Interactions between callose and cellulose revealed through the analysis of biopolymer mixtures.

The properties of (1,3)-β-glucans (i.e., callose) remain largely unknown despite their importance in plant development and defence. Here we use mixtures of (1,3)-β-glucan and cellulose, in ionic liquid solution and hydrogels, as proxies to understand the physico-mechanical properties of callose. We show that after callose addition the stiffness of cellulose hydrogels is reduced at a greater extent than predicted from the ideal mixing rule (i.e., the weighted average of the individual components' properties). In contrast, yield behaviour after the elastic limit is more ductile in cellulose-callose hydrogels compared with sudden failure in 100% cellulose hydrogels. The viscoelastic behaviour and the diffusion of the ions in mixed ionic liquid solutions strongly indicate interactions between the polymers. Fourier-transform infrared analysis suggests that these interactions impact cellulose organisation in hydrogels and cell walls. We conclude that polymer interactions alter the properties of callose-cellulose mixtures beyond what it is expected by ideal mixing

Characterisation of Liposome-Loaded Microbubble Populations for Subharmonic Imaging

Therapeutic microbubbles could make an important contribution to the diagnosis and treatment of cancer. Acoustic characterisation was performed on microfluidic generated microbubble populations that either were bare or had liposomes attached. Through the use of broadband attenuation techniques (3–8 MHz), the shell stiffness was measured to be 0.72 ± 0.01 and 0.78 ± 0.05 N/m and shell friction was 0.37 ± 0.05 and 0.74 ± 0.05 × 10−6 kg/s for bare and liposome-loaded microbubbles, respectively. Acoustic scatter revealed that liposome-loaded microbubbles had a lower subharmonic threshold, occurring from a peak negative pressure of 50 kPa, compared with 200 kPa for equivalent bare microbubbles. It was found that liposome loading had a negligible effect on the destruction threshold for this microbubble type, because at a mechanical index >0.4 (570 kPa), 80% of both populations were destroyed

Dataset associated with "Influence of intercalating perfluorohexane into the lipid shell on nano and microbubbles stability"

The data presented here supports the images presented in the manuscript to clarify the effect of incorporating perfluorohexane into the microbubble. Briefly: Microbubbles have potential diagnostic and therapeutic agents. In vivo stability is important with the bubbles required to survive multiple passages through heart and lungs to permit 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 important role in improving microbubble stability, we show that inclusion of small quantities of C6F14 in the microbubble bolus significantly improves lifetime. Our results indicate that the C6F14 inserts into lipid shell, decreasing surface tension, to 19 mN/m, and increasing shell resistance, as well as saturating the surrounding medium. Surface area isotherms suggest that C6F14 incorporates into the acyl chain region of the lipid, at high molar ratio indicating ~2 perfluorocarbon molecule per 5 lipid molecules. The resulting microbubble boluses exhibit higher in vivo image intensity, compared to the commercial compositions as well as longer lifetimes

Research Spotlight: Microbubbles for Therapeutic Delivery

Systemic injection of chemotherapy agents for treating cancer can cause severe side effects for the patient, as well as being a relatively inefficient use of expensive and highly toxic drugs. The area of targeted drug delivery in which drugs are delivered utilizing a specialized carrier directly to the cancerous tumor via immuno-recognition has gained much interest in recent years. Such an approach reduces the side effects of systemic injection and also provides a localized, high-concentration treatment directly to the cancer. Our group at the University of Leeds (Leeds, UK) is developing therapeutic microbubbles that double as both agents for contrast-enhanced ultrasound imaging and drug-delivery vehicles that are targeted to specific cancer cell receptors. Ultimately, a large amplitude sound wave will be used to destroy the bubbles and trigger release of the drug at the targeted tumor. Theranostic microbubbles are a simple and versatile drug-delivery technique that could potentially improve cancer treatment, both in terms of patient experience and overall drug efficiency. Importantly, they offer new ways of delivering hydrophobic drugs, which have traditionally been difficult to deliver efficiently

Nanomechanics of Lipid Encapsulated Microbubbles with Functional Coatings

Microbubbles (MBs) are increasingly being proposed as delivery vehicles for targeted therapeutics, as well as being contrast agents for ultrasound imaging. MBs formed with a lipid shell are promising candidates due to their biocompatibility and the opportunity for surface functionalization, both for specific targeting of tissues and as a means to tune their mechanical response for localized ultrasound induced destruction in vivo. Herein, we acquired force-deformation data on coated lipid MBs using tip-less microcantilevers in an atomic force microscope. Model lipid MBs were designed to test the effects of adding a functional coating on the outside of the lipid leaflet, including a protein coat (streptavidin) or the addition of quantum dots (Q-dots) as optical reporters. MBs (∼3 μm diameter) were repeatedly compressed for deformations up to ∼50% to obtain a full bubble response. Addition of a coating increased the initial deformation stiffness related to shell bending ∼2-fold for streptavidin and ∼3-fold for Q-dots. The presence of a polyethylene glycol (PEG) linker in between the lipid and functional coating, led to enhanced stiffening at high deformations. The plasticity index has been determined and only those MBs that included the PEG linker showed a force dependent short time-scale (<∼1s) plasticity. This study demonstrates modulation of the mechanical response of biocompatible MBs through the addition of functional coatings necessary for rationale design of therapeutic lipid MBs for targeted drug delivery

