Biocompatible/bioabsorbable silver nanocomposite coatings

Near-Infrared Induced miR-34a Delivery from Nanoparticles in Esophageal Cancer Treatment

Current nucleic acid delivery methods have not achieved efficient, non-toxic delivery of miRNAs with tumor-specific selectivity. In this study, a new delivery system based on light-inducible gold-silver-gold, core-shell-shell (CSS) nanoparticles is presented. This system delivers small nucleic acid therapeutics with precise spatiotemporal control, demonstrating the potential for achieving tumor-specific selectivity and efficient delivery of miRNA mimics. The light-inducible particles leverage the photothermal heating of metal nanoparticles due to the local surface plasmonic resonance for controlled chemical cleavage and release of the miRNA mimic payload. The CSS morphology and composition result in a plasmonic resonance within the near-infrared (NIR) region of the light spectrum. Through this method, exogenous miR-34a-5p mimics are effectively delivered to human squamous cell carcinoma TE10 cells, leading to apoptosis induction without adverse effects on untransformed keratinocytes in vitro. The CSS nanoparticle delivery system is tested in vivo in Foxn1nu athymic nude mice with bilateral human esophageal TE10 cancer cells xenografts. These experiments reveal that this CSS nanoparticle conjugates, when systemically administered, followed by 850 nm light emitting diode irradiation at the tumor site, 6 h post-injection, produce a significant and sustained reduction in tumor volume, exceeding 87% in less than 72 h.

Photocontrolled miR-148b nanoparticles cause apoptosis, inflammation and regression of Ras induced epidermal squamous cell carcinomas in mice

Despite evidence that microRNAs (miRNAs) are essential in modulating tumorigenesis, a major challenge in cancer treatment is to achieve tumor-specific selectivity and efficient yet safe delivery of miRNAs in vivo. In this study, we have developed a light-inducible silver nanoparticle nucleic acid delivery system that demonstrates precise spatiotemporal control, high cellular uptake, low cytotoxicity, escape from endosomes and release of functional miRNA into the cytosol. Using this approach, we delivered exogenous miR-148b to induce apoptosis in Ras-expressing keratinocytes and murine squamous cell carcinoma cells while avoiding cytotoxicity in untransformed keratinocytes. When administered to transgenic mice with HRas^G12V-driven skin tumors, a single dose of silver nanoparticle conjugates followed by 415 nm LED irradiation at the tumor site caused a rapid and sustained reduction in tumor volume by 92.8%, recruited T cells to the tumor site, and acted as a potent immunomodulator by polarizing the cytokine balance toward Th1 both locally and systemically. In summary, our results demonstrate that spatiotemporal controlled miR-148b mimic delivery can promote tumor regression efficiently and safely.

Water-based 2D printing of magnetically active cellulose derivative nanocomposites

The fabrication of magnetic materials typically involves expensive, non-scalable, time-consuming or toxic processes. Here we report a scalable, quick and environmentally-benign fabrication of magnetically active materials through screen printing using mechanically flexible paper having micron-sized pores as substrates. In comparison with traditional multicomponent inks, simple aqueous dispersions comprising solely water-soluble cellulose derivatives and cobalt ferrite nanoparticles are used. Depending on the cellulosic matrix used, inks with viscosities in the 500-2.500 mPa s range were obtained for shear rates of 20-100 s^-1. Patterns with line widths from 183 to 642 μm with a maximum deviation of 9 % were fabricated. The largest magnetization saturation obtained of 0.024 emu (or 0.021 emu cm^-2) for the hydroxypropyl cellulose-based ink demonstrates enough magnetization for applications in areas such as actuators and sensors. This work provides novel insights towards the processing of renewable, magnetically active and mechanically flexible materials with tailored geometries which use water as the sole solvent.

Collagen-infilled 3D printed scaffolds loaded with miR-148b-transfected bone marrow stem cells improve calvarial bone regeneration in rats

Differentiation of progenitors in a controlled environment improves the repair of critical-sized calvarial bone defects; however, integrating micro RNA (miRNA) therapy with 3D printed scaffolds still remains a challenge for craniofacial reconstruction. In this study, we aimed to engineer three-dimensional (3D) printed hybrid scaffolds as a new ex situ miR-148b expressing delivery system for osteogenic induction of rat bone marrow stem cells (rBMSCs) in vitro, and also in vivo in critical-sized rat calvarial defects. miR-148b-transfected rBMSCs underwent early differentiation in collagen-infilled 3D printed hybrid scaffolds, expressing significant levels of osteogenic markers compared to non-transfected rBMSCs, as confirmed by gene expression and immunohistochemical staining. Furthermore, after eight weeks of implantation, micro-computed tomography, histology and immunohistochemical staining results indicated that scaffolds loaded with miR-148b-transfected rBMSCs improved bone regeneration considerably compared to the scaffolds loaded with non-transfected rBMSCs and facilitated near-complete repair of critical-sized calvarial defects. In conclusion, our results demonstrate that collagen-infilled 3D printed scaffolds serve as an effective system for miRNA transfected progenitor cells, which has a promising potential for stimulating osteogenesis and calvarial bone repair.

