Analysis of leadership and team management skills of middle-level healthcare managers of Valsad district, Gujarat.

Background: The healthcare managers need to develop the managerial skills and use it for better healthcare delivery. A manager requires leadership skill to empower employees and motivate them to work in an efficient manner to achieve organizational goal. Motivating employees/subordinates and developing positive attitude toward them is one of the crucial skills that the leader needs to develop. The way health team works as a unit affects the outcome and needs good leader. With this background, the current study tends to explore the managerial skills of middle-level managers. Objectives: 1. To assess the leadership and team management skills of middle-level managers and 2. To find out motivational factors used by managers. Materials and Methods: A cross-sectional study was conducted among district-level healthcare managers and medical officers. Data collection was performed via semistructured and scale-based questionnaire and analyzed using Microsoft office excel. Results: 60% of managers had participative leadership style. Team work skills were fair enough among the managers. 53% of medical officers were freshly appointed with experience of less than one year. The middle-level managers used appreciation of work (41.8%) as major motivator of the team. Conclusions: The middle-level healthcare managers have good leadership quality as well as teamwork skills. Appreciation of work is commonly used motivator.

Structural analysis of platelet fragments and extracellular vesicles produced by apheresis platelets during storage.

ABSTRACT: Platelets (PLTs) for transfusion can be stored for up to 7 days at room temperature (RT). The quality of apheresis PLTs decreases over storage time, which affects PLT hemostatic functions. Here, we characterized the membranous particles produced by PLT storage lesion (PSLPs), including degranulated PLTs, PLT ghosts, membrane fragments, and extracellular membrane vesicles (PEVs). The PSLPs generated in apheresis platelet units were analyzed on days 1, 3, 5, and 7 of RT storage. A differential centrifugation and a sucrose density gradient were used to separate PSLP populations. PSLPs were characterized using scanning and transmission electron microscopy (EM), flow cytometry (FC), and nanoparticle tracking analysis (NTA). PSLPs have different morphologies and a broad size distribution; FC and NTA showed that the concentration of small and large PSLPs increases with storage time. The density gradient separated 3 PSLP populations: (1) degranulated PLTs, PLT ghosts, and large PLT fragments; (2) PEVs originated from PLT activation and organelles released by necrotic PLTs; and (3) PEV ghosts. Most PSLPs expressed phosphatidyl serine and induced thrombin generation in the plasma. PSLPs contained extracellular mitochondria and some had the autophagosome marker LC3. PSLPs encompass degranulated PLTs, PLT ghosts, large PLT fragments, large and dense PEVs, and low-density PEV ghosts. The activation-related PSLPs are released, particularly during early stage of storage (days 1-3), and the release of apoptosis- and necrosis-related PSLPs prevails after that. No elevation of LC3- and TOM20-positive PSLPs indicates that the increase of extracellular mitochondria during later-stage storage is not associated with PLT mitophagy.

Effect of Temperature on Thrombogenicity Testing of Biomaterials in an In Vitro Dynamic Flow Loop System.

To develop and standardize a reliable in vitro dynamic thrombogenicity test protocol, the key test parameters that could impact thrombus formation need to be investigated and understood. In this study, we evaluated the effect of temperature on the thrombogenic responses (thrombus surface coverage, thrombus weight, and platelet count reduction) of various materials using an in vitro blood flow loop test system. Whole blood from live sheep and cow donors was used to assess four materials with varying thrombogenic potentials: negative-control polytetrafluoroethylene (PTFE), positive-control latex, silicone, and high-density polyethylene (HDPE). Blood, heparinized to a donor-specific concentration, was recirculated through a polyvinyl chloride tubing loop containing the test material at room temperature (22-24°C) for 1 hour, or at 37°C for 1 or 2 hours. The flow loop system could effectively differentiate a thrombogenic material (latex) from the other materials for both test temperatures and blood species ( p < 0.05). However, compared with 37°C, testing at room temperature appeared to have slightly better sensitivity in differentiating silicone (intermediate thrombogenic potential) from the relatively thromboresistant materials (PTFE and HDPE, p < 0.05). These data suggest that testing at room temperature may be a viable option for dynamic thrombogenicity assessment of biomaterials and medical devices.

