In the last decade, extracellular vesicles (EVs) have emerged as a key cell-free strategy for the treatment of a range of pathologies, including cancer, myocardial infarction and inflammatory diseases. Indeed, the field is rapidly transitioning from promising in vitro reports towards in vivo animal models and early clinical studies. These investigations exploit the high physicochemical stability and biocompatibility of EVs, as well as their innate capacity to communicate with cells over long distances via signal transduction and membrane fusion. This review will focus on methods in which EVs can be chemically or biologically modified to broaden, alter or enhance their therapeutic capability. We will examine two broad strategies, which have been used to introduce a wide range of nanoparticles, reporter systems, targeting peptides, pharmaceutics and functional RNA molecules. First, we will explore how EVs can be modified by manipulating their parent cells; either through genetic or metabolic engineering, or by introducing exogenous material that is subsequently incorporated into secreted EVs. Second, we consider how EVs can be directly functionalized using strategies such as hydrophobic insertion, covalent surface chemistry and membrane permeabilization. We will discuss the historical context of each specific technology, present prominent examples and evaluate the complexities, potential pitfalls and opportunities presented by different re-engineering strategies. KeywordsExtracellular Vesicles; Exosomes; Microvesicles; Functionalization; Genetic Manipulation; Drug Loading; Membrane Modification; Cell-Free Therapy Extracellular Vesicles: Cell-Derived Nanovectors Extracellular vesicles (EVs) are a collective of small, naturally-derived particles, which, until recently, represented an overlooked and underappreciated component of the cellular secretome. Three major categories of EV have been defined, predominantly based upon vesicle biogenesis, but with notable differences in size and composition.1,2 Exosomes are formed when the peripheral membrane of multivesicular bodies (MVBs) undergo reverse budding to form small nanovesicles (30-100 nm in diameter) that are released when MVBs fuse with the cytoplasmic membrane.3 Microvesicles are larger in size (c.f. 100-1000 nm) * m.stevens@imperial.ac.uk. Europe PMC Funders GroupAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2017 September 19.Published in final edited form as: ACS Nano. 2017 January 24; 11(1): 69-83. doi:10.1021/acsnano.6b07607. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts and are produced during shedding or budding of the cytoplasmic membrane.4 Exosomes and microvesicles are produced by healthy cells as part of regular membrane turnover and exocytosis. In contrast, apoptotic bodies (c.f. 500-2000 nm) are generated from outward membrane blebbing in cells undergoing apoptosis.5 Apoptotic bodies, microvesicles and exosomes are each enclosed by a phospholipid membrane bilayer, comparable to the cytoplasmic mem...

We present the main findings of the 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia (AAGA). Incidences were estimated using reports of accidental awareness as the numerator, and a parallel national anaesthetic activity survey to provide denominator data. The incidence of certain/probable and possible accidental awareness cases was ~1:19,600 anaesthetics (95% confidence interval 1:16,700-23,450). However, there was considerable variation across subtypes of techniques or subspecialities. The incidence with neuromuscular block (NMB) was ~1:8200 (1:7030-9700), and without, it was ~1:135,900 (1:78,600-299,000). The cases of AAGA reported to NAP5 were overwhelmingly cases of unintended awareness during NMB. The incidence of accidental awareness during Caesarean section was ~1:670 (1:380-1300). Two-thirds (82, 66%) of cases of accidental awareness experiences arose in the dynamic phases of anaesthesia, namely induction of and emergence from anaesthesia. During induction of anaesthesia, contributory factors included: use of thiopental, rapid sequence induction, obesity, difficult airway management, NMB, and interruptions of anaesthetic delivery during movement from anaesthetic room to theatre. During emergence from anaesthesia, residual paralysis was perceived by patients as accidental awareness, and commonly related to a failure to ensure full return of motor capacity. One-third (43, 33%) of accidental awareness events arose during the maintenance phase of anaesthesia, mostly due to problems at induction or towards the end of anaesthesia. Factors increasing the risk of accidental awareness included: female sex, age (younger adults, but not children), obesity, anaesthetist seniority (junior trainees), previous awareness, out-of-hours operating, emergencies, type of surgery (obstetric, cardiac, thoracic), and use of NMB. The following factors were not risk factors for accidental awareness: ASA physical status, race, and use or omission of nitrous oxide. We recommend that an anaesthetic checklist, to be an integral part of the World Health Organization Safer Surgery checklist, is introduced as an aid to preventing accidental awareness. This paper is a shortened version describing the main findings from NAP5--the full report can be found at http://www.nationalauditprojects.org.uk/NAP5_home.

pK(a) values of 19.8-28.2 are reported for the conjugate acids of a large series of NHCs in water. The effects of ring size, N-substituent and C(4)-C(5) saturation on pK(a) are discussed.

A major challenge in three-dimensional (3D) bioprinting is the limited number of bioinks that fulfill the physicochemical requirements of printing while also providing a desirable environment for encapsulated cells. Here, we address this limitation by temporarily stabilizing bioinks with a complementary thermo-reversible gelatin network. This strategy enables the effective printing of biomaterials that would typically not meet printing requirements, with instrument parameters and structural output largely independent of the base biomaterial. This approach is demonstrated across a library of photocrosslinkable bioinks derived from natural and synthetic polymers, including gelatin, hyaluronic acid, chondroitin sulfate, dextran, alginate, chitosan, heparin, and poly(ethylene glycol). A range of complex and heterogeneous structures are printed, including soft hydrogel constructs supporting the 3D culture of astrocytes. This highly generalizable methodology expands the palette of available bioinks, allowing the biofabrication of constructs optimized to meet the biological requirements of cell culture and tissue engineering.

Bioprinting is an emerging technique for the fabrication of living tissues that allows cells to be arranged in predetermined three-dimensional (3D) architectures. However, to date, there are limited examples of bioprinted constructs containing multiple cell types patterned at high-resolution. Here we present a low-cost process that employs 3D printing of aqueous droplets containing mammalian cells to produce robust, patterned constructs in oil, which were reproducibly transferred to culture medium. Human embryonic kidney (HEK) cells and ovine mesenchymal stem cells (oMSCs) were printed at tissue-relevant densities (107 cells mL−1) and a high droplet resolution of 1 nL. High-resolution 3D geometries were printed with features of ≤200 μm; these included an arborised cell junction, a diagonal-plane junction and an osteochondral interface. The printed cells showed high viability (90% on average) and HEK cells within the printed structures were shown to proliferate under culture conditions. Significantly, a five-week tissue engineering study demonstrated that printed oMSCs could be differentiated down the chondrogenic lineage to generate cartilage-like structures containing type II collagen.