Mutations in DARS2 result in global dysregulation of mRNA metabolism and splicing.

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a rare neurological disorder caused by the mutations in the DARS2 gene, which encodes the mitochondrial aspartyl-tRNA synthetase. The objective of this study was to understand the impact of DARS2 mutations on cell processes through evaluation of LBSL patient stem cell derived cerebral organoids and neurons. We generated human cerebral organoids (hCOs) from induced pluripotent stem cells (iPSCs) of seven LBSL patients and three healthy controls using an unguided protocol. Single cells from 70-day-old hCOs were subjected to SMART-seq2 sequencing and bioinformatic analysis to acquire high-resolution gene and transcript expression datasets. Global gene expression analysis demonstrated dysregulation of a number of genes involved in mRNA metabolism and splicing processes within LBSL hCOs. Importantly, there were distinct and divergent gene expression profiles based on the nature of the DARS2 mutation. At the transcript level, pervasive differential transcript usage and differential spliced exon events that are involved in protein translation and metabolism were identified in LBSL hCOs. Single-cell analysis of DARS2 (exon 3) showed that some LBSL cells exclusively express transcripts lacking exon 3, indicating that not all LBSL cells can benefit from the "leaky" nature common to splice site mutations. At the gene- and transcript-level, we uncovered that dysregulated RNA splicing, protein translation and metabolism may underlie at least some of the pathophysiological mechanisms in LBSL. To confirm hCO findings, iPSC-derived neurons (iNs) were generated by overexpressing Neurogenin 2 using lentiviral vector to study neuronal growth, splicing of DARS2 exon 3 and DARS2 protein expression. Live cell imaging revealed neuronal growth defects of LBSL iNs, which was consistent with the finding of downregulated expression of genes related to neuronal differentiation in LBSL hCOs. DARS2 protein was downregulated in iNs compared to iPSCs, caused by increased exclusion of exon 3. The scope and complexity of our data imply that DARS2 is potentially involved in transcription regulation beyond its canonical role of aminoacylation. Nevertheless, our work highlights transcript-level dysregulation as a critical, and relatively unexplored, mechanism linking genetic data with neurodegenerative disorders.

Fabrication of polydimethylsiloxane/graphene flexible strain sensors by using the scraping and coating method.

Production of flexible strain sensors is complex, time-consuming, and expensive. In this study, a novel fabrication method of polydimethylsiloxane/graphene nanocomposite conductive materials was proposed by using the scraping and coating method for manufacturing sandwich-shape flexible strain sensors. A ZQ-60B tensile testing machine was employed to test the mechanical properties of flexible sensors with 1%, 3%, and 5% graphene content. The results revealed that the stress and strain of the flexible strain sensor exhibited a linear relationship, and the linear correlation coefficients were 0.99706, 0.99819, and 0.99826, respectively. The concentration of graphene was 1%, 3%, and 5%, and the gauge factors (GFs) of the sensor were 24, 6, and 3, respectively. With the increase in the graphene content, the GF decreased gradually. This phenomenon could be attributed to tunneling, which increased the number of conductive pathways with an increase in the graphene content. Furthermore, the sensor exhibited excellent stability after 100 cycles of stretching/scaling. The finger joint bending test revealed that the flexible strain sensor is reproducible and exhibits excellent application prospects in monitoring human movement and health.

Laser ablation for pharmaceutical nanoformulations: Multi-drug nanoencapsulation and theranostics for HIV.

We introduce the use of laser ablation to develop a multi-drug encapsulating theranostic nanoformulation for HIV-1 antiretroviral therapy. Laser ablated nanoformulations of ritonavir, atazanavir, and curcumin, a natural product that has both optical imaging and pharmacologic properties, were produced in an aqueous media containing Pluronic® F127. Cellular uptake was confirmed with the curcumin fluorescence signal localized in the cytoplasm. Formulations produced with F127 had improved water dispersibility, are ultrasmall in size (20-25 nm), exhibit enhanced cellular uptake in microglia, improve blood-brain barrier (BBB) crossing in an in vitro BBB model, and reduce viral p24 by 36 fold compared to formulations made without F127. This work demonstrates that these ultrasmall femtosecond laser-ablated nanoparticles are effective in delivering drugs across the BBB for brain therapy and show promise as an effective method to formulate nanoparticles for brain theranostics, reducing the need for organic solvents during preparation.

Mechanism of stimulated Mie scattering: Light-induced redistribution of self-assembled nanospheres of two-photon absorbing chromophore.