Comparison of animal and human blood for in vitro dynamic thrombogenicity testing of biomaterials.

BACKGROUND: To determine suitable alternatives to human blood for in vitro dynamic thrombogenicity testing of biomaterials, four different animal blood sources (ovine, bovine, and porcine blood from live donors, and abattoir porcine blood) were compared to fresh human blood. METHODS: To account for blood coagulability differences between individual donors and species, each blood pool was heparinized to a donor-specific concentration immediately before testing in a dynamic flow loop system. The target heparin level was established using a static thrombosis pre-test. For dynamic testing, whole blood was recirculated at room temperature for 1 h at 200 ml/min through a flow loop containing a single test material. Four materials with varying thrombotic potentials were investigated: latex (positive control), polytetrafluoroethylene (PTFE) (negative control), silicone (intermediate thrombotic potential), and high-density polyethylene (HDPE) (historically thromboresistant). Thrombus weight and surface area coverage on the test materials were quantified, along with platelet count reduction in the blood. RESULTS: While donor-specific heparin levels varied substantially from 0.6 U/ml to 7.0 U/ml among the different blood sources, each source was able to differentiate between the thrombogenic latex and the thromboresistant PTFE and HDPE materials (p < 0.05). However, only donor ovine and bovine blood were sensitive enough to differentiate an increased response for the intermediate thrombotic silicone material compared to PTFE and HDPE. CONCLUSIONS: These results demonstrated that multiple animal blood sources (particularly donor ovine and bovine blood) may be suitable alternatives to fresh human blood for dynamic thrombogenicity testing when appropriate control materials and donor-specific anticoagulation levels are used.

Characterization of Complex Drug Formulations Using Cryogenic Scanning Electron Microscopy (Cryo-SEM).

The physicochemical properties of complex drug formulations, including liposomes, suspensions, and emulsions, are important for understanding drug release mechanisms, quality control, and regulatory assessment. It is ideal to characterize these complex drug formulations in their native hydrated state. This article describes the characterization of complex drug formulations in a frozen-hydrated state using cryogenic scanning electron microscopy (cryo-SEM). In comparison to other techniques, such as optical microscopy or room-temperature scanning electron microscopy, cryo-SEM combines the advantage of studying hydrated samples with high-resolution imaging capability. Detailed information regarding cryo-fixation, cryo-fracture, freeze-etching, sputter-coating, and cryo-SEM imaging is included in this article. A multivesicular liposomal complex drug formulation is used to illustrate the impact of different cryogenic sample preparation conditions. In addition to drug formulations, this approach can also be applied to biological samples (e.g., cells, bacteria) and soft-matter samples (e.g., hydrogels). © Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Basic Protocol 1: Cryo-fixation to preserve the native structure of samples using planchettes Alternate Protocol: Cryo-fixation to preserve the native structure of biological samples on sapphire disks Basic Protocol 2: Sample preparation for cross-sectional cryo-SEM imaging Basic Protocol 3: Cryo-SEM imaging and microanalysis.

Analyzing ophthalmic suspension particle size distributions using laser diffraction: Placebo background subtraction method.

The current study demonstrated that the presence of excipients can interfere with the measurement of particle size distribution (PSD), a critical quality attribute of ophthalmic suspensions, by laser diffraction (LD) and that a placebo background subtraction approach can eliminate the impact of excipients on the PSD measurement. Commercially available loteprednol etabonate and brinzolamide ophthalmic suspensions were used as model suspensions. The impact of excipients in these formulations on the LD measurements was determined using a one-factor-at-a-time experimental design approach, using National Institute of Standards and Technology (NIST) traceable polystyrene particle size standards as references. Among the evaluated excipients, polymers containing polyacrylic acid were found to interfere with the PSD analysis by creating the LD signals correspond to particles ranging from a few micrometers to a hundred micrometers in size. As a result, the measured PSD of active pharmaceutical ingredient (API) particles in the formulation overlapped with or superimposed on the excipient PSD signal, leading to erroneous interpretation of the API particle size. Additionally, dispersion of brinzolamide particles in unsaturated solutions led to rapid dissolution of brinzolamide particles during the measurement, resulting in underestimation of the particle size range. Here, a placebo background subtraction approach was developed to eliminate the interference of the excipients. This newly developed LD method was also evaluated using orthogonal methods, including polarized light microscopy and scanning electron microscopy (SEM). The strategy used in this study to eliminate the interference of excipients may also be useful for other heterogeneous dispersions where excipient interference may be of concern.