Dataset for 'Evaluation of Lipid-Stabilised Tripropionin Nanodroplets as a Delivery Route for Combretastatin A4'

This data set corresponds to the work titled "Evaluation of Lipid-Stabilised Tripropionin Nanodroplets as a Delivery Route for Combretastatin A4", and contains data on the characterisation of LONDs, specifically sizing, concentration measurements, stability over time and appearance under TEM. Data on the encapsualtion of Combretastatin A4 in tripropionin LONDs is included, as well as in vitro work on the use of these LONDs as vehicle for the delivery of the drug in vitro

Horizon:Microfluidic platform for the production of therapeutic microbubbles and nanobubbles

Microbubbles (MBs) have a multitude of applications including as contrast agents in ultrasound imaging and as therapeutic drug delivery vehicles, with further scope for combining their diagnostic and therapeutic properties (known as theranostics). MBs used clinically are commonly made by mechanical agitation or sonication methods, which offer little control over population size and dispersity. Furthermore, clinically used MBs are yet to be used therapeutically and further research is needed to develop these theranostic agents. In this paper, we present our MB production instrument “Horizon,” which is a robust, portable, and user-friendly instrument, integrating the key components for producing MBs using microfluidic flow-focusing devices. In addition, we present the system design and specifications of Horizon and the optimized protocols that have so far been used to produce MBs with specific properties. These include MBs with tailored size and low dispersity (monodisperse); MBs with a diameter of ∼2 μm, which are more disperse but also produced in higher concentration; nanobubbles with diameters of 100-600 nm; and therapeutic MBs with drug payloads for targeted delivery. Multiplexed chips were able to improve production rates up to 16-fold while maintaining production stability. This work shows that Horizon is a versatile instrument with potential for mass production and use across many research facilities, which could begin to bridge the gap between therapeutic MB research and clinical use.</p

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 ∼2 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

Control of Director Fields in Phospholipid-Coated Liquid Crystal Droplets

In liquid crystal (LC) droplets, small changes in surface anchoring energy can produce large changes in the director field which result in readily detectable optical effects. This makes them attractive for use as biosensors. Coating LC droplets with a phospholipid monolayer provides a bridge between the hydrophobic world of LCs and the water-based world of biology and makes it possible to incorporate naturally occurring biosensor systems. However, phospholipids promote strong perpendicular (homeotropic) anchoring that can inhibit switching of the director field. We show that the tendency for phospholipid layers to promote perpendicular anchoring can be suppressed by using synthetic phospholipids in which the acyl chains are terminated with bulky tert-butyl or ferrocenyl groups; the larger these end-group(s), the less likely the system is to be perpendicular/radial. Additionally, the droplet director field is found to be dependent on the nature of the LC, particularly its intrinsic surface properties, but not (apparently) on the sign of the dielectric anisotropy, the proximity to the melting/isotropic phase transition, the surface tension (in air), or the values of the Frank elastic constants

Expanding 3D geometry for enhanced on-chip microbubble production and single step formation of liposome modified microbubbles

Micron sized, lipid stabilized bubbles of gas are of interest as contrast agents for ultra-sound (US) imaging and increasingly as delivery vehicles for targeted, triggered, therapeutic delivery. Microfluidics provides a reproducible means for microbubble production and surface functionalisation. In this study, microbubbles are generated on chip using flow-focussing microfluidic devices that combine streams of gas and liquid through a nozzle a few microns wide and then subjecting the two phases to a downstream pressure drop. While microfluidics has successfully demonstrated the generation of monodisperse bubble populations, these approaches inherently produce low bubble counts. We introduce a new micro-spray flow regime that generates consistently high bubble concentrations that are more clinically relevant compared to traditional monodisperse bubble populations. Final bubble concentrations produced by the micro-spray regime were up to 1010 bubbles mL−1. The technique is shown to be highly reproducible and by using multiplexed chip arrays, the time taken to produce one millilitre of sample containing 1010 bubbles mL−1 was ∼10 min. Further, we also demonstrate that it is possible to attach liposomes, loaded with quantum dots (QDs) or fluorescein, in a single step during MBs formation