1,134 research outputs found
Monitoring prohemostatic treatment in bleeding patients
Acutely bleeding patients are commonly found in the trauma and major surgery scenarios. They require prompt and effective treatment to restore an adequate hemostatic pattern, to avoid serious and sometimes life-threatening complications.Different prohemostatic treatments are available, including allogeneic blood derivatives (fresh frozen plasma, platelet concentrates, and cryoprecipitates), prothrombin complex concentrates, specific coagulation factors (fibrinogen, recombinant factor XIII, recombinant activated factor VII), and drugs (protamine for patients under heparin treatment, desmopressin, antifibrinolytics).For decades, prohemostatic treatment of the acutely bleeding patient was based on empirical strategies and clinical judgment, both in terms of a correct diagnosis of the mechanism(s) leading to bleeding, and of an assessment of the effects of the treatment. This empirical strategy may lead to excessive or unnecessary use of allogeneic blood products, as well as to an incorrect, inefficacious, or even dangerous treatment. Different monitoring devices are nowadays available for guiding the diagnostic and therapeutic decision-making process in an acutely bleeding patient. This review addresses the available tools for monitoring prohemostatic treatment of the bleeding patient, with a specific respect for point-of-care tests (thromboelastography, thromboelastometry, platelet function tests, and heparin monitoring systems) at the light of the existing evidence
Effect of preoperative P2Y12 and thrombin platelet receptor inhibition on bleeding after cardiac surgery
BACKGROUND:
Drugs that act on the platelet P2Y12 receptor are responsible for postoperative bleeding in cardiac surgery. However, protease-activated receptor (PAR) that reacts to thrombin stimulation might still be active in patients treated with P2Y12 inhibitors. Preoperative platelet function testing could possibly guide the timing of surgery. We investigated the association between P2Y12 receptor and PAR inhibition and bleeding after cardiac surgery.
METHODS:
A retrospective cohort study of 361 patients undergoing cardiac surgery and treated with P2Y12 anti-platelet agents was undertaken. All patients received a preoperative multiplate electrode aggregometry testing of platelet P2Y12 receptor activity (ADPtest) and PAR reactivity with thrombin receptor-activating peptide (TRAP) stimulation. ADPtest and TRAPtest data measured before surgery were analysed for association with postoperative bleeding (ml per 12 h) and severe postoperative bleeding.
RESULTS:
Both the ADPtest and the TRAPtest were significantly (P=0.001) associated with postoperative bleeding. A threshold of 22 U for the ADPtest yielded a negative predictive value (NPV) of 94% and a positive predictive value (PPV) of 20%, and a threshold of 75 U for the TRAPtest yielded an NPV of 95% and a PPV of 23%. In the subgroup of patients with ADPtest <22 U, TRAPtest ≥75 U was not associated with severe bleeding (NPV of 100% and PPV of 37%).
CONCLUSIONS:
In patients taking P2Y12 receptor inhibitors, residual platelet reactivity to thrombin stimulation limits the risk of severe postoperative bleeding
Linear Polyamidoamines as Novel Biocompatible Intumescent Flame Retardants for Cotton
Since the middle of the last century, many industrial and academic researchers have devoted a lot of effort to the development of safe and effective flame- retardants (FR). As regards cotton, phosphorylated compounds were the predominant FR for several decades [1] despite many of them had been shown to be bioaccumulative.[1] Recently, biomolecules including proteins have been proposed as FR.[2] Many linear polyamidoamines (PAAs), a family of synthetic polymers with exceptional structural versatility,[3] have high thermal stability coupled with chain structure and side substituents reminding those of proteins.[4] These features suggested that PAAs could act as FR. This presentation reports on the results obtained with a library of eight PAAs applied as coatings on cotton fabrics from aqueous solutions. All tested PAAs warrant remarkable potential as surface-confined intumescent FR. In ignitability tests, six of them exposed to direct flame for 10 s do not burn, but produce carbonaceous crusts sheltering the underneath sample. Thermogravimetric analyses show that at T 65 400 \ub0C all PAAs leave in air substantial char residues that oxidize at T > 500 \ub0C. At 450 \ub0C they form porous carbonaceous structures indicating the tendency to intumesce. In horizontal flame spread tests, cotton stripes impregnated with most PAAs extinguish flame at add-ons ranging from 4 to 20%, whereas untreated cotton vigorously burns without leaving residues. Upon 35 kW/m2 heat flux, all PAA-treated samples significantly reduce the main combustion parameters.
References
[1] R. A. Horrocks, Polym. Degrad. Stab. 2011, 96, 377.
[2] L. Costes, F. Laoutid, S. Brohez, P. Dubois, Mater. Sci. Eng. Report, R. 2017, 117, 1.
[3] P. Ferruti, J. Polym. Sci, Part A: Polym. Chem. 2013, 51, 2319.
