PD-L1-PD-1 interactions limit effector regulatory T cell populations at homeostasis and during infection.

Phenotypic and transcriptional profiling of regulatory T (Treg) cells at homeostasis reveals that T cell receptor activation promotes Treg cells with an effector phenotype (eTreg) characterized by the production of interleukin-10 and expression of the inhibitory receptor PD-1. At homeostasis, blockade of the PD-1 pathway results in enhanced eTreg cell activity, whereas during infection with Toxoplasma gondii, early interferon-γ upregulates myeloid cell expression of PD-L1 associated with reduced Treg cell populations. In infected mice, blockade of PD-L1, complete deletion of PD-1 or lineage-specific deletion of PD-1 in Treg cells prevents loss of eTreg cells. These interventions resulted in a reduced ratio of pathogen-specific effector T cells: eTreg cells and increased levels of interleukin-10 that mitigated the development of immunopathology, but which could compromise parasite control. Thus, eTreg cell expression of PD-1 acts as a sensor to rapidly tune the pool of eTreg cells at homeostasis and during inflammatory processes.

Impact of secondary TCR engagement on the heterogeneity of pathogen-specific CD8+ T cell response during acute and chronic toxoplasmosis.

Initial TCR engagement (priming) of naive CD8+ T cells results in T cell expansion, and these early events influence the generation of diverse effector and memory populations. During infection, activated T cells can re-encounter cognate antigen, but how these events influence local effector responses or formation of memory populations is unclear. To address this issue, OT-I T cells which express the Nur77-GFP reporter of TCR activation were paired with the parasite Toxoplasma gondii that expresses OVA to assess how secondary encounter with antigen influences CD8+ T cell responses. During acute infection, TCR stimulation in affected tissues correlated with parasite burden and was associated with markers of effector cells while Nur77-GFP- OT-I showed signs of effector memory potential. However, both Nur77-GFP- and Nur77-GFP+ OT-I from acutely infected mice formed similar memory populations when transferred into naive mice. During the chronic stage of infection in the CNS, TCR activation was associated with large scale transcriptional changes and the acquisition of an effector T cell phenotype as well as the generation of a population of CD103+ CD69+ Trm like cells. While inhibition of parasite replication resulted in reduced effector responses it did not alter the Trm population. These data sets highlight that recent TCR activation contributes to the phenotypic heterogeneity of the CD8+ T cell response but suggest that this process has a limited impact on memory populations at acute and chronic stages of infection.

Implementation of Enhanced Recovery Protocols for Gastrointestinal Surgery in Children: Practical Tools From Key Stakeholders.

INTRODUCTION: We explored patient, caregiver, and provider recommendations for development of a tool kit to implement enhanced recovery protocols (ERPs) for pediatric patients undergoing gastrointestinal surgery. ERPs are widely used for adults to decrease hospital length of stay, hospital costs, and complications while hastening patient recovery after surgery. With limited data available for ERPs among pediatric populations informed modification of adult ERPs is needed to facilitate successful implementation for pediatric surgery. METHODS: Using a qualitative research design, semistructured interviews were conducted with hospital-based teams including surgeons, anesthesiologists, gastroenterologists, nursing, and physician assistants. Four in-person focus groups were held at two pediatric hospitals with patients and caregivers. Codes were developed and applied to interview and focus groups transcripts for structural content analysis. Thematic analysis guided by the Active Implementation Framework, included recommendations that informed ERP implementation tool kit development. RESULTS: Key components of the ERP tool kit included the need for a structured and systematic approach, leadership support from key champions, and buy-in from surgical partners and hospital management. Providers identified the need for multimodal educational materials on ERP elements for staff and patients; use of uniform checklists, care sets and an electronic repository to collect outcome data for quality assurance assessment. Patients and caregivers endorsed expansion of the team to include child-life specialists, nutritionists, and patient-parent supporters to help navigate the surgical experience. CONCLUSIONS: This study is the first to leverage key input from patients, caregivers, and providers to identify practical components for an ERP implementation tool kit for children undergoing gastrointestinal surgery.

Age- and Sex-Specific Needs for Children Undergoing Inflammatory Bowel Disease Surgery: A Qualitative Study.

