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Illustration of the fluorescent ratio probe (OPDEA/BOD-NO2) with hypoxia targeting and hypoxia activation capacity for in vivo tumour imaging.

Despite the enormous advancements in nanomedicine research, a limited number of nanoformulations are available on the market, and few have been translated to clinics. An easily scalable, sustainable, and cost-effective manufacturing strategy and long-term stability for storage are crucial for successful translation. Here, we report a system and method to instantly formulate NF achieved with a nanoscale polyelectrolyte coacervate-like system, consisting of anionic pseudopeptide poly(l-lysine isophthalamide) derivatives, polyethylenimine, and doxorubicin (Dox) via simple "mix-and-go" addition of precursor solutions in seconds. The coacervate-like nanosystem shows enhanced intracellular delivery of Dox to patient-derived multidrug-resistant (MDR) cells in 3D tumor spheroids. The results demonstrate the feasibility of an instant drug formulation using a coacervate-like nanosystem. We envisage that this technique can be widely utilized in the nanomedicine field to bypass the special requirement of large-scale production and elongated shelf life of nanomaterials.

A rapid and comprehensive assessment of ischemic stroke (IS) is critical for clinicians to take the most appropriate treatment. Currently, IS assessment is mainly carried out by computed tomography (CT) and magnetic resonance imaging (MRI) in combination with observing the clinical symptoms and inquiring about contraindications. However, they cannot diagnose pathological conditions and judge the microenvironment in real-time. Near-infrared (NIR) fluorescence imaging has advantages for IS imaging, such as high sensitivity, high spatiotemporal resolution, and straightforward real-time operation. Herein, a pH-responsive fluorescent liposomal probe (BOD@Lip) was prepared for in vivo real-time visualization of the degree of IS based on the different acid microenvironments in the progression of the disease. The fluorescence imaging with BOD@Lip showed the degree of IS, and the correlation between fluorescence signals and the neurological deficit scores was established for the first time. This work provided a new method to objectively evaluate the degree of IS through a visualized route and a new insight into the relationship between the acidic microenvironment and the progression of IS. This article is protected by copyright. All rights reserved.

Tumor-selective drug delivery could enhance anticancer efficacy and avoid drug side effects. However, because of tumor heterogeneity, current nanoparticle-based drug delivery systems rarely improve clinical outcomes significantly, commonly only reducing systemic toxicity. In this work, a new tumor-specific, tyrosinase-responsive cascade amplification release nanoparticle (TR-CARN) was developed to fulfill the needs for tumor-specific drug delivery and high efficacy cancer treatment. Tyrosinase (Tyr) is specifically expressed in melanomas and can catalyze acetaminophen (APAP) to increase reactive oxygen species (ROS). It was therefore utilized here to initiate the ROS amplification procedure. In TR-CARN, a ROS-responsive prodrug BDOX was loaded into an amphiphilic polymer, and APAP was linked to the polymer through a ROS-cleavable thioether bond. TR-CARN caused reduced side effects during the delivery because of the low toxicity of BDOX. Once TR-CARN entered into the tumor, endogenous ROS triggered initial APAP and BDOX release. Tyr-mediated ROS synthesis by APAP then accelerated APAP and BDOX release and toxification. Consequently, TR-CARN achieved melanoma-specific treatment of high efficacy through the cascade amplification strategy with enhanced biosafety.

