In the present study, a series of mesoporous phosphate-based glasses in the P2O5-CaO-Na2O system, doped with 1, 3, and 5 mol% of Sr2+, were prepared using the sol-gel method combined with supramolecular templating. A sample without strontium addition was prepared for comparison. The non-ionic triblock copolymer EO20PO70EO20 (P123) was used as a templating agent. Scanning electron microscopy (SEM) images revealed that all synthesized glasses have an extended porous structure. This was confirmed by N2 adsorption-desorption analysis at 77 K that shows a porosity typical of mesoporous materials. 31P magic angle spinning nuclear magnetic resonance (31P MAS-NMR) and Fourier transform infrared (FTIR) spectroscopies have shown that the glasses are mainly formed by Q1 and Q2 phosphate groups. Degradation of the glasses in deionized water assessed over a 7-day period shows that phosphate, Ca2+, Na+, and Sr2+ ions can be released in a controlled manner over time. In particular, a direct correlation between strontium content and degradation rate was observed. This study shows that Sr-doped mesoporous phosphate-based glasses have great potential in bone tissue regeneration as materials for controlled delivery of therapeutic ions.