INTRODUCTION: The use of enhanced recovery protocols (ERP) is extending to pediatric surgical populations, such as patients with inflammatory bowel diseases (IBDs). Given the variation in age- and sex-specific characteristics of pediatric IBD patients, it is important to understand the unique needs of subgroups, such as male versus female or preadolescent versus older patients, when implementing ERPs. We gathered clinician, patient, and caregiver perspectives on age- and sex-specific needs for children undergoing IBD surgery. METHODS: We used semistructured interviews and focus groups to assess ERP needs and perceived differences in needs between preadolescent (10-13 y), older (14-19 y), male, and female IBD patients. Participants included clinicians, patients who had recent IBD surgery, and patients' caregivers. RESULTS: Forty-eight clinicians, six patients, and eight caregivers participated. Three broad categories of themes emerged: concerns, needs, and experiences related to the (1) surgical care process; (2) continuum of IBD care; and (3) suggestions to make surgical care more patient centered. With regard to surgical care processes, stakeholders reported different communication needs for preadolescent and older children. Key themes about the continuum of IBD care were the need (1) for support from child life specialists and (b) to address young women's health issues. Suggestions to make surgical care more patient centered included providing older children with patient experiences that reflect their perspective as young adults. CONCLUSIONS: The findings highlight the need to adopt a patient-centered approach for ERP use that actively addresses age- and sex-specific factors while engaging patients and caregivers as partners with clinicians to improve surgical care for children with IBD.

Impact of Ion-Pairing Effects on Linear and Nonlinear Photophysical Properties of Polymethine Dyes*.

The two-photon absorption (2PA) and photophysics of heptamethine dyes featuring cyanine or dipolar electronic structures have been compared for the first time. The perfectly delocalized cyanine system is classically characterized by a two-photon transition matching the vibronic component of its lower energy absorption band. The dipolar species is generated by ion-pairing with a hard counterion in a non-dissociating solvent and displays significant modifications oft he optical properties, including a significant hypochromic shift of absorption, weaker emission and 2PA matching the lower energy transition, thus revealing symmetry breaking within the polymethine electronic structure.

Highly Conjugated, Fused-Ring, Quadrupolar Organic Chromophores with Large Two-Photon Absorption Cross-Sections in the Near-Infrared.

The two-photon absorption (2PA) properties are investigated for two series of organic, π-conjugated, fused-ring, quadrupolar A-π-D-π-A chromophores of the type originally developed as nonfullerene acceptors for organic photovoltaics. These molecules are found to exhibit large nondegenerate two-photon absorption (ND2PA) cross-sections (ca. 6-27 × 103 GM) in the near-infrared (NIR). In the first series, involving molecules of varying core size, ND2PA spectra and cross-sections characterized by femtosecond ND2PA spectroscopy in chloroform solutions reveal that increases in core size, and thus conjugation length, leads to substantially red-shifted and enhanced 2PA. In a second series, variation of the strength of the terminal acceptor (A) with constant core size (seven rings, indacene-based) led to less dramatic variation in the 2PA properties. Among the two core types studied, compounds in which the donor has a thieno[3,2-b]thiophene center demonstrate larger 2PA cross-sections than their indacene-centered counterparts, due to the greater electron-richness of their cores amplifying intramolecular charge transfer. Excited-state absorption (ESA) contributions to nonlinear absorption measured by open-aperture Z-scans are deduced for some of the compounds by analyzing the spectral overlap between 2PA bands and NIR ESA transitions obtained by ND2PA and transient absorption measurements, respectively. ESA cross-sections extracted from transient absorption and irradiance-dependent open-aperture Z-scans are in reasonable agreement, and their moderate magnitudes (ca. 10-21 m2) suggest that, although ESA contributions are non-negligible, the effective response is predominantly instantaneous 2PA.

Nonlinear refraction and absorption measurements of thin films by the dual-arm Z-scan method.

We extend the recently developed dual-arm Z-scan to increase the signal-to-noise ratio (SNR) for measuring the nonlinear refraction (NLR) of thin films on thick substrates. Similar to the case of solutes in solution, the phase shift due to NLR in a thin film can often be dominated by the phase shift due to NLR in the much thicker substrate. SNR enhancement is accomplished by simultaneously scanning a bare substrate and the film plus substrate in two separate but identical Z-scan arms. The subtraction of these signals taken simultaneously effectively cancels the nonlinear signal from the substrate, leaving only the signal from the film. More importantly, the SNR is increased since the correlated noise from effects such as beam-pointing instabilities cancels. To show the versatility of the dual-arm Z-scan method, we perform measurements on semiconductor and organic thin films, some less than 100 nm thick and with thicknesses up to 4 orders of magnitude less than the substrate.

