Fabrication of zein-coated brush-like silica nanocarriers for high foliage deposition and responsive release of pesticide.

Responsive release systems have received extensive attention to enhance pesticide utilization efficiency and reduce environmental pollution. In this study, pH/GSH dual responsive release system based on brush-like silica (bSiO2) carriers was constructed to enhance the utilization of pesticides. The bSiO2 carriers present core-shell structure, length of 550 nm, diameter of 350 nm and shell thickness of 100 nm. The carrier had a high pesticide loading (20.0 %, w/w) for dinotefuran (Din). After loading Din, zein was covalently linked with cysteine-bridge to seal the loaded pesticides (namely Din@bSiO2@Zein). The Din@bSiO2@Zein exhibited superior foliar affinity, retention and photostability, and retention rate still remain above 95 % with 220 min UV irradiation. Din@bSiO2@Zein displayed pH/GSH responsive release and the cumulative release within 92 h was up to 81 % under pH=9/CGSH=6 mM, mimicking the microenvironment of lepidopteran. The Din@bSiO2@Zein possessed good control efficacy against Plutella xylostella. Appreciably, Din@bSiO2@Zein could be transported bi-directionally to various regions of tobacco plants within 24 h, which had potential to promote pesticide efficacy. This work offers a strategy to minimize the pesticide dosage and encourage sustainable agricultural development.

Multifunctional Mesoporous Silica Nanosheets for Smart Pesticide Delivery and Enhancing Pesticide Deposition.

A multifunctional nanopesticide delivery system is considered to be a novel and efficient tool for controlling pests in modern agriculture. In this study, a mesoporous silica nanosheet (H-MSN) carrier for intelligent delivery of pesticides was prepared by the sol-gel method. The prepared H-MSN carrier had obvious hexagonal flat structure, with a specific surface area of 759.9 m2/g, a transverse diameter of about 340 nm, a thickness of about 80 nm, and regular channels being perpendicular to the plane. Polyethylene glycol diacrylate (PEGDA) and sulfhydryl-modified polyethylenimide (PEI-SH) were used to block the insecticide after loading the insecticide imidacloprid (IMI). The introduction of hydrophilic PEI-SH/PEGDA greatly improved the leaf wettability and adhesion ability of H-MSN. The retention amount of IMI@H-MSN@PEI-SH/PEGDA on cucumber and cabbage leaves was up to 46.0 mg/cm2 and 19.0 mg/cm2, respectively. IMI@H-MSN@PEI-SH/PEGDA showed pH- and GSH-responsive release. Compared with pure IMI, IMI entrapped in MSN carriers has favorable biocompatibility and antiphotolytic properties.

Carboxymethyl ß-cyclodextrin grafted hollow copper sulfide@mesoporous silica carriers for stimuli-responsive pesticide delivery.

Stimuli-responsive controlled release systems have received extensive attention to improve the pesticide bioavailability and minimize environmental pollution. Herein, a multiple stimuli-responsive IMI@HCuS@mSiO2 @ -ss-CßCD delivery system was constructed using modified carboxymethyl ß-cyclodextrin (CßCD-ss-COOH) as sealing materials, hollow copper sulfide nanoparticles with amino-functionalized mesoporous silica shell (HCuS@mSiO2-NH2) as carriers and imidacloprid (IMI) as the model drug. The cavity structure of HCuS@mSiO2-NH2 would provide a large space for pesticide loading. The results revealed that HCuS@mSiO2-ss-CßCD was approximately 230 nm in size and the loading efficiency for IMI was 25.7%, and exhibited better biosafety on bacteria and seed. HCuS carriers were also served as photothermal agent and possessed high photothermal conversion effect (η = 38.4%). IMI@HCuS@mSiO2 @ -ss-CßCD displayed excellent foliage adhesion and multiple stimuli-responsive release properties to pH, α-amylase, GSH, and NIR. The photostability of IMI embedded in CuS@mSiO2 @ -ss-CßCD was approximately 10 times that of IMI solution. This work provides an efficient nanoplatform for realizing pesticide delivery.