In vitro physicochemical characterization and dissolution of brinzolamide ophthalmic suspensions with similar composition.

The quality of an ophthalmic suspension is crucial for its in vivo performance, and often impact product's effectiveness. An in-depth understanding of critical quality attributes (CQAs) of ophthalmic suspensions such as particle size distribution (PSD) and rheology, as well as the impact of these CQAs on product performance are important for successful product development, quality control, and regulatory approval. This study employed brinzolamide ophthalmic suspension, 1%, as a model ophthalmic product, and six batches were manufactured using an innovative planetary centrifugal milling (PCM) process. Three batches were manufactured to have distinctly different PSD. These three batches had qualitatively (Q1) and quantitatively (Q2) the same composition as the model drug product (i.e., Azopt), while the differences in PSD were introduced by changing only the manufacturing process parameters. On the other hand, changes in rheology were introduced by altering the input level of the viscosity enhancing polymer in the formulation. A systematic approach was employed to understand the relation between manufacturing process parameters, CQAs, and in vitro product performance. Among the evaluated CQAs, PSD, rheology, surface tension, and drug dissolution were found more sensitive to the changes in the manufacturing processes. Most notably, we developed a rapid dissolution method (completed within minutes) employing in-situ fiber optic UV dissolution system. This novel dissolution method mimics the environmental conditions of the eye such as dissolution under "non-sink" condition and under high shear (from blinking). The method was highly discriminatory to differences in the PSD in the suspension. This study also revealed an important relation between the PSD of the suspension and its rheology which originated as a result of an interaction at the molecular level between the solid drug particles and the viscosity enhancing polymers. These findings underscore the need to evaluate CQAs of the ophthalmic suspensions in concert rather than separately when comparing ophthalmic drug products and product performance.

Crossover between anti- and pro-oxidant activities of different manganese oxide nanoparticles and their biological implications.

Manganese oxide nanoparticles (MnOx NPs) have been suggested to possess several enzyme-like activities. However, studies often used either color change or fluorescence to determine the catalytic activity. Despite the simplicity and sensitivity of these probes, these methods may give distracting artifacts or not reflect the catalytic activities in biological systems. To address this issue, herein, we used electron spin resonance (ESR) spectroscopy, a technique proven effective in identifying and quantifying the free radicals produced/scavenged in nanomaterial-catalyzed reactions, to systematically evaluate the catalytic activities of three MnOx NPs (MnO2, Mn2O3, and Mn3O4 NPs) towards biologically relevant antioxidants (ascorbate and glutathione (GSH)) and reactive oxygen species (ROS) (hydrogen peroxide (H2O2), superoxide anion, and hydroxyl radical). We found that all three MnOx NPs possess both pro- and anti-oxidant activities, including oxidase-, catalase-, and superoxide dismutase (SOD)-like activities but without peroxidase-like or hydroxyl radical scavenging activity. In addition, there are differences among these MnOx NPs in their catalytic activities towards different reactions. Mn2O3 shows the strongest ascorbate oxidation activity, followed by MnO2 and Mn3O4, while Mn3O4 shows the strongest oxidation efficiency towards GSH compared to Mn2O3 and MnO2. In the catalyzed decomposition of H2O2, MnO2 NPs show higher efficiency in the generation of molecular oxygen than Mn2O3 or Mn3O4. Cellular studies indicate that all three MnOx NPs induced concentration-dependent decreases in the cell viability, with Mn3O4 > Mn3O2 > MnO2. At lower concentrations (<100 µM), consistent with the enzyme-like activities detected in solution, all three NPs significantly decreased H2O2-induced cytotoxicity in Caco-2 cells. Our study determined the multi-enzymatic activities of MnOx NPs and exhibited differences among MnOx NPs of different valences in their enzyme-like activities and their biological implications; these results provide valuable information for safe and efficient applications of MnOx NPs as ROS-scavenging biomedical nanomaterials.