Individually Dispersed Gold Nanoshell-Bearing Cellulose Nanocrystals with Tailorable Plasmon Resonance.

Cellulose nanocrystals (CNCs) can be attractive templates for the generation of functional inorganic/organic nanoparticles, given their fine sizes, aspect ratios, and sustainable worldwide availability in abundant quantities. Here, we present for the first time a scalable, surfactant-free, tailorable wet chemical process for converting commercially available CNCs into individual aspected gold nanoshell-bearing particles with tunable surface plasmon resonance bands. Using a rational cellulose functionalization approach, stable suspensions of positively charged CNCs have been generated. Continuous, conductive, nanocrystalline gold coatings were then applied to the individual, electrostatically stabilized CNCs via decoration with 1-3 nm diameter gold particles followed by electroless gold deposition. Optical analyses indicated that these core-shell nanoparticles exhibited two surface plasmon absorbance bands, with one located in the visible range (near 550 nm) and the other at near infrared (NIR) wavelengths. The NIR band possessed a peak maximum wavelength that could be tuned over a wide range (1000-1300 nm) by adjusting the gold coating thickness. The bandwidth and wavelength of the peak maximum of the NIR band were also sensitive to the particle size distribution and could be further refined by fractionation using viscosity gradient centrifugation.

Calcium Uncaging with Visible Light.

We have designed a nitroaromatic photochemical protecting group that absorbs visible light in the violet-blue range. The chromophore is a dinitro derivative of bisstyrylthiophene (or BIST) that absorbs light very effectively (ε440 = 66,000 M(-1) cm(-1) and two-photon cross section of 350 GM at 775 nm). We developed a "caged calcium" molecule by conjugation of BIST to a Ca(2+) chelator that upon laser flash photolysis rapidly releases Ca(2+) in <0.2 ms. Using the patch-clamp method the optical probe, loaded with Ca(2+), was delivered into acutely isolated mouse cardiac myocytes, where either one- and two-photon uncaging of Ca(2+) induced highly local or cell-wide physiological Ca(2+) signaling events.

Facile Incorporation of Pd(PPh3)2Hal Substituents into Polymethines, Merocyanines, and Perylene Diimides as a Means of Suppressing Intermolecular Interactions.

Compounds with polarizable π systems that are susceptible to attack with nucleophiles at C-Hal (Hal = Cl, Br) bonds react with Pd(PPh3)4 to yield net oxidative addition. X-ray structures show that the resulting Pd(PPh3)2Hal groups greatly reduce intermolecular π-π interactions. The Pd-functionalized dyes generally exhibit solution-like absorption spectra in films, whereas their Hal analogues exhibit features attributable to aggregation.

Luminescent Quadrupolar Borazine Oligomers: Synthesis, Photophysics, and Two-Photon Absorption Properties.

A set of monodisperse bent donor-acceptor-donor-type conjugated borazine oligomers, BnNn+1 (n=1-4), incorporating electron-rich triarylamine donor and electron-deficient triarylborane acceptor units has been prepared through an iterative synthetic approach that takes advantage of highly selective silicon-boron and tin-boron exchange reactions. The effect of chain elongation on the electrochemical, one- and two-photon properties and excited-state photodynamics has been investigated. Strong intramolecular charge transfer (ICT) from the arylamine donors to boryl-centered acceptor sites results in emissions with high quantum yields (Φfl >0.5) in the range of 400-500 nm. Solvatochromic effects lead to solvent shifts as large as ∼70 nm for the shortest member (n=1) and gradually decrease with chain elongation. The oligomers exhibit strong two-photon absorption (2PA) in the visible spectral region with 2PA cross sections as large as 1410 GM (n=4), and broadband excited-state absorption (ESA) attributed to long-lived singlet-singlet and radical cation/anion absorption. The excited-state dynamics also show sensitivity to the solvent environment. Electrochemical observations and DFT calculations (B3LYP/6-31G*) reveal spatially separated HOMO and LUMO levels resulting in highly fluorescent oligomers with strong ICT character. The BnNn+1 oligomers have been used to demonstrate the detection of cyanide anions with association constants of log K>7.