We report the observation of backward stimulated Mie scattering (SMS) due to light-field induced spatial redistribution of self-assembled nanospheres of a two-photon resonant organic chromophore in water, pumped by ∼10-ns laser pulses of ∼816-nm wavelength. The pump-energy threshold for generating backward stimulated scattering in such a system is remarkably lower than that in pure water. The gain of backscattering originates from an induced Bragg grating that reflects partial energy from the pump beam into the backward Mie scattering beam. Based on the experimental fact that the time-delay of the SMS pulse onset depends on both the pump level and the viscosity of the solvent, a physical model of SMS generation is proposed. Our experimental results have shown that the major contribution to the formation of an induced Bragg grating is spatial redistribution of nanoparticles suspended in the liquid. These nanoparticles are driven by a force that is proportional to the intensity gradient of the standing-wave field resulting from interference between the forward pump beam and the backward Mie scattering beam. When the nanoparticle motion is frozen in a gel-like medium, no SMS is observed, which experimentally supports the validity of the proposed physical model.

[A case of Okur-Chung syndrome caused by CSNK2A1 gene variation and review of literature].

Objective: To summarize the clinical features and gene variation characteristics of a child with Okur-Chung syndrome caused by CSNK2A1 gene variation. Methods: The medical records of one patient who was diagnosed with Okur-Chung syndrome in Department of Pediatrics, Xiangya Hospital of Central South University in July 2018 were analyzed. Using "CSNK2A1" gene as the keyword, relevant information about CSNK2A1 gene was searched at CNKI, Wangfang Data, OMIM, PubMed, ClinVar, Decipher (until August 2018). The characteristics of CSNK2A1 gene variation and the clinical phenotype of children with Okur-Chung syndrome were summarized. Results: The boy, 1 year and 8 months old, was sent to hospital at the age of 1 year and 6 months because of delayed growth for more than 1 year. He was susceptible to cough while eating or drinking. He was also suffering from constipation and poor sleep. Physical examination showed that his body weight was 10.2 kg, microcephalus, broad nasal bridge, micrognathia and hypotonia were observed. Whole exome-sequencing test identified a de novo heterozygous variation c.524A>G (p.D175G) in CSNK2A1 gene. This was the first case report of CSNK2A1 gene variation in the mainland of China. So far, a total of 52 cases were reported worldwide (52 single nucleotide variants), including 35 cases in 7 articles, 9 cases in Decipher database and 14 cases in ClinVar database, 6 of which were also reported in PubMed. In previously reported 52 cases, there were 48 missense variants, whereas, splice and frameshift variations were found in 3 cases and 1 case, respectively. Among the variation sites, p.K198R was the most common sites (12 cases), followed by p.R47 (6 cases), p.R80H (4 cases) and p.S51 (4 cases). Among these 52 cases, only 27 cases have been elaborately described in other studies, so the clinical characteristics were summarized in 28 cases eventually (including 27 cases in the articles and this patient), 27 of whom presented severe intellectual disability or global development delay, 1 case with mild language development delay, and 19 had hypotonia; 8 had autism spectrum disorders, 5 had attention deficit hyperactivity disorder, and 9 had sleep problems. 20 had dysmorphic facial features, 10 of them had microcephalus. 16 had failure to thrive or short stature, 12 had gastrointestinal or oromotor problem, 5 had immunological problem, and 4 had skin abnormalities. Conclusions: The main clinical feature of patients with CSNK2A1 gene variations is intellectual disability with multiple systems involved, such as microcephalus, abnormal facial shape and hypotonia. The variation of CSNK2A1 gene is the cause of Okur-Chung syndrome. Missense variation is the main cause, and P. K198R is the hotspot variation.

Nonlinear Photoacoustic Imaging by in situ Multiphoton Upconversion and Energy Transfer.