Funder: University of Cambridge WD Armstrong Trust, Funder: University of Cambridge Kurt Hahn Trust, Funder: Studienstiftung des Deutschen Volkes; funder-id: http://dx.doi.org/10.13039/501100004350, BACKGROUND: Breastfeeding is critical to health outcomes, particularly in low-resource settings where there is little access to clean water. For infants in their first twelve months of life, the delivery of medications is challenging, and use of oral syringes to deliver liquid formulations can pose both practical and emotional challenges. OBJECTIVE: To explore the potential to deliver medicine to infants via a solid formulation during breastfeeding. METHODS: Single center feasibility study within a tertiary level neonatal unit in the UK, involving twenty-six breastfeeding mother-infant dyads. A solid formulation of Vitamin B12 was delivered to infants during breastfeeding. Outcomes included the quantitative change in serum vitamin B12 and assessment of maternal expectations and experiences. RESULTS: Delivery of Vitamin B12 through a solid formulation that dissolved in human milk did not impair breastfeeding, and Vitamin B12 levels rose in all infants from a mean baseline (range) 533 pg/mL (236-925 pg/mL) to 1871 pg/mL (610-4981 pg/mL) at 6-8 hours post-delivery. Mothers described the surprising ease of 'drug' delivery, with 85% reporting a preference over the use of syringes. CONCLUSIONS: Solid drug formulations can be delivered during breastfeeding and were preferred by mothers over the delivery of liquid formulations via a syringe.

Spinal cord injury (SCI) is one of the most debilitating injuries, and transplantation of stem cells in a scaffold is a promising strategy for treatment. However, stem cell treatment of SCI has been severely impaired by the increased generation of reactive oxygen species in the lesion microenvironment, which can lead to a high level of stem cell death and dysfunction. Herein, a MnO

Cornea diseases are a leading cause of blindness and the disease burden is exacerbated by the increasing shortage around the world for cadaveric donor corneas. Despite the advances in the field of regenerative medicine, successful transplantation of laboratory made artificial corneas has not been fully realised in clinical practice. The causes of failure of such artificial corneal implants are multifactorial and include latent infections from viruses and other micorbes, enzyme over-expression, implant degradation, extrusion or delayed epithelial regeneration. Therefore, there is an urgent unmet need for developing customized corneal implants to suit the host environment, counter the effects of inflammation or infection and that are able to track early signs of implant failurein situ. In the present work, we describe a nano toolbox comprising tools for drug release and in addition capable of being infection responsive, promoting regeneration including non-invasive monitoring ofin situcorneal environment. These nano constructs can be incorporated within pro-regenerative biosynthetic implants, transforming them into theranostic devices able to respond to biological changes following implantation.

Glycerol and trehalose are widely used protective agents in the cryopreservation of red blood cells (RBCs). This chapter presents a protocol for use of these agents as cryoprotectants of RBCs, with post-thaw assessment of cell survival and cellular oxidative-reductive status. The main aim is to provide a framework for further studies aimed at improving RBC survival and function and to supply improved biomaterials for studies on RBC biochemistry, major operations, as well as those for urgent use in emergency room situations.

The current trend in industrial biotechnology is to move from batch or fed‐batch fermentations to continuous operations. The success of this transition will require the development of genetically stable production strains, the use of strong constitutive promoters, and the development of new medium formulations that allow an appropriate balance between cell growth and product formation. We identified genes that showed high expression in Komagataella phaffii during different steady‐state conditions and explored the utility of promoters of these genes (Chr1–4_0586 and FragB_0052) in optimizing the expression of two different r‐proteins, human lysozyme (HuLy), and the anti‐idiotypic antibody fragment, Fab‐3H6, in comparison with the widely used glyceraldehyde‐3‐phosphate dehydrogenase promoter. Our results showed that the promoter strength was highly dependent on the cultivation conditions and thus constructs should be tested under a range of conditions to determine both the best performing clone and the ideal promoter for the expression of the protein of interest. An important benefit of continuous production is that it facilitates the use of the genome‐scale metabolic models in the design of strains and cultivation media. In silico flux distributions showed that production of either protein increased the flux through aromatic amino acid biosynthesis. Tyrosine supplementation increased the productivity for both proteins, whereas tryptophan addition did not cause any significant change and, phenylalanine addition increased the expression of HuLy but decreased that of Fab‐3H6. These results showed that a genome‐scale metabolic model can be used to assess the metabolic burden imposed by the synthesis of a specific r‐protein and then this information can be used to tailor a cultivation medium to increase production.