Three-dimensional organic microlasers with low lasing thresholds fabricated by multiphoton and UV lithography.

Cuboid-shaped organic microcavities containing a pyrromethene laser dye and supported upon a photonic crystal have been investigated as an approach to reducing the lasing threshold of the cavities. Multiphoton lithography facilitated fabrication of the cuboid cavities directly on the substrate or on the decoupling structure, while similar structures were fabricated on the substrate by UV lithography for comparison. Significant reduction of the lasing threshold by a factor of ~30 has been observed for cavities supported by the photonic crystal relative to those fabricated on the substrate. The lasing mode spectra of the cuboid microresonators provide strong evidence showing that the lasing modes are localized in the horizontal plane, with the shape of an inscribed diamond.

Nonlinear optical pulse suppression via ultrafast photoinduced electron transfer in an aggregated perylene diimide/oligothiophene molecular triad.

A donor-acceptor-donor triad material in which two quinquethiophene moieties are attached via nonconjugated, flexible bridges to the 1,7-positions (80% isomer) and 1,6-positions (20% isomer) of a perylene diimide (PDI-5T) has been synthesized, and its nonlinear suppression of nanosecond laser pulses in the 680-750 nm range has been studied. The kinetics of the photoinduced charge separation processes have been characterized using femtosecond transient pump-probe spectroscopy. Excitation of either the quinquethiophene donor or perylene diimide acceptor leads to ultrafast (<700 fs) photoinduced charge separation, yielding quinquethiophene and perylene diimide radical ions that are strongly absorbing in the red-near-IR region. Despite the short lifetime (52 ps) of the charge-separated state, reasonably strong nonlinear suppression of nanosecond pulses, with figures-of-merit up to 14, has been realized with 4 mM solutions of PDI-5T. Although the radical ion absorption (RIA) is much stronger at 750 nm than that at 680 or 700 nm, the best optical suppression figures-of-merit were observed at 680 and 700 nm. Comparison of the optical parameters at these wavelengths suggests that the stronger ground-state absorption, due to aggregates of PDI-5T, is responsible for the enhanced figure-of-merit at the shorter wavelength.

Cyanine-like dyes with large bond-length alternation.

Herein, the synthesis and properties of alkyne-bridged carbocations, which are analogous in structure to cyanine dyes, are reported. An alkene-bridged dye, linked at the third position of the indole, was also synthesized as a reference compound. These new carbocations are stable under ambient conditions, allowing characterization by UV/Vis and NMR ((1)H and (13)C) spectroscopies. These techniques revealed a large degree of delocalization of the positive charge, similar to a previously reported porphyrin carbocation. The linear and nonlinear optical properties are compared with cyanine dyes and triarylmethyl cations, to investigate the effects of the bond-length alternation and the overall molecular geometry. The value of Re(γ), the real part of the third-order microscopic polarizability, of -1.3×10(-33)  esu for the alkyne-linked cation is comparable to that of a cyanine dye of similar length. Nondegenerate two-photon absorption spectra showed that the alkene-bridged dye exhibited characteristics of cyanines, whereas the alkyne-bridged dye is reminiscent of octupolar chromophores, such as the triarylmethyl carbocation brilliant green. Such attributes were confirmed and rationalized by quantum chemical calculations.

Linear and nonlinear optical properties of Ag/Au bilayer thin films.

The linear and nonlinear optical properties of Ag/Au bilayer metallic thin films with a total thickness of around 20 nm and with different Ag/Au mass-thickness ratios were studied. This study shows that the spectral dispersion of the effective refractive index of bilayer films can be tuned by controlling the mass-thickness ratio between Au and Ag. Improvement of the figure-of-merit for potential plasmonic applications and linear optical filters in the visible spectral range are reported and discussed. The nonlinear optical properties of bilayer metal films studied using femtosecond white-light continuum pump-probe experiments are also shown to be tunable with this ratio. The nonlinear change of optical path length is extracted from the pump-probe data and agrees with simulated values derived from a combination of the two-temperature model, describing the ultrafast electron heating dynamics, and a physical model that describes the dielectric permittivity of Au as a function of electron and lattice temperature.

Excited state absorption: a key phenomenon for the improvement of biphotonic based optical limiting at telecommunication wavelengths.