Detection and Sizing of Submicron Particles in Biologics With Interferometric Scattering Microscopy.

We demonstrate the application of interferometric scattering microscopy (IFS) for characterizing submicron particles in stir-stressed monoclonal antibody. IFS uses a layered silicon sensor and modified optical microscope to rapidly visualize and determine the particle size distribution (PSD) of submicron particles based on their scattering intensity, which is directly proportional to particle mass. Limits for particle size and optimal solution concentration were established for IFS characterization of submicron particles. We critically compare IFS data with dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) and find IFS is superior to NTA and DLS for determining the realistic shape of the number-based PSD, whereas NTA and DLS provide superior information about absolute particle size. Together, IFS, NTA, and DLS provide complementary information on submicron particles and enable quantitative characterization of the PSD of submicron aggregates. Finally, we explore quantifying particle size with IFS by developing a calibration curve for particle scattering intensity based on correlative scanning electron microscopy imaging. We found that only a subset of isotropic-shaped particles followed the expected proportionality between IFS intensity and particle mass. Overall, this study demonstrates IFS is a simple approach for detecting and quantifying submicron aggregate PSD in protein-based therapeutics.

Graphene oxide catalyzed ketone α-alkylation with alkenes: enhancement of graphene oxide activity by hydrogen bonding.

Direct α-alkylation of carbonyl compounds represents a fundamental bond forming transformation in organic synthesis. We report the first ketone-alkylation using olefins and alcohols as simple alkylating agents catalyzed by graphene oxide. Extensive studies of the graphene surface suggest a pathway involving dual activation of both coupling partners. Notably, we show that polar functional groups have a stabilizing effect on the GO surface, which results in a net enhancement of the catalytic activity. The method represents the first alkylation of carbonyl compounds using graphenes, which opens the door for the development of an array of protocols for ketone functionalization employing common carbonyl building blocks and readily available graphenes.

Cell membrane disintegration and extracellular vesicle release in a model of different size and charge PAMAM dendrimers effects on cultured endothelial cells.

Different nanomaterials are under development for various biomedical applications in which nanoparticles contact blood and vasculature. Therefore, investigating the interactions between nanomaterials and vascular endothelial cells (ECs) is of great importance. Here, we show the effects of polyamidoamine (PAMAM) dendrimers of two different sizes, generation 2 (G2; approximately 3 nm diameter) and generation 7 (G7; 9 nm), with neutral (OH-terminated), anionic (COOH-terminated), and cationic (NH2-terminated) surface modifications on cultured human umbilical vein ECs (HUVECs). We found that only cationic dendrimers (5-100 µg/mL G7-NH2 and 100 µg/mL G2-NH2) and not anionic or neutral dendrimers were cytotoxic to HUVECs. In addition, cationic dendrimers at low concentrations (5 µg/mL) markedly increased the HUVEC surface expression of the proinflammatory activation marker ICAM-1 and phosphatidylserine (PS). Both G2-NH2 and G7-NH2 dendrimers caused g1 arrest, but only G7-NH2 dendrimers induced significant HUVEC apoptosis. G7-NH2 interacted strongly with HUVEC plasma membranes and mitochondrial membranes, and phospholipid vesicles containing G7-NH2 formed, which resulted in extensive plasma membrane blebbing and disintegration. Furthermore, flow cytometric analysis showed that G7-NH2-treated HUVECs released large numbers of extracellular vesicles (EVs) positive for CD105 and PS. A notable population of EVs positive for the mitochondrial marker TOM20 but negative for the autophagosome marker LC3 was found. In summary, large cationic PAMAM dendrimers (G7-NH2) showed both proinflammatory and proapoptotic effects in ECs; at high dendrimer concentrations, these effects were accompanied by necrotic cytotoxicity. G7-NH2 caused plasma and mitochondrial membrane disintegration and the release of EVs, including EVs of mitochondrial origin that were not associated with mitophagy.