Polydopamine-encapsulated cap-like mesoporous silica based delivery system for responsive pesticide release and high retention.

Nanopesticides formulation has been applied in modern agriculture, but the effective deposition of pesticides on plant surfaces is still a critical challenge. Here, we developed a cap-like mesoporous silica (C-mSiO2) carrier for pesticide delivery. The C-mSiO2 carriers with surface amino groups present uniform cap-like shape and have an mean diameter of 300 nm and width of 100 nm. This structure would reduce the rolling and bouncing of carriers on plant leaves, leading to improving the foliage deposition and retention. After loading dinotefuran (DIN), polydopamine (PDA) was used to encapsulate the pesticide (DIN@C-mSiO2@PDA). The C-mSiO2 carriers exhibit high drug loading efficiency (24.7%) and benign biocompatibility on bacteria and seed. Except for pH/NIR response release, the DIN@C-mSiO2@PDA exhibited excellent photostability under UV irradiation. Moreover, the insecticidal activity of DIN@C-mSiO2@PDA was comparable to that of pure DIN and DIN commercial suspension (CS-DIN). This carrier system has the potential for improving the foliage retention and utilization of pesticides.

Enzyme/GSH/pH-responsive hyaluronic acid grafted porous silica nanocarriers bearing Ag2S QDs for fluorescence imaging and combined therapy.

Hyaluronic acid (HA) is a naturally polysaccharide that has been used for drug delivery, but is limited by low drug loading capacity and drug leakage in circulation. To improve drug delivery efficient, HA modified porous silica (pSiO2) nanocarriers were successfully prepared for drug delivery and combining therapy. pSiO2 nanocarriers have stable porous structure and high loading capacity, and pSiO2/HA nanocarriers would possess advantages of HA-based carriers and pSiO2 nanoparticles. Herein, pSiO2 nanocarriers were prepared by two-phase process, followed by embedding Ag2S QDs in the pore walls of pSiO2 carriers, which render the carriers photothermal effect. pSiO2 nanocarriers have size of 30 nm, large channels, and high loading capacity (29.3 %). To graft HA, a sensitive linker with alkyl amine and disulfide bond was conjugated on the surface of Ag2S/pSiO2 nanocarriers by three-step reaction. After loading doxorubicin (DOX), HA was grafted via sensitive linker onto the surface of Ag2S/pSiO2 carriers via the formation of amide bonds to seal the loaded drugs. The interaction between HA and CD44 confers the carrier targeting ability to cancer cells. HA coating can be degraded by hyaluronidase resulting in the release of internal cargo. The Ag2S/pSiO2/HA nanocarriers performs responsive drug release and combining photothermal chemotherapy.

pH and NIR responsive polydopamine-doped dendritic silica carriers for pesticide delivery.

The stimuli-responsive pesticide delivery system provides a powerful strategy for enhancing the effective utilization of pesticides and reducing environmental pollution. Here, we prepared a new polydopamine doped dendritic silica (SiO2/PDA) nanocarriers for pesticide delivery. The SiO2/PDA nanocarriers present uniform spheres with an average diameter of 250 nm and carry center-radial inner pores. After loading dinotefuran (DNF) insecticide, polyethyleneimine (PEI) was used to cap the loaded-pesticide pores. The resulting SiO2/PDA@PEI displays high photothermal conversion effect (η = 35.1 %) and pH and near infrared (NIR) light-responsive release behavior. Meanwhile, the SiO2/PDA and SiO2/PDA@PEI carriers displayed high adhesion and wettability to leaves, and the photostability of DNF encapsulated in SiO2/PDA@PEI was improved by nearly 10 times greater than for free DNF. Importantly, the SiO2/PDA carriers possessed a benign biocompatibility on Escherichia coli (E. coli), seed and cells. Therefore, this work provides a promising approach to improve the utilization of pesticide.