Combinatorial Delivery of miRNA-Nanoparticle Conjugates in Human Adipose Stem Cells for Amplified Osteogenesis

It is becoming more apparent in tissue engineering applications that fine temporal control of multiple therapeutics is desirable to modulate progenitor cell fate and function. Herein, the independent temporal control of the co-delivery of miR-148b and miR-21 mimic plasmonic nanoparticle conjugates to induce osteogenic differentiation of human adipose stem cells (hASCs), in a de novo fashion, is described. By applying a thermally labile retro-Diels-Alder caging and linkage chemistry, these miRNAs can be triggered to de-cage serially with discrete control of activation times. The method relies on illumination of the nanoparticles at their resonant wavelengths to generate sufficient local heating and trigger the untethering of the Diels-Alder cycloadduct. Characterization of the photothermal release using fluorophore-tagged miRNA mimics in vitro is carried out with fluorescence measurements, second harmonic generation, and confocal imaging. Osteogenesis of hASCs from the sequential co-delivery of miR-21 and miR-148b mimics is assessed using xylenol orange and alizarin red staining of deposited minerals, and quantitative polymerase chain reaction for gene expression of osteogenic markers. The results demonstrate that sequential miRNA mimic activation results in upregulation of osteogenic markers and mineralization relative to miR-148b alone, and co-activation of miR-148b and miR-21 at the same time.

Comparison of thermally actuated retro-diels-alder release groups for nanoparticle based nucleic acid delivery

The present study explores alternate pericyclic chemistries for tethering amine-terminal biomolecules onto silver nanoparticles. Employing the versatile tool of the retro-Diels-Alder (rDA) reaction, three thermally-labile cycloadducts are constructed that cleave at variable temperature ranges. While the reaction between furan and maleimide has widely been reported, the current study also evaluates the reverse reaction kinetics between thiophene-maleimide, and pyrrole-maleimide cycloadducts. Density Functional Theorem (DFT) calculations used to model and plan the experiments, predict energy barriers for the thiophene-maleimide reverse reaction to be greatest, and the pyrrole-maleimide barriers the lowest. Based on the computational analyses, it is projected that the cycloreversion rate would occur slowest with the thiophene, followed by furan, and finally pyrrole would yield the promptest release. These thermally-responsive linkers, characterized by Electrospray Ionization Mass Spectrometry, ¹H and ¹³C NMR, are thiol-linked to silver nanoparticles and conjugate single stranded siRNA mimics with 5' fluorescein tag. Second harmonic generation spectroscopy (SHG) and fluorescence spectroscopy are used to measure release and rate of release. The SHG decay constants and fluorescence release profiles obtained for the three rDA reactions confirm the trends obtained from the DFT computations.

Plasmon-Enhanced Photocleaving Dynamics in Colloidal MicroRNA-Functionalized Silver Nanoparticles Monitored with Second Harmonic Generation

The photocleaving dynamics of colloidal microRNA-functionalized nanoparticles are studied using time-dependent second harmonic generation (SHG) measurements. Model drug-delivery systems composed of oligonucleotides attached to either silver nanoparticles or polystyrene nanoparticles using a nitrobenzyl photocleavable linker are prepared and characterized. The photoactivated controlled release is observed to be most efficient on resonance at 365 nm irradiation, with pseudo-first-order rate constants that are linearly proportional to irradiation powers. Additionally, silver nanoparticles show a 6-fold plasmon enhancement in photocleaving efficiency over corresponding polystyrene nanoparticle rates, while our previous measurements on gold nanoparticles show a 2-fold plasmon enhancement compared to polystyrene nanoparticles. Characterizations including extinction spectroscopy, electrophoretic mobility, and fluorimetry measurements confirm the analysis from the SHG results. The real-time SHG measurements are shown to be a highly sensitive method for investigating plasmon-enhanced photocleaving dynamics in model drug delivery systems.

Antifungal properties of silver nanoparticles against indoor mould growth

The presence of moulds in indoor environments causes serious diseases and acute or chronic toxicological syndromes. In order to inhibit or prevent the growth of microorganisms on building materials, the disruption of their vital processes or the reduction of reproduction is required. The development of novel techniques that impair the growth of microorganisms on building materials is usually based on silver nanoparticles (AgNPs). It makes them an alternative to other biocides. AgNPs have proven antibacterial activity and became promising in relation to fungi. The aim of the study was to assess growth and morphology of mycelia of typical indoor fungal species: Penicillium brevicompactum, Aspergillus fumigatus, Cladosporium cladosporoides, Chaetomium globosum and Stachybotrys chartarum as well as Mortierella alpina, cultured on agar media. The antifungal activity of AgNPs was also tested in relation to C. globosum and S. chartarum grown on the surface of gypsum drywall. It was found that the presence of AgNPs in concentrations of 30-200mg/l significantly decreased the growth of fungi. However, in the case of M. alpina, AgNPs stimulated its growth. Moreover, strong changes in moulds morphology and colour were observed after administration of AgNPs. Parameters of conidiophores/sporangiophores varied depending on mould region and changed significantly after treatment with AgNPs. The experiments have shown antifungal properties of AgNPs against common indoor mould species. Their application to building materials could effectively protect indoor environments from mould development. However, consideration must be given to the fact that the growth of some fungal strains might be stimulated by AgNPs.