Dissecting the biochemical architecture and morphological release pathways of the human platelet extracellular vesiculome.

Platelet extracellular vesicles (PEVs) have emerged as potential mediators in intercellular communication. PEVs exhibit several activities with pathophysiological importance and may serve as diagnostic biomarkers. Here, imaging and analytical techniques were employed to unveil morphological pathways of the release, structure, composition, and surface properties of PEVs derived from human platelets (PLTs) activated with the thrombin receptor activating peptide (TRAP). Based on extensive electron microscopy analysis, we propose four morphological pathways for PEVs release from TRAP-activated PLTs: (1) plasma membrane budding, (2) extrusion of multivesicular α-granules and cytoplasmic vacuoles, (3) plasma membrane blistering and (4) "pearling" of PLT pseudopodia. The PLT extracellular vesiculome encompasses ectosomes, exosomes, free mitochondria, mitochondria-containing vesicles, "podiasomes" and PLT "ghosts". Interestingly, a flow cytometry showed a population of TOM20+LC3+ PEVs, likely products of platelet mitophagy. We found that lipidomic and proteomic profiles were different between the small PEV (S-PEVs; mean diameter 103 nm) and the large vesicle (L-PEVs; mean diameter 350 nm) fractions separated by differential centrifugation. In addition, the majority of PEVs released by activated PLTs was composed of S-PEVs which have markedly higher thrombin generation activity per unit of PEV surface area compared to L-PEVs, and contribute approximately 60% of the PLT vesiculome procoagulant potency.

Isolation, analytical measurements, and cell line studies of the iron-bryostatin-1 complex.

Bryostatin-1 is a marine natural product that has demonstrated medicinal activity in pre-clinical and clinical trials for the treatment of cancer, Alzheimer's disease, effects of stroke, and HIV. In this study, iron-bryostatin-1 was obtained using a pharmaceutical aquaculture technique developed by our lab that cultivates marine bacteria for marine natural product extraction. Analytical measurements (1)H and (13)C NMR, mass spectrometry, and flame atomic absorption were utilized to confirm the presence of an iron-bryostatin-1 complex. The iron-bryostatin-1 complex produced was then tested against the National Cancer Institute's 60 cell line panel. Adding iron to bryostatin-1 lowered the anti-cancer efficacy of the compound.

P-Doped Porous Carbon as Metal Free Catalysts for Selective Aerobic Oxidation with an Unexpected Mechanism.

An extremely simple and rapid (seconds) approach is reported to directly synthesize gram quantities of P-doped graphitic porous carbon materials with controlled P bond configuration. For the first time, it is demonstrated that the P-doped carbon materials can be used as a selective metal free catalyst for aerobic oxidation reactions. The work function of P-doped carbon materials, its connectivity to the P bond configuration, and the correlation with its catalytic efficiency are studied and established. In direct contrast to N-doped graphene, the P-doped carbon materials with higher work function show high activity in catalytic aerobic oxidation. The selectivity trend for the electron donating and withdrawing properties of the functional groups attached to the aromatic ring of benzyl alcohols is also different from other metal free carbon based catalysts. A unique catalytic mechanism is demonstrated, which differs from both GO and N-doped graphene obtained by high temperature nitrification. The unique and unexpected catalytic pathway endows the P-doped materials with not only good catalytic efficiency but also recyclability. This, combined with a rapid, energy saving approach that permits fabrication on a large scale, suggests that the P-doped porous materials are promising materials for "green catalysis" due to their higher theoretical surface area, sustainability, environmental friendliness, and low cost.

π-Plasmon absorption of carbon nanotubes for the selective and sensitive detection of Fe3+ ions.