Fabrication of a smart drug delivery system based on hollow Ag2S@mSiO2 nanoparticles for fluorescence-guided synergistic photothermal chemotherapy.

A novel near-infrared (NIR) light-triggered smart nanoplatform has been developed for cancer targeting and imaging-guided combined photothermal-chemo treatment. Notably, Ag2S has a dual function of photothermal therapy and fluorescence imaging, which greatly simplifies the structure of the system. It can emit fluorescence at 820 nm under an excitation wavelength of 560 nm. The phase-change molecule of 1-tetradecanol (TD) is introduced as a temperature-sensitive gatekeeper to provide the nanocarrier with controlled release capability of doxorubicin (DOX). The nanocarrier (HAg2S@mSiO2-TD/DOX) shows a high drug loading capacity of 26.3% and exhibits an apparent NIR-responsive DOX release property. Under NIR irradiation, the photothermal effect of HAg2S nanocores facilitated the release of DOX through the melting of TD. The cytotoxicity test shows that the nanocarriers have good biocompatibility. As the same time, the synergistic combination leads to a better cancer inhibition effect than individual therapy alone in vitro. Cell uptake tests indicate that the carriers have excellent fluorescence imaging ability and high cellular uptake for HepG2 cells. This work provides a new strategy for the fabrication of smart nanocarriers with simple structures for fluorescence-mediated combination cancer therapy. Fabrication of a smart drug delivery system based on hollow Ag2S@mSiO2 nanoparticles for fluorescence-guided synergistic photothermal chemotherapy.

Construction of Double-Shelled Hollow Ag2S@Polydopamine Nanocomposites for Fluorescence-Guided, Dual Stimuli-Responsive Drug Delivery and Photothermal Therapy.

The design and preparation of multifunctional drug carriers for combined photothermal-chemotherapy of cancer have attracted extensive attention over the past few decades. However, the development of simple-structured stimuli-responsive theranostic agents as both photothermal agents and chemotherapeutic agents remains a big challenge. Herein, a novel double-shelled nanocarrier composed of hollow Ag2S (HAg2S) nanospheres and a mesoporous polydopamine (MPDA) exterior shell was fabricated through a facile process. Notably, HAg2S possesses both fluorescence and photothermal properties. MPDA acts as a drug carrier and photothermal agent. Meanwhile, the cavity structure between HAg2S and MPDA provides more space for drug loading. The nanocarrier presents a high drug loading rate of 23.4%. It exhibits an apparent pH-responsive DOX release property due to the acidic sensitivity of PDA. In addition, the release of DOX is promoted under NIR irradiation, which is attributed to the heating action generated by the photothermal effect of HAg2S and MPDA. The cytotoxicity test shows that the nanocarriers possess good biocompatibility. Compared with single photothermal therapy or chemotherapy, the combined treatment represents a synergistic effect with higher therapeutic efficacy. In addition, the nanocarriers exhibit excellent fluorescence imaging capability and can target HepG2 cells. These simple-structured smart nanocarriers have a great potential for fluorescence-mediated combination cancer therapy.

Mussel-Inspired Fabrication of PDA@PAN Electrospun Nanofibrous Membrane for Oil-in-Water Emulsion Separation.

Emulsified oily wastewater threatens human health seriously, and traditional technologies are unable to separate emulsion containing small sized oil droplets. Currently, oil-water emulsions are usually separated by special wettability membranes, and researchers are devoted to developing membranes with excellent antifouling performance and high permeability. Herein, a novel, simple and low-cost method has been proposed for the separation of emulsion containing surfactants. Polyacrylonitrile (PAN) nanofibers were prepared via electrospinning and then coated by polydopamine (PDA) by using self-polymerization reactions in aqueous solutions. The morphology, structure and oil-in-water emulsion separation properties of the as-prepared PDA@PAN nanofibrous membrane were tested. The results show that PDA@PAN nanofibrous membrane has superhydrophilicity and almost no adhesion to crude oil in water, which exhibits excellent oil-water separation ability. The permeability and separation efficiency of n-hexane/water emulsion are up to 1570 Lm-2 h-1 bar-1 and 96.1%, respectively. Furthermore, after 10 cycles of separation, the permeability and separation efficiency values do not decrease significantly, indicating its good recycling performance. This research develops a new method for preparing oil-water separation membrane, which can be used for efficient oil-in-water emulsion separation.