In recent years, photoacoustic tomography (PAT) is increasingly used in biomedical research, as it allows for direct visualization of optical absorption in deep tissue. In addition to vascular and hemodynamic imaging using endogenous contrasts, PAT is also capable of imaging neural and molecular dynamics with extrinsic contrasts. While near-infrared (NIR)-absorbing contrasts are preferred for deep tissue imaging, compared to visible-light-absorbing contrasts, they are much harder to design and synthesize with good environmental stability. We introduce here a new PAT mode which utilizes nonlinear multiphoton upconversion of NIR light in situ to visible light, thus exciting locally a dye that can generate strong photoacoustic signal. This approach allows to take advantage of a large library of visible-light-absorbing dyes that can enable functional imaging, such as imaging of voltage, oxygen, pH, and ion channel activities. Two types of upconversion materials are utilized in this work: 1) a two-photon absorbing and emitting dye that is efficiently excited by NIR nanosecond laser pulses to enable pulsed laser-based PAT (pulsed-PAT); and 2) rare-earth containing inorganic nanocrystals that absorb continuous-wave (CW) NIR light by sequential multiphoton absorption through real intermediate states to enable intensity-modulated CW laser-based PAT (CW-PAT). Since both cases produce highly localized nonlinear photoacoustic signal, which has very weak scattering in tissue, we can achieve high contrast 3-D volume imaging of deep tissues. In this study, we validated the principle of our approach in different PAT modes and successfully detected enhanced photoacoustic signals from a visible-light-absorbing dye embedded deep in tissue. With vast variety of functionalized organic dyes operating in the visible range, our mode of nonlinear photoacoustic imaging will find great applications in preclinical and clinical researches.

Alleviating Luminescence Concentration Quenching in Upconversion Nanoparticles through Organic Dye Sensitization.

The phenomenon of luminescence concentration quenching exists widely in lanthanide-based luminescent materials, setting a limit on the content of lanthanide emitter that can be used to hold the brightness. Here, we introduce a concept involving energy harvesting by a strong absorber and subsequent energy transfer to a lanthanide that largely alleviates concentration quenching. We apply this concept to Nd3+ emitters, and we show both experimentally and theoretically that the optimal doping concentration of Nd3+ in colloidal NaYF4:Nd upconverting nanoparticles is increased from 2 to 20 mol% when an energy harvestor organic dye (indocyanine green, ICG) is anchored onto the nanoparticle surface, resulting in ∼10 times upconversion brightness. Theoretical analysis indicated that a combination of efficient photon harvesting due to the large absorption cross section of ICG (∼30 000 times higher than that of Nd3+), non-radiative energy transfer (efficiency ∼57%) from ICG to the surface bound Nd3+ ions, and energy migration among the Nd3+ ions was able to activate Nd3+ ions inside the nanoparticle at a rate comparable with that of the pronounced short-range quenching interaction at elevated Nd3+ concentrations. This resulted in the optimal concentration increase to produce significantly enhanced brightness. Theoretical modeling shows a good agreement with the experimental observation. This strategy can be utilized for a wide range of other lanthanide-doped nanomaterials being utilized for bioimaging and solar cell applications.

Twisted Thiophene-Based Chromophores with Enhanced Intramolecular Charge Transfer for Cooperative Amplification of Third-Order Optical Nonlinearity.

Exploiting synergistic cooperation between multiple sources of optical nonlinearity, we report the design, synthesis, and nonlinear optical properties of a series of electron-rich thiophene-containing donor-acceptor chromophores with condensed π-systems and sterically regulated inter-aryl twist angles. These structures couple two key mechanisms underlying optical nonlinearity, namely, (i) intramolecular charge transfer, greatly enhanced by increased electron density and reduced aromaticity at chromophore thiophene rings and (ii) a twisted chromophore geometry, producing a manifold of close-lying excited states and dipole moment changes between ground and excited states that are nearly twice that of untwisted systems. Spectroscopic, electrochemical, and nonlinear Z-scan measurements, combined with quantum chemical calculations, illuminate relationships between molecular structure and mechanisms of enhancement of the nonlinear refractive index. Experiment and calculations together reveal ground-state structures that are strongly responsive to the solvent polarity, leading to substantial negative solvatochromism (Δλ ≈ 10(2) nm) and prevailing zwitterionic/aromatic structures in the solid state and in polar solvents. Ground-to-excited-state energy gaps below 2.0 eV are obtained in condensed π-systems, with lower energy gaps for twisted versus untwisted systems. The real part of the second hyperpolarizability in the twisted structures is much greater than the imaginary part, with the highest twist angle chromophore giving |Re(γ)/Im(γ)| ≈ 100, making such chromophores very promising for all-optical-switching applications.

Cooperative coupling of cyanine and tictoid twisted π-systems to amplify organic chromophore cubic nonlinearities.

We report a new class of hybrid π-electron chromophores with a large, sign-tunable third-order nonlinear optical (NLO) response, achieved via cooperative coupling of cyanine dye bond-length alternation effects with the rich density of states in zwitterionic twisted π-system chromophores. A combined synthetic, linear/nonlinear spectroscopic, and quantum chemical study reveals exceptional third-order response exceeding the sum of the individual chromophore contributions.