An in vitro simulation system was developed to study the effect of an infant's peristaltic tongue motion during breastfeeding on oral rapidly disintegrating tablets in the mouth, for use in rapid product candidate screening. These tablets are being designed for use inside a modified nipple shield worn by a mother during breastfeeding, a proposed novel platform technology to administer drugs and nutrients to breastfeeding infants. In this study, the release of a model compound, sulforhodamine B, from tablet formulations was studied under physiologically relevant forces induced by compression and rotation of a tongue mimic. The release profiles of the sulforhodamine B in flowing deionized water were found to be statistically different using 2-way ANOVA with matching, when tongue mimic rotation was introduced for 2 compression levels representing 2 tongue strengths (p = 0.0013 and p < 0.0001 for the lower and higher compression settings, respectively). Compression level was found to be a significant factor for increasing model compound release at rotational rates representing nonnutritive breastfeeding (p = 0.0162). This novel apparatus is the first to simulate the motion and pressures applied by the tongue and could be used in future infant oral product development.

With the cell therapy industry continuing to grow, the ability to preserve clinical grade cells, including mesenchymal stem cells (MSCs), whilst retaining cell viability and function remains critical for the generation of off-the-shelf therapies. Cryopreservation of MSCs, using slow freezing, is an established process at lab scale. However, the cytotoxicity of cryoprotectants, like Me

The affinity isolation of pre-purified plasmid DNA (pDNA) from model buffer solutions using native and poly(ethylene glycol) (PEG) derivatized zinc finger-GST (Glutathione-S-Transferase) fusion protein was examined in PEG-dextran (DEX) aqueous two-phase systems (ATPSs). In the absence of pDNA, partitioning of unbound PEGylated fusion protein into the PEG-rich phase was confirmed with 97.5% of the PEGylated fusion protein being detected in the PEG phase of a PEG 600-DEX 40 ATPS. This represents a 1322-fold increase in the protein partition coefficient in comparison to the non-PEGylated protein (Kc = 0.013). In the presence of pDNA containing a specific oligonucleotide recognition sequence, the zinc finger moiety of the PEGylated fusion protein bound to the plasmid and steered the complex to the PEG-rich phase. An increase in the proportion of pDNA that partitioned to the PEG-rich phase was observed as the concentration of PEGylated fusion protein was increased. Partitioning of the bound complex occurred to such an extent that no DNA was detected by the picogreen assay in the dextran phase. It was also possible to partition pDNA using a non-PEGylated (native) zinc finger-GST fusion protein in a PEG 1000-DEX 500 ATPS. In this case the native ligand accumulated mainly in the PEG phase. These results indicate good prospects for the design of new plasmid DNA purification methods using fusion proteins as affinity ligands.

Amphipathic pH-responsive polymers have shown to increase the permeability of cell membranes to trehalose hence improving the cryopreservation of mammalian cells. However, the trafficking of both the polymer and trehalose across the cell membrane has not yet been thoroughly analysed. The objective of this study was to investigate the effect on cryopreservation of the trafficking of the disaccharide trehalose along PP-50, an amphipathic polymer, through an osteosarcoma cell line (SAOS-2). Confocal microscopy analysis confirmed the presence of intracellular labelled trehalose only when incubated in the presence of PP-50. Further analysis confirmed that both trehalose and PP-50 localised in the cytoplasm, accumulated mainly in the perinuclear area. Quantitative analysis of the colocalisation between trehalose and PP-50 showed Pearson and Manders coefficients of 0.862 ± 0.008 and 0.766 ± 0.033, respectively, suggesting a high degree of intracellular colocalisation between these molecules. Cryopreserved cells pre-incubated with trehalose and PP-50 showed increased cryosurvival when compared with cells pre-incubated in the absence of the polymer. PP-50 showed to be directly involved in the uptake of trehalose, a critical characteristic towards use in cryopreservation and biomedical applications.