Facile One-Step Deposition of Ag Nanoparticles on SiO2 Electrospun Nanofiber Surfaces for Label-Free SERS Detection and Antibacterial Dressing.

The fabrication of highly active and free-standing surface-enhanced Raman scattering (SERS) substrates in a simple and low-cost manner has been a crucial and urgent challenge in recent years. Herein, SiO2 nanofiber substrates modified with size-tunable Ag nanoparticles were prepared by the combination of electrospinning and in situ chemical reduction. The results demonstrate the presence and uniform adsorption of Ag nanoparticles on the SiO2 matrix surface. The free-standing composite nanofibrous substrates show high-performance SERS response toward 4-mercaptophenol and 4-mercaptobenzoic acid, and the detection limit can be as low as 10-10 mol/L. Most importantly, the as-prepared substrate as a versatile SERS platform can realize label-free detection of bio-macromolecules of bacteria, i.e., Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Furthermore, the substrates also possess outstanding antibacterial activities against S. aureus and E. coli. Briefly, the significance of this study is that size-tunable Ag nanoparticles can be decorated on SiO2 nanofiber surfaces with triethanolamine as a bridging and reducing agent through a one-pot reaction, and the as-prepared nanofibrous membranes are expected to act as a candidate for label-free SERS detection as well as antibacterial dressing.

Loading of Au/Ag Bimetallic Nanoparticles within and Outside of the Flexible SiO2 Electrospun Nanofibers as Highly Sensitive, Stable, Repeatable Substrates for Versatile and Trace SERS Detection.

In this paper, we propose a facile and cost-effective electrospinning technique to fabricate surface-enhanced Raman scattering (SERS) substrates, which is appropriate for multiple analytes detection. First of all, HAuCl4∙3H2O was added into the TEOS/PVP precursor solution, and flexible SiO2 nanofibers incorporated with gold nanoparticles (SiO2@Au) were prepared by electrospinning and calcination. Subsequently, the nanofibrous membranes were immersed in the tannic acid and 3-aminopropyltriethoxysilane solution for surface modification through Michael addition reaction. Finally, the composite nanofibers (Ag@T-A@SiO2@Au) were obtained by the in-situ growth of Ag nanoparticles on the surfaces of nanofibers with tannic acid as a reducing agent. Due to the synergistic enhancement of Au and Ag nanoparticles, the flexible and self-supporting composite nanofibrous membranes have excellent SERS properties. Serving as SERS substrates, they are extremely sensitive to the detection of 4-mercaptophenol and 4-mercaptobenzoic acid, with an enhancement factor of 108. Moreover, they could be utilized to detect analytes such as pesticide thiram at a low concentration of 10-8 mol/L, and the substrates retain excellent Raman signals stability during the durability test of 60 days. Furthermore, the as-fabricated substrates, as a versatile SERS platform, could be used to detect bacteria of Staphylococcus aureus without a specific and complicated bacteria-aptamer conjugation procedure, and the detection limit is up to 103 colony forming units/mL. Meanwhile, the substrates also show an excellent repeatability of SERS response for S. aureus organelles. Briefly, the prime novelty of this work is the fabrication of Au/Ag bimetallic synergetic enhancement substrates as SERS platform for versatile detection with high sensitivity and stability.

A Facile Method for the Fabrication of Silver Nanoparticles Surface Decorated Polyvinyl Alcohol Electrospun Nanofibers and Controllable Antibacterial Activities.