Inspired by the remarkable electronic and optical properties of single walled carbon nanotubes (SWNTs), various molecular sensing devices with sensitivity down to the single molecule level have been developed. However, most sensing approaches such as field effect transistors or near infrared (NIR) fluorescence require the rigorous debundling and separation of metallic tubes and semiconducting tubes in order to reach the desired high sensitivity. Interestingly, all carbon nanomaterials including carbon nanotubes, graphite, graphene, and even amorphous carbon exhibit extremely strong π-plasmon absorption in the ultraviolet region. This strong absorption has been studied as an undesired optical background for applications based on visible and NIR absorptions. For the first time, we found that the strong π-plasmon absorption of SWNTs in the ultraviolet region is extremely sensitive to ion binding. It is even much more sensitive than the absorption in the visible and NIR regions. Herein, we present our first exploration into using the extremely strong plasmon absorption of SWNTs to develop a new sensing platform for the detection of metallic ions. The detection selectivity is realized by modifying the surface of SWNTs with molecular ligands that have a high specificity for metal ions. As a demonstration, the new method is applied to selectively detect iron ions (Fe3+) by modifying the surface of the SWNTs with deferoxamine (DFO), a natural bacterial siderophore, which has a high specificity and affinity for Fe3+. The selective detection of Fe3+ in both aqueous solution and complex rain water is achieved with a pM level of sensitivity and detection limit. In situ resonant Raman spectroscopy demonstrated that the sensitive detection possibly involves electron transfer between the formed Fe-DFO complexes and the SWNTs. We envisage that it can be used to detect other metal ions when a specific binding chelator is attached to the carbon nanotube surface.

Graphene-Catalyzed Direct Friedel-Crafts Alkylation Reactions: Mechanism, Selectivity, and Synthetic Utility.

Transition-metal-catalyzed alkylation reactions of arenes have become a central transformation in organic synthesis. Herein, we report the first general strategy for alkylation of arenes with styrenes and alcohols catalyzed by carbon-based materials, exploiting the unique property of graphenes to produce valuable diarylalkane products in high yields and excellent regioselectivity. The protocol is characterized by a wide substrate scope and excellent functional group tolerance. Notably, this process constitutes the first general application of graphenes to promote direct C-C bond formation utilizing polar functional groups anchored on the GO surface, thus opening the door for an array of functional group alkylations using benign and readily available graphene materials. Mechanistic studies suggest that the reaction proceeds via a tandem catalysis mechanism in which both of the coupling partners are activated by interaction with the GO surface.

Phthalocyanine-loaded graphene nanoplatform for imaging-guided combinatorial phototherapy.

We report a novel cancer-targeted nanomedicine platform for imaging and prospect for future treatment of unresected ovarian cancer tumors by intraoperative multimodal phototherapy. To develop the required theranostic system, novel low-oxygen graphene nanosheets were chemically modified with polypropylenimine dendrimers loaded with phthalocyanine (Pc) as a photosensitizer. Such a molecular design prevents fluorescence quenching of the Pc by graphene nanosheets, providing the possibility of fluorescence imaging. Furthermore, the developed nanoplatform was conjugated with poly(ethylene glycol), to improve biocompatibility, and with luteinizing hormone-releasing hormone (LHRH) peptide, for tumor-targeted delivery. Notably, a low-power near-infrared (NIR) irradiation of single wavelength was used for both heat generation by the graphene nanosheets (photothermal therapy [PTT]) and for reactive oxygen species (ROS)-production by Pc (photodynamic therapy [PDT]). The combinatorial phototherapy resulted in an enhanced destruction of ovarian cancer cells, with a killing efficacy of 90%-95% at low Pc and low-oxygen graphene dosages, presumably conferring cytotoxicity to the synergistic effects of generated ROS and mild hyperthermia. An animal study confirmed that Pc loaded into the nanoplatform can be employed as a NIR fluorescence agent for imaging-guided drug delivery. Hence, the newly developed Pc-graphene nanoplatform has the significant potential as an effective NIR theranostic probe for imaging and combinatorial phototherapy.

Microwave Enabled One-Pot, One-Step Fabrication and Nitrogen Doping of Holey Graphene Oxide for Catalytic Applications.