Manipulating nanoscale interactions in a polymer nanocomposite for chiral control of linear and nonlinear optical functions.

The design, synthesis, and supramolecular organization of a nanocomposite in which nanoscale excitonic interactions between quantum dots and the chiral polymer dramatically enhance the optical activity is reported. This material is highly suitable for application in the emerging field of chiral photonics.

Nonlinear optical absorption and stimulated Mie scattering in metallic nanoparticle suspensions.

The nonlinear optical properties of four metallic (Au-, Au/Ag-, Ag-, and Pt-) nanoparticle suspensions in toluene have been studied in both femtosecond and nanosecond regimes. Nonlinear transmission measurements in the femtosecond laser regime revealed two-photon absorption (2PA) induced nonlinear attenuation, while in the nanosecond laser regime a stronger nonlinear attenuation is due to both 2PA and 2PA-induced excited-state absorption. In the nanosecond regime, at input pump laser intensities above a certain threshold value, a new type of stimulated (Mie) scattering has been observed. Being essentially different from all other well known molecular (Raman, Brillouin) stimulated scattering effects, the newly observed stimulated Mie scattering from the metallic nanoparticles exhibits the features of no frequency shift and low pump threshold requirement. A physical model of induced Bragg grating initiated by the backward Mie scattering from metallic nanoparticles is proposed to explain the gain mechanism of the observed stimulated scattering effect.

Mini-nutrition assessment, malnutrition, and postoperative complications in elderly Chinese patients with lung cancer.

PURPOSE: To assist healthcare professionals in using the mini nutrition assessment (MNA) and its short-form (MNASF) for early identification of malnourished elderly lung cancer patients, conducting preoperative nutritional support, and improving patients' postoperative prognosis, quality of life, and survival. METHODS: The MNA with revised cut-off points to better suit the Chinese population was conducted on 103 elderly lung cancer Chinese patients aged 60 or above in the Tianjin Cancer Hospital prior to their scheduled surgery. Patient demographic data, anthropometric parameters, biochemical markers, and postoperative complications were collected and analysed. RESULTS: Of the 103 patients studied 12.6% (13/103) were malnourished, 31.1% (32/103) were at risk of malnutrition, and 56.3% (58/103) had adequate nutrition; the average MNA score was 23.6±3.7. Significant positive correlations were found between total MNA score and body mass index (BMI), mid-arm circumference (MAC), calf circumference (CC), and hemoglobin (Hb) (p<0.05), as well as between total MNA-SF score and BMI, MAC, CC, and total MNA score. Significant negative correlations occurred between total MNA-SF score and age (p<0.05). Among postoperative complications, cardiovascular diseases had the highest morbidity rate (23%), followed by respiratory diseases (22%), and cardiovascular and respiratory diseases combined (19%). No significant relationship between nutritional status with types of morbidity (p=0.235) and postoperative complications (p=0.362) was found. CONCLUSION: The MNA scale is an effective tool to preoperatively evaluate the nutritional status of elderly Chinese patients with lung cancer. These patients have poor nutritional status. Further investigations are needed to re-examine the correlation between the MNA results and postoperative complications.

Superior optical limiting, stabilization, and spatio-temporal reshaping of ultrashort laser pulses in an opto-stable intrinsic polymer film.

A chemically modified poly(fluorene-alt-benzothiadiazole) (PFBT) polymer film is reported to exhibit high two-photon absorbing capability and chemical/physical stability upon the action of high-power laser pulses of ~780 nm wavelength and ~160 fs duration. A nonlinear transmission measurement is conducted by varying the input intensity from ~20 to ~600 GW/cm2, the corresponding nonlinear transmission of a ~70 µm thick film is reduced from ~0.8 to 0.18, indicating a superior optical limiting behavior. In the meantime, intensity fluctuation of laser pulses can be significantly reduced after passing through the same film sample. Based on the intensity-dependent nonlinear attenuation mechanism, a straightforward optical reshaping effect on spatio-temporal profiles of the laser pulses has also been demonstrated.

Twisted π-system chromophores for all-optical switching.