Polyvinyl alcohol (PVA) electrospun nanofibers (NFs) are ideal carriers for loading silver nanoparticles (Ag NPs) serving as antibacterial materials. However, it is still a challenge to adjust the particles size, distribution, and loading density via a convenient and facile method in order to obtain tunable structure and antimicrobial activities. In this study, Ag NPs surface decorated PVA composite nanofibers (Ag/PVA CNFs) were fabricated by the solvothermal method in ethylene glycol, which plays the roles of both reductant and solvent. The morphology and structure of the as-fabricated Ag/PVA CNFs were characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, UV-visible spectroscopy, and Fourier transform infrared spectroscopy. Ag NPs had an average diameter of 30 nm, the narrowest size distribution and the highest loading density were successfully decorated on the surfaces of PVA NFs, at the AgNO3 concentration of 0.066 mol/L. The antibacterial properties were evaluated by the methods of absorption, turbidity, and growth curves. The as-fabricated Ag/PVA hybrid CNFs exhibit excellent antimicrobial activities with antibacterial rates over 98%, especially for the sample prepared with AgNO3 concentration of 0.066 mol/L. Meanwhile, the antibacterial effects are more significant in the Gram-positive bacteria of Staphylococcus aureus (S. aureus) than the Gram-negative bacteria of Escherichia coli (E. coli), since PVA is more susceptive to S. aureus. In summary, the most important contribution of this paper is the discovery that the particles size, distribution, and loading density of Ag NPs on PVA NFs can be easily controlled by adjusting AgNO3 concentrations, which has a significant impact on the antibacterial activities of Ag/PVA CNFs.

Highly Sensitive Surface-Enhanced Raman Spectroscopy Substrates of Ag@PAN Electrospinning Nanofibrous Membranes for Direct Detection of Bacteria.

Surface-enhanced Raman spectroscopy (SERS) can be applied for biological detection because of its high sensitivity and noninvasiveness for analytes. Herein, we engineer plasmonic free-standing substrates composed of Ag nanoparticles (NPs) supported on polyacrylonitrile (PAN) electrospinning nanofibrous felts as sensors for bacterial detection. Ag NPs are evenly distributed on PAN nanofibers after preimpregnation and impregnation of PAN nanofibers in Tollens' reagent. The size and loading density of Ag NPs are tunable by adjusting the reaction time of glucose and Tollens' reagent, thereby allowing the tuning of the surface plasmon resonance. Using 4-mercaptophenol (4-MPh) and 4-mercaptobenzoic acid (4-MBA) as probe molecules, SERS effects of Ag@PAN composite nanofibers are investigated, and the substrates allow the detection of 4-MPh and 4-MBA at a low concentration of 10-9 mol/L. Importantly, the substrates exhibit a high sensitivity of SERS performance for bacterial identification without a specific bacteria-aptamer conjugation. The SERS substrates also show good uniformity of SERS response for bacterial organelles. Furthermore, the antimicrobial property was evaluated, and the results indicate that the sample of Ag@PAN nanofiber mats possesses excellent antibacterial properties against Escherichia coli and Staphylococcus aureus.

Fabrication of biodegradable auto-fluorescent organosilica nanoparticles with dendritic mesoporous structures for pH/redox-responsive drug release.

In this work, disulfide-bridged organic silica (OS) based nanocarriers were constructed for drug release. The broken of SS bonds in Si-O-Si skeleton would improve the degradation of Si-O-Si of OS carriers. The OS carriers have a central-radiated dendritic porous structure and a large specific surface area of 453.80 m2g-1. The dextrin was selectively oxidized to dialdehyde dextrin (DAD) and then was modified on the surface of OS carriers by Schiff base bonds. Subsequently, cystamine (Cys) was linked with DAD to form DAD/Cys layer (OS-N=C-DAD/Cys) to seal the loaded drug. The DAD/Cys layer display the degradation performance of pH/GSH dual response The obtained OS-N=C-DAD/Cys carriers displayed low premature and the cumulative release was 6.5% under normal physiological conditions within 48 h. The Schiff base (-N=C-) structure in the DAD/Cys layer is also capable of monitoring acid-responsive drug release by fluorescence change. The prepared OS-N=C-DAD/Cys carriers and their degraded products have high biocompatibility.

