103 research outputs found
The influence of intercalating perfluorohexane into lipid shells on nano and microbubble stability
Microbubbles are potential diagnostic and therapeutic agents. In vivo stability is important as the bubbles are required to survive multiple passages through the heart and lungs to allow targeting and delivery. Here we have systematically varied key parameters affecting microbubble lifetime to significantly increase in vivo stability. Whilst shell and core composition are found to have an important role in improving microbubble stability, we show that inclusion of small quantities of C6F14 in the microbubble bolus significantly improves microbubble lifetime. Our results indicate that C6F14 inserts into the lipid shell, decreasing surface tension to 19 mN m-1, and increasing shell resistance, in addition to saturating the surrounding medium. Surface area isotherms suggest that C6F14 incorporates into the acyl chain region of the lipid at a high molar ratio, indicating âŒ2 perfluorocarbon molecules per 5 lipid molecules. The resulting microbubble boluses exhibit a higher in vivo image intensity compared to commercial compositions, as well as longer lifetimes
Reduction in the resident intestinal myelomonocytic cell population occurs during ApcMin/+ mouse intestinal tumorigenesis
With its significant contribution to cancer mortality globally, advanced colorectal cancer (CRC) requires new treatment strategies. However, despite recent good results for mismatch repair (MMR)âdeficient CRC and other malignancies, such as melanoma, the vast majority of MMRâproficient CRCs are resistant to checkpoint inhibitor (CKI) therapy. MMRâproficient CRCs commonly develop from precursor adenomas with enhanced Wntâsignalling due to adenomatous polyposis coli (APC) mutations. In melanomas with enhanced Wnt signalling due to stabilized ÎČâcatenin, immune anergy and resistance to CKI therapy has been observed, which is dependent on microâenvironmental myelomonocytic (MM) cell depletion in melanoma models. However, MM populations of colorectal adenomas or CRC have not been studied. To characterize resident intestinal MM cell populations during the early stages of tumorigenesis, the present study utilized the ApcMin/+ mouse as a model of MMRâproficient CRC, using enhanced green fluorescent protein (EGFP) expression in the mouse lysozyme (Mâlys)lysâEGFP/+ mouse as a panâmyelomonocytic cell marker and a panel of murine macrophage surface markers. Total intestinal lamina propria mononuclear cell (LPMNC) numbers significantly decreased with age (2.32±1.39x107 [n=4] at 33 days of age vs. 1.06±0.24x107 [n=8] at 109 days of age) during intestinal adenoma development in ApcMin/+ mice (P=0.05; unpaired Student's tâtest), but not in wildâtype littermates (P=0.35). Decreased total LPMNC numbers were associated with atrophy of intestinal lymphoid follicles and the absence of MM/lymphoid cell aggregates in ApcMin/+ mouse intestine, but not spleen, compared with wildâtype mice. Furthermore, during the early stage of intestinal adenoma development, there was a twoâfold reduction of Mâlys expressing cells (P=0.05) and fourâfold reduction of ERâHR3 (macrophage subâset) expressing cells (P=0.05; two tailed MannâWhitney U test) in mice with reduced total intestinal LPMNCs (n=3). Further studies are necessary to determine the relevance of these findings to immuneâsurveillance of colorectal adenomas or MMRâproficient CRC CKI therapy resistance
One-step fabrication of hollow-channel gold nanoflowers with excellent catalytic performance and large single-particle SERS activity
Hollow metallic nanostructures have shown potential in various applications including catalysis, drug delivery and phototherapy, owing to their large surface areas, reduced net density, and unique optical properties. In this study, novel hollow gold nanoflowers (HAuNFs) consisting of an open hollow channel in the center and multiple branches/tips on the outer surface are fabricated for the first time, via a facile one-step synthesis using an auto-degradable nanofiber as a bifunctional template. The one-dimensional (1D) nanofiber acts as both a threading template as well as a promoter of the anisotropic growth of the gold crystal, the combination of which leads to the formation of HAuNFs with a hollow channel and nanospikes. The synergy of favorable structural/surface features, including sharp edges, open cavity and high-index facets, provides our HAuNFs with excellent catalytic performance (activity and cycling stability) coupled with large single-particle SERS activity (including âŒ30 times of activity in ethanol electro-oxidation and âŒ40 times of single-particle SERS intensity, benchmarked against similar-sized solid gold nanospheres with smooth surfaces, as well as retaining 86.7% of the initial catalytic activity after 500 cycles in ethanol electro-oxidation). This innovative synthesis gives a nanostructure of the geometry distinct from the template and is extendable to fabricating other systems for example, hollow-channel silver nanoflowers (HAgNFs). It thus provides an insight into the design of hollow nanostructures via template methods, and offers a versatile synthetic strategy for diverse metal nanomaterials suited for a broad range of applications
OneâStep Preparation of Biocompatible Gold Nanoplates with Controlled Thickness and Adjustable Optical Properties for PlasmonâBased Applications