We have shown previously that a sequence-specific DNA-binding protein based on the Lac repressor protein can isolate pre-purified DNA efficiently from simple buffer solution but our attempts to purify plasmids directly from crude starting materials were disappointing with unpractically low DNA yields. We have optimized tbe procedure and present a simple affinity methodology whereby plasmid DNA is purified directly by mixing two crude cell lysates, one cell lysate containing the plasmid and the other the protein affinity ligand, without the need for treatment by RNaseA. After IMAC chromatography, high purity supercoiled DNA is recovered in good yields of 100-150 μg plasmid per 200 mL shake flask culture. Moreover, the resulting DNA is free from linear or open-circular plasmid DNA, genomic DNA, RNA, and protein, to the limits of our detection. Furthermore, we show that lyophilized affinity ligand can be stored at room temperature and re-hydrated for use when required. © 2007 Wiley Periodicals, Inc.

We report the encapsulation of the hydrophilic model molecule calcein in the Zr-based MOF UiO-66, followed by amorphization of the framework by ball-milling. We show controlled release of calcein over more than 30 days, compared with the 2 day release period from crystalline UiO-66.

A micro-capillary film has been developed that offers the potential for an at-line analytical tool for rapid aggregate analysis during biopharmaceutical antibody production. A non-porous walled micro-capillary film (NMCF) with cation exchange functionality was demonstrated to act as a chromatography medium that could be operated with high linear fluid velocities and was highly resistant to blockage by entrained particulates, including cells. The NMCF containing 19 parallel microcapillaries was prepared using a melt extrusion process from poly(ethylene-vinyl alcohol) copolymer (EVOH). The NMCF-EVOH was modified to have cation-exchange functionality (NMCF-EVOH-SP) and shown to differentially bind monomer and aggregated species of IgG antibody directly from a bioreactor. The use of NMCF-EVOH-SP to quantify aggregate concentrations in monoclonal antibody preparations in less than 20 minutes was demonstrated.

Carbon nanotube salts prepared by treating single-wall carbon nanotubes (SWNTs) with lithium in liquid ammonia react with ω-bromocarboxylic acids to yield sidewall-derivatized SWNTs. These can be reacted with amine-terminated polyethyleneglycol (PEG) chains (e.g., H2N−mPEG−OMe, MW = 5000 Da) to yield water-soluble PEGylated SWNTs. Short nanotubes (average length ∼ 60 nm) functionalized by PEGylation of the carboxylic acid groups at the end of the nanotubes exhibit greater solubility in water than the longer (average length ∼ 300 nm) sidewall-PEGylated pristine nanotubes.

Current approaches for purifying plasmids from bacterial production systems exploit the physiochemical properties of nucleic acids in non-specific capture systems. In this study, an affinity system for plasmid DNA (pDNA) purification has been developed utilizing the interaction between the lac operon (lacO) sequence contained in the pDNA and a 64mer synthetic peptide representing the DNA-binding domain of the lac repressor protein, LacI. Two plasmids were evaluated, the native pUC19 and pUC19 with dual lacO3/lacOs operators (pUC19lacO3/lacOs), where the lacOs operator is perfectly symmetrical. The DNA-protein affinity interaction was evaluated by surface plasmon resonance using a Biacore system. The affinity capture of DNA in a chromatography system was evaluated using LacI peptide that had been immobilized to Streamline™ adsorbent. The KD-values for double stranded DNA (dsDNA) fragments containing lacO1 and lacO3 and lacOs and lacO3 were 5.7 ± 0.3 × 10 -11 M and 4.1 ± 0.2 × 10-11 M respectively, which compare favorably with literature reports of 5 × 10-10 - 1 × 10-9 M for native laCO1 and 1-1.2 × 10-10 M for lacO1 in a saline buffer. Densitometric analysis of the gel bands from the affinity chromatography run clearly showed a significant preference for capture of the supercoiled fraction from the feed pDNA sample. The results indicate the feasibility of the affinity approach for pDNA capture and purification using native protein-DNA interaction. © 2006 Wiley Periodicals, Inc.