Molecular chromophores with twisted π-electron systems have been shown to possess unprecedented values of the quadratic hyperpolarizability, ß, with very large real parts and much smaller imaginary parts. We report here an experimental and theoretical study which shows that these twisted chromophores also possess very large values of the real part of the cubic hyperpolarizability, γ, which is responsible for nonlinear refraction. Thus, for the two-ring twisted chromophore TMC-2 at 775 nm, relatively close to one-photon resonance, n(2) extrapolated to neat substance is large and positive (1.87 × 10(-13) cm(2)/W), leading to self-focusing. Furthermore, the third-order response includes a remarkably low two-photon absorption coefficient, which means minimal nonlinear optical losses: the T factor, α(2)λ/n(2), is 0.308. These characteristics are attributed to closely spaced singlet biradical and zwitterionic states and offer promise for applications in all-optical switching.

Degenerate multi-photon properties of spirofluorene derivatives.

Two- and three-photon absorption properties of the fluorene-based chromophores have been investigated. The two- and three-photon absorption cross-section are found to be increased with the strength of the electron donor groups in the order of N-ethylcarbazoyl (1), triphenylamino (2), and N,N-dibutylanilino (3) groups. This nonlinear absorption enhancement can be interpreted by the increase of intramolecular charge transfer facilitated by strong electron donors and the decreased detuning energy (deltaE). Furthermore, direct laser microfabrication by two-photon photopolymerization with compound 2 as a two-photon sensitizer was carried out. Laser exposure time-dependent lateral voxel size has also been studied.

Additive controlled synthesis of gold nanorods (GNRs) for two-photon luminescence imaging of cancer cells.

Gold nanorods (GNRs) with a longitudinal surface plasmon resonance peak that is tunable from 600 to 1100 nm have been fabricated in a cetyl trimethylammoniumbromide (CTAB) micellar medium using hydrochloric acid and silver nitrate as additives to control their shape and size. By manipulating the concentrations of silver nitrate and hydrochloric acid, the aspect ratio of the GNRs was reliably and reproducibly tuned from 2.5 to 8. The GNRs were first coated with polyelectrolyte multilayers and then bioconjugated to transferrin (Tf) to target pancreatic cancer cells. Two-photon imaging excited from the bioconjugated GNRs demonstrated receptor-mediated uptake of the bioconjugates into Panc-1 cells, overexpressing the transferrin receptor (TfR). The bioconjugated GNR formulation exhibited very low toxicity, suggesting that it is biocompatible and potentially suitable for targeted two-photon bioimaging.

Backward stimulated Bragg scattering in multiphoton active CdTe(x)Se(1-x) quantum dots system.

The backward stimulated Bragg scattering (SBgS) of CdTe(x)Se(1-x) quantum dots in chloroform is investigated at three pump laser wavelengths (532, 816, and 1064 nm) in nanosecond regime. The spectral and temporal structures of the backward stimulated scattering and pump threshold dependence on the concentration are presented in this paper. The energy conversion efficiency from input pump pulse to SBgS pulse was measured to be >or=14%. In addition, the samples exhibit multi- (two-, three-)photon absorption capability over the spectral range we investigated. More importantly, both mechanisms of SBgS and multiphoton absorption provided an enhanced optical limiting performance. The measured nonlinear transmissivity was changed from approximately 0.73 to approximately 0.17 for 532 nm laser pulses and from approximately 0.9 to approximately 0.35 for 816 nm laser pulses when the input pulse energy was changed from 10 to approximately 1500 microJ.

Two- and three-photon absorption and frequency upconverted emission of silicon quantum dots.

In this communication, we present the experimental results of two- and three-photon excitation studies on silicon quantum dots (QDs) in chloroform (as well as in water) by using femtosecond laser pulses with wavelengths of 778 and 1,335 nm and a pulse duration approximately 160 fs. The photoluminescence spectral distributions are nearly the same upon one-, two-, and three-photon excitation. With one- and two-photon excitation, the temporal relaxation measurements of photoluminescence emission manifest the same multiexponential decay behavior in the time range from 0.05 ns to 15 micros, characterized by three successive decay constants: 0.75 ns, 300 ns, and 5 micros, respectively. Finally, the two-photon absorption spectrum in the spectral range of 650-900 nm and the three-photon absorption spectrum in the spectral range of 1,150-1,400 nm have been measured.

Novel fluorophore based on a multi-substituted olefin skeleton with enhanced three-photon absorption in the femtosecond regime.

A new multipolar fluorophore based on a multi-substituted olefin skeleton that possesses strong three-photon absorption and optical-limiting properties in the femtosecond regime has been designed and synthesized; this archetype suggests a new strategy to further optimize molecular structures toward enhanced nonlinear absorptivities based on known materials.