The ability to synthesize plasmonic nanomaterials with wellâdefined structures and tailorable size is crucial for exploring their potential applications. Gold nanoplates (AuNPLs) exhibit appealing structural and optical properties, yet their applications are limited by difficulties in thickness control. Other challenges include a narrow range of tunability in size and surface plasmon resonance, combined with a synthesis conventionally involving cytotoxic cetyltrimethylammonium (CTA) halide surfactant. Here, a oneâstep, highâyield synthesis of singleâcrystalline AuNPLs is developed, based on the combined use of two structureâdirecting agents, methyl orange and FeBr3, which undergo preferential adsorption onto different crystalline facets of gold. The obtained AuNPLs feature high shape homogeneity that enables mesoscopic selfâassembly, broadârange tunability of dimensions (controlled thickness from â7 to â20 nm, accompanied by modulation of the edge length from â150 nm to â2 ”m) and plasmonic properties. These merits, coupled with a preparation free of CTAâhalide surfactants, have facilitated the exploration of various uses, especially in bioârelated areas. For example, they are demonstrated as biocompatible photothermal agents for cell ablation in NIR I and NIR II windows. This work paves the way to the innovative fabrication of anisotropic plasmonic nanomaterials with desired attributes for wideâranging practical applications
Evaluation of Lipid-Stabilised Tripropionin Nanodroplets as a Delivery Route for Combretastatin A4
Lipid-based nanoemulsions are a cheap and elegant route for improving the delivery of hydrophobic drugs. Easy and quick to prepare, nanoemulsions have promise for the delivery of different therapeutic agents. Although multiple studies have investigated the effects of the oil and preparation conditions on the size of the nanoemulsion nanodroplets for food applications, analogous studies for nanoemulsions for therapeutic applications are limited. Here we present a study on the production of lipid-stabilised oil nanodroplets (LONDs) towards medical applications. A number of biocompatible oils were used to form LONDs with phospholipid coatings, and among these, squalane and tripropionin were chosen as model oils for subsequent studies. LONDs were formed by high pressure homogenisation, and their size was found to decrease with increasing production pressure. When produced at 175 MPa, all LONDs samples exhibited sizes between 100 â 300 nm, with polydispersity index PI between 0.1 â 0.3. The LONDs were stable for over six weeks, at 4 °C, and also under physiological conditions, showing modest changes in size (<10%). The hydrophobic drug combretastatin A4 (CA4) was encapsulated in tripropionin LONDs with an efficiency of approximately 76%, achieving drug concentration of approximately 1.3 mg/ml. SVR mouse endothelial cells treated with CA4 tripropionin LONDs showed the microtubule disruption, characteristic of drug uptake for all tested doses, which suggests successful release of the CA4 from the LONDs
The use of high-frequency ultrasound imaging and biofluorescence for in vivo evaluation of gene therapy vectors
Background: Non-invasive imaging of the biodistribution of novel therapeutics including gene therapy vectors in animal models is essential. Methods: This study assessed the utility of high-frequency ultrasound (HF-US) combined with biofluoresence imaging (BFI) to determine the longitudinal impact of a Herpesvirus saimiri amplicon on human colorectal cancer xenograft growth. Results: HF-US imaging of xenografts resulted in an accurate and informative xenograft volume in a longitudinal study. The volumes correlated better with final ex vivo volume than mechanical callipers (R = 0.7993, p = 0.0002 vs. R = 0.7867, p = 0.0014). HF-US showed that the amplicon caused lobe formation. BFI demonstrated retention and expression of the amplicon in the xenografts and quantitation of the fluorescence levels also correlated with tumour volumes.Conclusions: The use of multi-modal imaging provided useful and enhanced insights into the behaviour of gene therapy vectors in vivo in real-time. These relatively inexpensive technologies are easy to incorporate into pre-clinical studies
Developing Hollow-Channel Gold Nanoflowers as Trimodal Intracellular Nanoprobes
Gold nanoparticles-enabled intracellular surface-enhanced Raman spectroscopy (SERS) provides a sensitive and promising technique for single cell analysis. Compared with spherical gold nanoparticles, gold nanoflowers, i.e., flower-shaped gold nanostructures, can produce a stronger SERS signal. Current exploration of gold nanoflowers for intracellular SERS has been considerably limited by the difficulties in preparation, as well as background signal and cytotoxicity arising from the surfactant capping layer. Recently, we have developed a facile and surfactant-free method for fabricating hollow-channel gold nanoflowers (HAuNFs) with great single-particle SERS activity. In this paper, we investigate the cellular uptake and cytotoxicity of our HAuNFs using a RAW 264.7 macrophage cell line, and have observed effective cellular internalization and low cytotoxicity. We have further engineered our HAuNFs into SERS-active tags, and demonstrated the functionality of the obtained tags as trimodal nanoprobes for dark-field and fluorescence microscopy imaging, together with intracellular SERS