The development of a protein-mediated dual functional affinity adsorption of plasmid DNA is described in this work. The affinity ligand for the plasmid DNA comprises a fusion protein with glutathione-S-transferase (GST) as the fusion partner with a zinc finger protein. The protein ligand is first bound to the adsorbent by affinity interaction between the GST moeity and gluthathione that is covalently immobilized to the base matrix. The plasmid binding is then enabled via the zinc finger protein and a specific nucleotide sequence inserted into the DNA. At lower loadings, the binding of the DNA onto the Fractogel, Sepharose, and Streamline matrices was 0.0078 +/- 0.0013, 0.0095 +/- 0.0016, and 0.0080 +/- 0.0006 mg, respectively, to 50 microL of adsorbent. At a higher DNA challenge, the corresponding amounts were 0.0179 +/- 0.0043, 0.0219 +/- 0.0035, and 0.0190 +/- 0.0041 mg, respectively. The relatively constant amounts bound to the three adsorbents indicated that the large DNA molecule was unable to utilize the available zinc finger sites that were located in the internal pores and binding was largely a surface adsorption phenomenon. Utilization of the zinc finger binding sites was shown to be highest for the Fractogel adsorbent. The adsorbed material was eluted with reduced glutathione, and the eluted efficiency for the DNA was between 23% and 27%. The protein elution profile appeared to match the adsorption profiles with significantly higher recoveries of bound GST-zinc finger protein.

The use of small interfering RNAs (siRNAs) to down-regulate the expression of disease-associated proteins carries significant promise for the treatment of a variety of clinical disorders. One of the main barriers to the widespread clinical use of siRNAs, however, is their entrapment and degradation within the endolysosomal pathway of target cells. Here we report the trafficking and function of PP75, a non-toxic, biodegradable, lipid membrane disruptive anionic polymer composed of phenylalanine derivatized poly(L-lysine iso-phthalamide). PP75 is readily endocytosed by cells, safely permeabilizes endolysosomes in a pH dependent manner and facilitates the transfer of co-endocytosed materials directly into the cytoplasm. The covalent attachment of siRNAs to PP75 using disulfide linkages generates conjugates that effectively traffic siRNAs to the cytoplasm of target cells both in vitro and in vivo. In a subcutaneous malignant glioma tumor model, a locally delivered PP75-stathmin siRNA conjugate decreases stathmin expression in tumor cells and, in combination with the nitrosourea chemotherapy carmustine, is highly effective at inhibiting tumor growth. PP75 may be clinically useful for the local delivery of siRNAs, in particular for the treatment of solid tumors.

The preparation, characterisation and testing of stable non-porous coated perfluorocarbon supports functionalised with the metal chelate, iminodiacetic acid (IDA) is described. Polyvinyl alcohol (PVA), a neutral hydrophilic polymer was esterified with perfluorooctanoyl chloride and anchored to the surface of solid perfluorocarbon particles through multiple fluorophilic interactions. The PVA-coated particles were then activated by epoxidation and coupled with IDA. The presence of surface-attached chelates was clearly demonstrated by the binding and selective desorption of Zn2+ ions. Three particulate perfluorocarbons were selected as potential starting materials and the conditions for preparation of metal chelating adsorbents optimised with respect to ease of manufacture, ligand density and binding capacity towards a monoclonal antibody known to bind to commercial Zn(2+)-IDA supports. The choice of base particle strongly influenced the ligand densities and specific binding capacities towards the monoclonal antibody that could be achieved under optimal preparative conditions. Possible ways in which these metal chelating adsorbents may be employed to recover the monoclonal antibody directly from culture vessels are discussed.

Magnetic cell labeling has numerous applications in cell separation and sorting, tissue engineering and magnetic resonance imaging. Mammalian cells can be magnetically labeled by first biotinylating their cell membrane proteins and then binding streptavidin‐coated paramagnetic particles onto the biotinylated proteins. Characterization studies indicated that the extent of cell biotinylation could be controlled by varying the biotinylating reagent concentration. Since the paramagnetic particles have high mass magnetization, the labeled cells were very responsive to magnetic field gradients and they could be targeted and patterned precisely using magnets. Magnetic multicellular spheroids were generated from these labeled cells and the constituent cells were found to be viable. These spheroids could be patterned using magnetic fields in a few seconds. This cell labeling methodology can be adapted to a wide variety of mammalian cell types. The labeled cells can then be manipulated in two dimensional cell cultu...