Does surface coating of metallic nanoparticles modulate their interference with in vitro assays?

Experimental setup for in vitro evaluation of metallic nanoparticles where interferences depend on metal core, surface coating, and the test system.

Can a novel silver nano coating reduce infections and maintain cell viability in vitro?

Herein we report a facile layer-by-layer method for creating an antimicrobial coating composed of silver nanoparticles on medical grade titanium test discs. Nanoscale silver nanoparticle layers are attached to the titanium orthopedic implant material via aminopropyltriethoxy silane crosslinker that reacts with neighboring silane moieties to create an interconnected network. A monolayer of silane, followed by a monolayer of silver nanoparticles would form one self-assembled layer and this process can be repeated serially, resulting in increased silver nanoparticles deposition. The release rate of silver ion increases predictably with increasing numbers of layers and at appropriate thicknesses these coatings demonstrate 3-4 log reduction of viable Escherichia coli and Staphylococcus aureus bacteria. Increasing the thickness of the coatings resulted in reduced bacterial colonization as determined by fluorescent staining and image analysis. Interestingly, the cytotoxicity of murine 3T3 cells as quantified by fluorescent staining and flow cytometry, was minimal and did not vary significantly with the coating thickness. Additionally, these coatings are mechanically stable and resist delamination by orthogonal stress test. This simple layer-by-layer coating technique may provide a cost-effective and biocompatible method for reducing microbial colonization of implantable orthopedic devices.

Silver nanoscale antisense drug delivery system for photoactivated gene silencing

The unique photophysical properties of noble metal nanoparticles contribute to their potential as photoactivated drug delivery vectors. Here we demonstrate the synthesis and characterization of 60-80 nm silver nanoparticles (SNPs) decorated with thiol-terminated photolabile DNA oligonucleotides. In vitro assays and fluorescent confocal microscopy of treated cell cultures show efficient UV-wavelength photoactivation of surface-tethered caged ISIS2302 antisense oligonucleotides possessing internal photocleavable linkers. As a demonstration of the advantages of these novel nanocarriers, we investigate properties including: enhanced stability to nucleases, increased hybridization activity upon photorelease, and efficient cellular uptake as compared to commercial transfection vectors. Their potential as multicomponent delivery agents for oligonucleotide therapeutics is shown through regulation of ICAM-1 (Intracellular Adhesion Molecule-1) silencing. Our results suggest a means to achieve light-triggered, spatiotemporally controlled gene silencing via nontoxic silver nanocarriers, which hold promise as tailorable platforms for nanomedicine, gene expression studies, and genetic therapies.

Antimicrobial biocompatible bioscaffolds for orthopaedic implants

Nationally, nearly 1.5 million patients in the USA suffer from ailments requiring bone grafts and hip and other joint replacements. Infections following internal fixation in orthopaedic trauma can cause osteomyelitis in 22-66% of cases and, if uncontrolled, the mortality rate can be as high as 2%. We characterize a procedure for the synthesis of antimicrobial and biocompatible poly-l-lactic acid (PLLA) and poly-ethyleneglycol (PEG) bioscaffolds designed to degrade and absorb at a controlled rate. The bioscaffold architecture aims to provide a suitable substrate for the controlled release of silver nanoparticles (SNPs) to reduce bacterial growth and to aid the proliferation of human adipose-derived stem cells (hASCs) for tissue-engineering applications. The fabricated bioscaffolds were characterized by scanning transmission microscope (SEM) and it showed that the addition of tncreasing concentrations of SNPs results in the formation of dendritic porous channels perpendicular to the axis of precipitation. The antimicrobial properties of these porous bioscaffolds were tested according to a modified ISO 22196 standard across varying concentrations of biomass-mediated SNPs to determine an efficacious antimicrobial concentration. The bioscaffolds reduced the Staphylococcus aureus and Escherichia coli viable colony-forming units by 98.85% and 99.9%, respectively, at an antimicrobial SNPs concentration of 2000 ppm. Human ASCs were seeded on bioscaffolds and cultured in vitro for 20 days to study the effect of SNPs concentration on the viability of cells. SEM analysis and the metabolic activity-based fluorescent dye, AlamarBlue®, demonstrated the growth of cells on the efficacious antimicrobial bioscaffolds. The biocompatibility of in vitro leached silver, quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES), proved non-cytotoxic when tested against hASCs, as evaluated by MTT assay.