The unique properties of a holey graphene sheet, referred to as a graphene sheet with nanoholes in its basal plane, lead to wide range of applications that cannot be achieved by its nonporous counterpart. However, the large-scale solution-based production requires graphene oxide (GO) or reduced GO (rGO) as the starting materials, which take hours to days for fabrication. Here, an unexpected discovery that GO with or without holes can be controllably, directly, and rapidly (tens of seconds) fabricated from graphite powder via a one-step-one-pot microwave assisted reaction with a production yield of 120 wt% of graphite is reported. Furthermore, a fast and low temperature approach is developed for simultaneous nitrogen (N) doping and reduction of GO sheets. The N-doped holey rGO sheets demonstrate remarkable electrocatalytic capabilities for the electrochemical oxygen reduction reaction. The existence of the nanoholes provides a "short cut" for efficient mass transport and dramatically increases edges and surface area, therefore, creates more catalytic centers. The capability of rapid fabrication and N-doping as well as reduction of holey GO can lead to development of an efficient catalyst that can replace previous coin metals for energy generation and storage, such as fuel cells and metal-air batteries.

Differential effect of buffering agents on the crystallization of gemcitabine hydrochloride in frozen solutions.

The purpose of this study was to evaluate the differential effect of buffering agents on the crystallization of gemcitabine hydrochloride (GHCl) in frozen solutions. Four buffering agents, viz. citric acid (CA), malic acid (MA), succinic acid (SA) and tartaric acid (TA) were selected and their effect on GHCl crystallization was monitored using standard DSC and low temperature XRD. Onset of GHCl crystallization during heating run in DSC was measured to compare the differential effect of buffering agents. Glass transition temperature (Tg'), unfrozen water content in the freeze concentrate and crystallization propensity of the buffering agents was also determined for mechanistic understanding of the underlying effects. CA and MA inhibited while SA facilitated crystallization of GHCl even at 25 mM concentration. Increasing the concentration enhanced their effect. However, TA inhibited GHCl crystallization at concentrations <100mM and facilitated it at concentrations ≥100 mM. Lyophilization of GHCl with either SA or TA yielded elegant cakes, while CA and MA caused collapse. Tg' failed to explain the inhibitory effects of CA, MA and TA as all buffering agents lowered the Tg' of the system. Differential effect of buffering agents on GHCl crystallization could be explained by consideration of two opposing factors: (i) their own crystallization tendency and (ii) unfrozen water content in the freeze concentrate. In conclusion, it was established that API crystallization in frozen solution is affected by the type and concentration of the buffering agents.

Direct production of graphene nanosheets for near infrared photoacoustic imaging.

Hummers method is commonly used for the fabrication of graphene oxide (GO) from graphite particles. The oxidation process also leads to the cutting of graphene sheets into small pieces. From a thermodynamic perspective, it seems improbable that the aggressive, somewhat random oxidative cutting process could directly result in graphene nanosheets without destroying the intrinsic π-conjugated structures and the associated exotic properties of graphene. In Hummers method, both KMnO4 and NO2(+) (nitronium ions) in concentrated H2SO4 solutions act as oxidants via different oxidation mechanisms. From both experimental observations and theoretical calculations, it appears that KMnO4 plays a major role in the observed oxidative cutting and unzipping processes. We find that KMnO4 also limits nitronium oxidative etching of graphene basal planes, therefore slowing down graphene fracturing processes for nanosheet fabrication. By intentionally excluding KMnO4 and exploiting pure nitronium ion oxidation, aided by the unique thermal and kinetic effects induced by microwave heating, we find that graphite particles can be converted into graphene nanosheets with their π-conjugated aromatic structures and properties largely retained. Without the need of any postreduction processes to remove the high concentration of oxygenated groups that results from Hummers GO formation, the graphene nanosheets as-fabricated exhibit strong absorption, which is nearly wavelength-independent in the visible and near-infrared (NIR) regions, an optical property typical for intrinsic graphene sheets. For the first time, we demonstrate that strong photoacoustic signals can be generated from these graphene nanosheets with NIR excitation. The photo-to-acoustic conversion is weakly dependent on the wavelength of the NIR excitation, which is different from all other NIR photoacoustic contrast agents previously reported.