Freeze-Dried Therapeutic Microbubbles: Stability and Gas Exchange
Microbubbles (MBs) are widely used as contrast enhancement agents for ultrasound imaging and have the potential to enhance therapeutic delivery to diseases such as cancer. Yet, they are only stable in solution for a few hours to days after production, which limits their potential application. Freeze-drying provides long-term storage, ease of transport, and consistency in structure and composition, thereby facilitating their use in clinical settings. Therapeutic microbubbles (thMBs) consisting of MBs with attached therapeutic payload potentially face even greater issues for production, stability, and well-defined drug delivery. The ability to freeze-dry thMBs represents an important step for their translation to the clinic. Here, we show that it is possible to freeze-dry and reconstitute thMBs that consist of lipid-coated MBs with an attached liposomal payload. The thMBs were produced microfluidically, and the liposomes contained either calcein, as a model drug, or gemcitabine. The results show that drug-loaded thMBs can be freeze-dried and stored for at least 6 months. Upon reconstitution, they maintain their structural integrity and drug loading. Furthermore, we show that their in vivo echogenicity is maintained post-freeze-drying. Depending on the gas used in the original bubbles, we also demonstrate that the approach provides a method to exchange the gas core to allow the formulation of thMBs with different gases for combination therapies or improved drug efficacy. Importantly, this work provides an important route for the facile off-site production of thMBs that can be reformulated at the point of care
SubâNanometer Thick Gold Nanosheets as Highly Efficient Catalysts
2D metal nanomaterials offer exciting prospects in terms of their properties and functions. However, the ambient aqueous synthesis of atomicallyâthin, 2D metallic nanomaterials represents a significant challenge. Herein, freestanding and atomicallyâthin gold nanosheets with a thickness of only 0.47 nm (two atomic layers thick) are synthesized via a oneâstep aqueous approach at 20 °C, using methyl orange as a confining agent. Owing to the high surfaceâareaâtoâvolume ratio, abundance of unsaturated atoms exposed on the surface and large interfacial areas arising from their ultrathin 2D nature, the asâprepared Au nanosheets demonstrate excellent catalysis performance in the model reaction of 4ânitrophenol reduction, and remarkable peroxidaseâmimicking activity, which enables a highly sensitive colorimetric sensing of H2O2 with a detection limit of 0.11 Ă 10â6 m. This work represents the first fabrication of freestanding 2D gold with a subânanometer thickness, opens up an innovative pathway toward atomicallyâthin metal nanomaterials that can serve as model systems for inspiring fundamental advances in materials science, and holds potential across a wide region of applications
Low pH immobilizes and kills human leukocytes and prevents transmission of cell-associated HIV in a mouse model
BACKGROUND: Both cell-associated and cell-free HIV virions are present in semen and cervical secretions of HIV-infected individuals. Thus, topical microbicides may need to inactivate both cell-associated and cell-free HIV to prevent sexual transmission of HIV/AIDS. To determine if the mild acidity of the healthy vagina and acid buffering microbicides would prevent transmission by HIV-infected leukocytes, we measured the effect of pH on leukocyte motility, viability and intracellular pH and tested the ability of an acidic buffering microbicide (BufferGel(Âź)) to prevent the transmission of cell-associated HIV in a HuPBL-SCID mouse model. METHODS: Human lymphocyte, monocyte, and macrophage motilities were measured as a function of time and pH using various acidifying agents. Lymphocyte and macrophage motilities were measured using video microscopy. Monocyte motility was measured using video microscopy and chemotactic chambers. Peripheral blood mononuclear cell (PBMC) viability and intracellular pH were determined as a function of time and pH using fluorescent dyes. HuPBL-SCID mice were pretreated with BufferGel, saline, or a control gel and challenged with HIV-1-infected human PBMCs. RESULTS: Progressive motility was completely abolished in all cell types between pH 5.5 and 6.0. Concomitantly, at and below pH 5.5, the intracellular pH of PBMCs dropped precipitously to match the extracellular medium and did not recover. After acidification with hydrochloric acid to pH 4.5 for 60 min, although completely immotile, 58% of PBMCs excluded ethidium homodimer-1 (dead-cell dye). In contrast, when acidified to this pH with BufferGel, a microbicide designed to maintain vaginal acidity in the presence of semen, only 4% excluded dye at 10 min and none excluded dye after 30 min. BufferGel significantly reduced transmission of HIV-1 in HuPBL-SCID mice (1 of 12 infected) compared to saline (12 of 12 infected) and a control gel (5 of 7 infected). CONCLUSION: These results suggest that physiologic or microbicide-induced acid immobilization and killing of infected white blood cells may be effective in preventing sexual transmission of cell-associated HIV
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