The DNA binding fusion protein, LacI-His6-GFP, together with the conjugate PEG-IDA-Cu(II) (10 kDa) was evaluated as a dual affinity system for the pUC19 plasmid extraction from an alkaline bacterial cell lysate in poly(ethylene glycol) (PEG)/dextran (DEX) aqueous two-phase systems (ATPS). In a PEG 600-DEX 40 ATPS containing 0.273 nmol of LacI fusion protein and 0.14% (w/w) of the functionalised PEG-IDA-Cu(II), more than 72% of the plasmid DNA partitioned to the PEG phase, without RNA or genomic DNA contamination as evaluated by agarose gel electrophoresis. In a second extraction stage, the elution of pDNA from the LacI binding complex proved difficult using either dextran or phosphate buffer as second phase, though more than 75% of the overall protein was removed in both systems. A maximum recovery of approximately 27% of the pCU19 plasmid was achieved using the PEG-dextran system as a second extraction system, with 80-90% of pDNA partitioning to the bottom phase. This represents about 7.4 microg of pDNA extracted per 1 mL of pUC19 desalted lysate.

Lyophilization is the most popular method for achieving improved stability of labile biopharmaceuticals, but a significant fraction of product activity can be lost during processing due to stresses that occur in both the freezing and the drying stages. The effect of the freezing rate on the recovery of herpes simplex virus 2 (HSV-2) infectivity in the presence of varying concentrations of cryoprotectant excipients is reported here. The freezing conditions investigated were shelf cooling (223 K), quenching into slush nitrogen (SN2), and plunging into melting propane cooled in liquid nitrogen (LN2). The corresponding freezing rates were measured, and the ice crystal sizes formed within the samples were determined using scanning electron microscopy (SEM). The viral activity assay demonstrated the highest viral titer recovery for nitrogen cooling in the presence of low (0.25% w/v sucrose) excipient concentration. The loss of viral titer in the sample cooled by melting propane was consistently the highest among those results from the alternative cooling methods. However, this loss could be minimized by lyophilization at lower temperature and higher vacuum conditions. We suggest that this is due to a higher ratio of ice recrystallization for the sample cooled by melting propane during warming to the temperature at which freeze-drying was carried out, as smaller ice crystals readily enlarge during warming. Under the same freezing condition, a higher viral titer recovery was obtained with a formulation containing a higher concentration of sugar excipients. The reason was thought to be twofold. First, sugars stabilize membranes and proteins by hydrogen bonding to the polar residues of the biomolecules, working as a water substitute. Second, the concentrated sugar solution lowers the nucleation temperature of the water inside the virus membrane and prevents large ice crystal formation within both the virus and the external medium.

The reaction rates of ground-state OH radicals, X2Π(v″= 0), with the molecules CH4, CO, HCl, DCl, HBr and DBr have been investigated in the gas phase by time-resolved resonance fluorescence at λ= 307 nm [OH(A2∑+–X2Π, (0, 0)]. The OH radicals were generated photochemically by the repetitive vacuum ultraviolet photolysis of water vapour in a flow system, kinetically equivalent to a static system, using a high-intensity, magnetically pinched pulsed light source, and optically excited to the A2∑+ state by means of a resonance source operating in the standard orthogonal arrangement. The resulting time-resolved resonance fluorescence signals were monitored by means of a highly sensitive detection system employing pre-trigger photomultiplier gating, photon counting and signal averaging. Absolute second-order rate constants (k/cm3 molecule–1 s–1, 300 K) were obtained for the reactions of OH with the above molecules as follows: CH4(7.66 ± 0.64)× 10–15 CO (1.46 ± 0.12)× 10–13, HCl(6.66 ± 0.52)× 10–13, DCl (3.48 ± 0.30)× 10–13, HBr (6.01 ± 0.32)× 10–12 and DBr (2.05 ± 0.14)× 10–12, the quoted errors being 2σ. The rate constants for CH4 and CO constituted a kinetic test of the system, being in accord with accepted values for these quantities. The data for the hydrogen halides are compared, where possible, with previously determined rates obtained from monitoring OH directly by various methods. To the best of our knowledge, the absolute rate constant for the reaction with DBr has not been reported hitherto from direct monitoring of OH.