Spectroscopic properties, two-photon absorption (TPA) and excited state absorption (ESA), of two organic cyanine dyes and of a ruthenium based organometallic cyanine are compared in order to rationalize their similar ns-optical power limiting (OPL) efficiency in the telecommunication wavelength range. The TPA contribution to the ns-OPL behavior is higher for both organic cyanines, while the main process is a TPA-induced ESA in the case of the organometallic system, in which the ruthenium induces a broadening of the NIR-ESA band and resulting in a strong spectral overlap between TPA and ESA spectra.

Effect of alicyclic ring size on the photophysical and photochemical properties of bis(arylidene)cycloalkanone compounds.

A series of bis(arylidene)cycloalkanone compounds based on cyclobutanone, cyclopentanone, cyclohexanone and cycloheptanone, C4-C7, respectively, with a D-π-A-π-D structure containing the same donor and acceptor but different alicyclic rings was prepared. The effects of alicyclic ring size on the photophysical, photochemical and electrochemical properties of these compounds were investigated systematically. We found that an increase of the number of carbons in the central alicyclic ring leads to changes in geometry, which has significant effects on the conjugation, and photophysical and photochemical properties. These effects include decreases in the fluorescence quantum yield, transient lifetimes, peak extinction coefficients, and the singlet oxygen quantum yield with the increase of the ring size. The one-photon absorption spectra, the two-photon absorption (2PA) spectra, and the fluorescence spectra all show a hypsochromic shift with increasing ring size. The results of this study provide guidance for the design of new cycloketone-based D-π-A-π-D 2PA compounds for photopolymerization and photodynamic therapy applications.

Impact of electronic coupling, symmetry, and planarization on one- and two-photon properties of triarylamines with one, two, or three diarylboryl acceptors.

We have performed a study of the one- and two-photon absorption properties of a systematically varied series of triarylamino-compounds with one, two, or three attached diarylborane arms arranged in linear dipolar, bent dipolar, and octupolar geometries. Two-photon fluorescence excitation spectra were measured over a wide spectral range with femtosecond laser pulses. We found that on going from the single-arm to the two- and three-arm systems, the peak in two-photon absorption (2PA) cross-section is suppressed by factors of 3-11 for the lowest excitonic level associated with the electronic coupling of the arms, whereas it is enhanced by factors of 4-8 for the higher excitonic level. These results show that the coupling of arms redistributes the 2PA cross-section between the excitonic levels in a manner that strongly favors the higher-energy excitonic level. The experimental data on one- and two-photon cross-sections, ground- and excited-state transition dipole moments, and permanent dipole moment differences between the ground and the lowest excited states were compared to the results obtained from a simple Frenkel exciton model and from highly correlated quantum-chemical calculations. It has been found that planarization of the structure around the triarylamine moiety leads to a sizable increase in peak 2PA cross-section for the lowest excitonic level of the two-arm system, whereas for the three-arm system, the corresponding peak was weakened and shifted to lower energy. Our studies show the importance of the interarm coupling, number of arms, and structural planarity on both the enhancement and the suppression of two-photon cross-sections in multiarm molecules.

Photoinduced electron transfer and nonlinear absorption in poly(carbazole-alt-2,7-fluorene)s bearing perylene diimides as pendant acceptors.

This paper reports the synthesis, photophysical behavior, and use in nanosecond optical-pulse suppression of a poly(2,7-carbazole-alt-2,7-fluorene) and a poly(3,6-carbazole-alt-2,7-fluorene) in which the carbazole N-positions are linked by an alkyl chain to one of the nitrogen atoms of a perylene-3,4,9,10-tetracarboxylic diimide (PDI) acceptor. It was found that the PDI pendants on the polymer side chain aggregated even in dilute solution, which extended the onset of PDI absorption into the near-infrared (NIR). Transient-absorption spectra of these polymers provide evidence for efficient electron transfer following either donor or acceptor photoexcitation to form long-lived charge-separated species, which exhibit strong absorption in the NIR. The spectral overlap between the transient species and the long-wavelength absorption edge of the aggregated PDI leads to reverse saturable absorption at 680 nm that can be used for optical-pulse suppression. Additionally, at high input energies, two-photon absorption mechanisms may also contribute to the suppression. PDI-grafted polymers exhibit enhanced optical-pulse suppression compared with blends of model materials composed of unfunctionalized poly(carbazole-alt-2,7-fluorene)s and PDI small molecules.