A porous nano-adsorbent with dual functional groups for selective binding proteins with a low detection limit.

In this study, porous silica nanoparticles functionalized with a thiol group (SiO2-SH NPs) were synthesized via a one-pot method. Subsequently, iminodiacetic acid was modified, and further adsorption of Ni2+ ions was conducted to obtain a SiO2-S/NH-Ni nano-adsorbent. Then, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TG) and X-ray diffraction (XRD) were employed to characterize its morphology and composition. The results indicate that the SiO2-S/NH-Ni nano-adsorbent is porous, has an average diameter of 77.1 nm and has a small porous structure of about 3.7 nm in the silica skeleton. The Brunauer-Emmett-Teller (BET) surface area and total pore volume were 537.2 m2 g-1 and 3.3 cm3 g-1, respectively, indicating a large BET surface area. The results indicate that the as-prepared SiO2-S/NH-Ni nano-adsorbent would be suitable to selectively and efficiently bind His-tagged proteins from an E. coli cell lysate. The SDS-PAGE results show that the as-prepared nano-adsorbent presents specifically to both His-tagged CPK4 and His-tagged TRX proteins, indicating the nano-adsorbent can be used to effectively separate His-tagged proteins and is universal to all His-tagged fusion proteins. We also found that the as-prepared nano-adsorbent exhibits a low detection limit (1.0 × 10-7 mol L-1) and a strong regeneration ability based on four regeneration experiments that were particularly suited to the separation of His-tagged proteins.

Fabrication of biodegradable Mn-doped mesoporous silica nanoparticles for pH/redox dual response drug delivery.

Mn-doped mesoporous silica (MMS) nanocarriers were prepared by in situ doping Mn component for drug delivery. In the acidic or reductive microenvironment of tumor, the MnO bond can be broken up, and Mn components would be released from the silica framework, thus accelerating the degradation of the silica nanocarrier. Due to the mesoporous structure, MMS nanocarriers have a high specific surface area of 1125.56 m2/g, which is suitable for loading and controlled release of drug. And the encapsulation ratio of Dox and drug loading of MMS and MMS/PDA is 98.08%, 39.54% and 38.81% respectively. After loading Dox, polydopamine(PDA)was coated on the surface of MMS nanocarriers to reduce drug burst release and endow them pH-responsive release. The prepared Dox-MMS/PDA delivery system displays pH/redox dual-responsive degradation of carriers and drug release.

Preparation of hydroxyapatite nanostructures with different morphologies and adsorption behavior on seven heavy metals ions.

Hydroxyapatite (HAP) nanostructures with different morphologies have been successfully synthesized in a facile method and the pH value of the solution has an important effect on morphology. Among them, the porous HAP nanospheres (NSs) with an average diameter of 76 nm were further employed as adsorbent to remove the heavy metal ions in solution. The BET surface area, pore size and pore volume of porous HAP NSs were 45.3 m2·g-1, 2.7 nm and 0.23 m3·g-1, respectively. The ICP results showed that the porous HAP NSs could remove effectively Pb2+, Cd2+, Cu2+, Co2+, Ni2+, Zn2+, Hg2+ ions and the maximum adsorption capacity reached 254.90 mg·g-1. Experimental equilibrium data were also analyzed by the Langmuir and Freundlich models and the best fit was obtained with the Langmuir isotherm equation. The kinetic study indicated that the adsorption of Pb2+ ions on porous HAP NSs was almost instantaneous and the maximum adsorption was reached within 20 min. Compared with the pseudo 1st order model, the adsorption kinetic data was well described by the pseudo 2rd kinetic model. In addition, the porous HAP NSs had a good stability and would be a promising nanoadsorbent for heavy metal ions.