Ground state antimony atoms, Sb[5p3(4S)], have been studied by time-resolved resonance fluorescence at λ= 231.1 nm (64P½→ 54S) in the “single-shot” mode. The antimony atoms were generated by pulsed irradiation of SbMe3 using a “magnetically-pinched”, Garton light source with a high spectral output in the vacuum ultraviolet. Optical excitation of the resulting Sb(54S) was effected by means of a sealed microwave-powered atomic emission source, and the resonance fluorescence was monitored photoelectrically with a photomultiplier tube gated with a “pre-trigger” system. Kinetic studies of Sb(54S) in the presence of NO and of O2 are described and the resulting rate constants are compared with analogous data derived previously using time-resolved resonance absorption at the same wavelength, and discussed in terms of departures from the standard Beer–Lambert law for light absorption. Radiation trapping calculations are also described which involve summation of the Voigt profiles over all the individual nuclear hyperfine components that contribute to the λ= 231.1 nm transition. Solutions of the diffusion equation for radiation with different boundary conditions are employed in the calculations of the relationship between fluorescence intensity and particle density. The results are compared with the experimental fluorescence intensity calibration for this system.

We present a kinetic study of ground state arsenic atoms, generated photochemically and monitored by fluorescence in the time-resolved mode following optical excitation. As[4p3(4S)] was derived from the repetitive pulsed irradiation of low pressures of either AsMe3 or AsCl3, in the presence of excess helium, in a flow system which is kinetically equivalent to a static system. The transient atoms were then monitored photoelectrically by summation of the optically excited fluorescence, principally at the wavelengths λ= 189.04, 193.76 and 197.76 and 197.23 nm [4p25s(4P5/2, , ½)→ 4p3(4S), respectively] using a “pre-trigger” photomultiplier gating system coupled with singal averaging. The decay of the arsenic atoms in the presence of the added reactant gases O2, Cl2, NO and C2H4 is described, for which second-order reaction rate constants are reported. These data are compared with previous results derived from time-resolved resonance absorption studies at λ= 189.04 nm. The two sets of rate constants resulting from the resonance absorption fluorescence and absorption studies are then employed in order to discuss the modified Beer–Lambert Law, Itr=I0 exp [–Iµ(cl)γ], that has been used in the resonance absorption measurements. Finally, we present a model radiation trapping calculation including the effects of nuclear hyperfine interaction using the diffusion theory of radiation for the three wavelengths monitored in fluorescence, and calculate the relationship between fluorescence intensity and particle density. This is compared with empirical measurements of the fluorescence intensity against particle density calibration.