Functionalized Nano-adsorbent for Affinity Separation of Proteins.

Thiol-functionalized silica nanospheres (SiO2-SH NSs) with an average diameter of 460 nm were synthesized through a hydrothermal route. Subsequently, the prepared SiO2-SH NSs were modified by SnO2 quantum dots to afford SnO2/SiO2 composite NSs possessing obvious fluorescence, which could be used to trace the target protein. The SnO2/SiO2 NSs were further modified by reduced glutathione (GSH) to obtain SnO2/SiO2-GSH NSs, which can specifically separate glutathione S-transferase-tagged (GST-tagged) protein. Moreover, the peroxidase activity of glutathione peroxidase 3 (GPX3) separated from SnO2/SiO2-GSH NSs in vitro was evaluated. Results show that the prepared SnO2/SiO2-GSH NSs exhibit negligible nonspecific adsorption, high concentration of protein binding (7.4 mg/g), and good reused properties. In the meantime, the GST-tagged GPX3 separated by these NSs can retain its redox state and peroxidase activity. Therefore, the prepared SnO2/SiO2-GSH NSs might find promising application in the rapid separation and purification of GST-tagged proteins.

Synthesis of silver nanoparticle-decorated hydroxyapatite (HA@Ag) poriferous nanocomposites and the study of their antibacterial activities.

Herein, we demonstrate a facile and green rapid approach for the synthesis of uniform poriferous hydroxylapatite [Ca10(PO4)6(OH)2, HA] and poriferous silver nanoparticle (Ag NPs)-decorated hydroxylapatite (HA@Ag) nanocomposites with excellent antibacterial properties. All the nanocomposites were fully characterized in the solid state via various techniques such as X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), automatic specific surface area and porosity analysis (BET) and field emission scanning electron microscopy (FESEM). The results show that HA has a porous rod-like structure, which the HA@Ag nanocomposites retained, and the surface of HA was loaded with globular-like Ag NPs with an average diameter of about 5.8 nm, which exhibit a well-crystalline state. The experimental parameters such as pH, the molar ratio of HA and Tollens' reagent, and reductant have a significant effect on the size and distribution of the Ag NPs. Moreover, the antimicrobial activities of HA and HA@Ag against Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) were evaluated via broth dilution, filter paper diffusion, optical density (OD600) and electron microscopy observation. The as-prepared HA@Ag nanocomposites exhibit excellent antibacterial activities, especially for S. aureus. The minimum inhibition concentration (MIC) of HA@Ag is only 3.9 µg mL-1.

Construction of multifunctional porous silica nanocarriers for pH/enzyme-responsive drug release.

pH/enzyme-responsive nanocarriers based on porous silica (pSiO2) nanospheres (NSs) were developed for controlled release of drug. The pSiO2 NSs present uniform spheres and have an average diameter of 100nm. The pSiO2 NSs with high specific surface area (835m2·g-1) and the pore volume (1.24cm3·g-1) are suitable for drug loading and the loading capacity reaches to 29% for amoxicillin (AMX) model drug. In this system, protocatechuic acid (PCA) and L-glutamic acid (Glu) as linkers were grafting onto the surface of pSiO2 NSs to conjugate the capping lids. Acid-decomposable ZnO quantum dots (QDs) were introduced to block the partial pores of pSiO2 via amido bonds, which could act as gates and fluorescence probes. To minimize the premature release, hyaluronic acid (HA) was further coating on the outer surface of pSiO2, which would be degraded by over-expressed hyaluronidase (Hyal-1) in the tumor microenvironment. The controlled release of the drug from the ZnO/HA-gated delivery system was realized by the acidic dissolution of ZnO QDs and enzymatic hydrolysis of HA. The obtained ZnO/HA-gated pSiO2 delivery system would achieve minimized premature release and responsive release under a physiological environment.