The temporal behaviour of ground state phosphorus atoms, P[3p3(4S)], generated by repetitive pulsed irradiation in a flow system, has been studied by time-resolved resonance fluorescence. P(34S) was generated photochemically from PCI3 in the presence of excess helium buffer gas and optically excited by means of the emission from a microwave-powered atomic spectroscopic source. The total resonance fluorescence in the vacuum ultraviolet from the systems P[3p24s(4P½,,5/2)→ 3p3(4S)](λ= 178.77, 178.29 and 177.50 nm, respectively) and P[3p4(4P5/2,,½)→ 3p3(4S)](λ= 167.97, 167.46 and 167.17 nm, respectively) was monitored photoelectrically and the signal-averaged results employed to characterise the kinetic decay of the phosphorus atom in the presence of various added gases. An empirical calibration of the relationship between the fluorescence intensity and the relative particle density of P(34S) was established and the linear region employed for kinetic study. Second-order rate constants (kR, cm3 molecule–1 s–1, 300 K) are reported for the reaction of P(34S) with the following gases: O2(2.1 ± 0.3 × 10–12), Cl2(3.4 ± 0.3 × 10–12), NO (5.3 ± 0.5 × 10–13), C2H2(1.2 ± 0.1 × 10–13), C2H4(6.8 ± 0.8 × 10–13) and PCl3(1.7 ± 0.3 × 10–12). These data are compared with previous results obtained by time-resolved resonance line absorption and used to consider further the modified Beer–Lambert law, Itr=I0 exp [–Iµ(cl)γ] used in the resonance absorption measurements. Finally, radiation trapping calculations are described for the systems P[3p24s(4PJ)] and P[3p4(4PJ)]→ P[(34S)] using the diffusion theory of radiation. Line shapes employing the summation of Voigt profiles for all the nuclear hyperfine components contributing to a given electronic transition are used. The calculated relationships between the fluorescence intensity and P[(34S)] for various boundary conditions of the diffusion equation are compared with the empirical calibration.

Ground state nitrogen atoms, N(24S), generated by pulsed photochemical initiation, have been, studied by time-resolved resonance fluorescence following optical excitation in the vacuum ultraviolet, λ= 120 nm, N[2p,23s(4P½,,[graphic omitted])→ 2p3(4S)]. Atomic nitrogen, principally in the optically metastable doublet states, N[2p3(2DJ, 2PJ)], was produced by the repetitive vacuum ultraviolet photolysis of N2O and collisionally quenched to the 4S state by the use of N2 as a buffer gas. Photoelectric detection of the vacuum u.v. signals employed photon counting coupled with signal summation in a multiscalar. Considerable care was required to eliminate spurious photon signals at λ= 130 nm due to O(23PJ)[O(33S1)→ O(23PJ)]. Absolute rate data for the collisional removal of N(24S) in the presence of the gases NO, NO2, O3 and C2H4 are presented and compared with previously reported data. The results for N + C2H4 are further discussed in relation to the “HCN limiting yield” method that has been employed hitherto as a marker for N atom kinetics.

We describe a kinetic investigation of H and D atoms in their electronic ground states by the method of time-resolved Lyman-α resonance fluorescence in the vacuum ultraviolet following pulsed photochemical generation of the atoms. The method involved repetitive pulsing, photon counting and signal averaging. Absolute rate constants (k/cm3 molecule–1 s–1, 300 K) are reported for the following reactants; H + H2S, (8.6 ± 0.5)× 10–13; D + D2S, (7.9 ± 0.4)× 10–13; H + HBr, (6.0 ± 0.1)× 10–12; D + HBr, (4.1 ± 0.1)× 10–12; H + DBr, (4.7 ± 0.1)× 10–12; D + DBr, (2.7 ± 0.1)× 10–12. The rates for the reactions with HBr and DBr are compared with values previously derived from e.p.r. measurements on H and D in a flow discharge system.

Cornea diseases are a leading cause of blindness and the disease burden is exacerbated by the increasing shortage around the world for cadaveric donor corneas. Despite the advances in the field of regenerative medicine, successful transplantation of laboratory‐made artificial corneas is not fully realized in clinical practice. The causes of failure of such artificial corneal implants are multifactorial and include latent infections from viruses and other microbes, enzyme overexpression, implant degradation, extrusion or delayed epithelial regeneration. Therefore, there is an urgent unmet need for developing customized corneal implants to suit the host environment and counter the effects of inflammation or infection, which are able to track early signs of implant failure in situ. This work reports a nanotoolbox comprising tools for protection from infection, promotion of regeneration, and noninvasive monitoring of the in situ corneal environment. These nanosystems can be incorporated within pro‐regenerative biosynthetic implants, transforming them into theranostic devices, which are able to respond to biological changes following implantation. Funding agencies: EU H2020 Marie Sklodowska-Curie Individual Fellowship [706694]; MIIC Strategic Postdoc Grant; MIIC Seed Grant at Linkoping University (LiU), Sweden