[4] F. Danusso, P. Ferruti, Polymer 1970, 11, 88
Polyamidoamines derived from natural α-amino acids as effective flame retardants for cotton
In this paper, bioinspired polyamidoamines (PAAs) were synthesized from N,N′-methylene bisacrylamide and nine natural α-amino acids: L-alanine, L-valine, L-leucine (M-LEU), L-histidine, L-serine, L-asparagine, L-glutamine (M-GLN), L-aspartic acid and L-glutamic acid (M-GLU) and their performance as flame retardants (FRs) for cotton were determined. The aim was to ascertain if the ability to protect cotton from fire by the process of intumescing, previously found for the glycine-derived M-GLY, was a general feature of α-amino acid-derived PAAs. None of the PAAs ignited by flame impingement, apart from M-LEU, which burned for a few seconds leaving 93% of residue. All of them formed carbon-and oxygen-rich, porous chars with a graphitic structure in the air at 350◦C, as revealed by X-ray photoelectron spectroscopy. All samples were tested as FRs for cotton by horizontal flame spread tests. At a 5% add-on, M-GLU and M-GLN extinguished the flame. The same results were obtained with all the other PAAs at a 7% add-on. The α-amino acid residues influenced the FR performance. The most effective were those that, by heating, were most suitable for producing thermally stable cyclic aromatic structures. All PAA-treated cotton samples, even when burning, left significant residues, which, according to scanning electron microscopy analysis, maintained the original cotton texture
Sulfur-based copolymeric polyamidoamines as efficient flame-retardants for cotton
The polyamidoamine derived from N,N'-methylenebisacrylamide (M) and glycine (G), M-G, has been shown to be an effective flame-retardant (FR) for cotton in horizontal flame spread tests (HFST), extinguishing the flame at 5% add-on. Its activity was attributed to its intrinsic intumescence. In vertical flame spread tests (VFST), M-G failed to extinguish the flame even at 30% add-on. Conversely, in VFST, the polyamidoamine derived from M and cystine (C), M-C, inhibited cotton combustion at 16% add-on, but in HFST failed to extinguish the flame below 12% add-on. Its activity was ascribed to the release of sulfur-containing volatiles acting as radical scavengers. In this work, the FR effectiveness of M-Gm-Cn copolymers with different G/C ratio was compared with that of the M-G and M-C homopolymers and of M-G/M-C blends of the same compositions. In HFST, both copolymers and blends extinguished the flame. In particular, M-G50-C50 and (M-G/M-C)50/50 extinguished the flame, even at 7% add-on. In VFST, the copolymers with 6550% M-C units, similar to M-C, inhibited cotton combustion at 16% add-on. At the same add-on, the M-G/M-C blends failed to extinguish the flame. It may be concluded that, in contrast to blends, copolymers combined the merits of both homopolymers in all tests
Highlight on the Mechanism of Linear Polyamidoamine Degradation in Water
This paper aims at elucidating the degradation mechanism of linear polyamidoamines (PAAs) in water. PAAs are synthesized by the aza-Michael polyaddition of prim-monoamines or bis-sec-amines with bisacrylamides. Many PAAs are water-soluble and warrant potential for biotechnological applications and as flame-retardants. PAAs have long been known to degrade in water at pH 65 7, but their degradation mechanism was never explored in detail. Filling this gap was necessary to assess the suitability of PAAs for the above applications. To this aim, a small library of nine PAAs was expressly synthesized and their degradation mechanism in aqueous solution studied by 1H-NMR in different conditions of pH and temperature. The main degradation mechanism was in all cases the retro-aza-Michael reaction triggered by dilution but, in some cases, hints were detected of concurrent hydrolytic degradation. Most PAAs were stable at pH 4.0; all degraded at pH 7.0 and 9.0. Initially, the degradation rate was faster at pH 9.0 than at pH 7.0, but the percent degradation after 97 days was mostly lower. In most cases, at pH 7.0 the degradation followed first order kinetics. The degradation rates mainly depended on the basicity of the amine monomers. More basic amines acted as better leaving groups
Probing chiral interactions between L- and D-arginine-based polymers and sodium deoxycholate solutions
Nowadays the spontaneous self-organization of a polymer into an ordered structure is a soughtafter property of many smart materials, whose applications might range from catalysis [1] to drugdelivery [2]. However, literature regarding the role played by these specific conformations in chiral recognition remains scarce. In this context, polyamidoamino acids (PAACs) are an emerging class of stimuli-responsive bioinspired synthetic polymers able to self-assemble into pH depend conformations [3,4]. PAACs are an off-spring of polyamidoamines (PAAs), a family of polymers obtained by the Michael-type polyaddition of prim-monoamines or sec-diamines with bisacrylamides. The reaction occurs in aqueous solution at pH = 8\u20139 and at room temperature. By using \u3b1-amino acids as monomers, PAACs are obtained.
The first example of PAAC was named ARGO7, obtained by the stepwise polyaddition in water of L- or D-arginine to N,N\u2019-methylenebisacrylamide. Results indicated Mn 8500, PDI 1.4 and Rh of 1.2 nm [3]. Molecular dynamics (MD) and circular dichroism (CD) showed ARGO7 folded into a rigid structure, reminiscent of the hairpin conformation, solely driven by the polymer main chain. Due to its ability to self-assemble in solution forming chiral structures, L- and D-ARGO7 may selectively interact with biological components.
To assess chiral recognition, sodium deoxycholate (NaDC), one of the components of bile salts, was chosen as a chiral model surface. In aqueous solution, NaDC showed three different pH dependent behaviour: homogeneous solution (pH>8), gel phase (pH 7-8) and aggregation/flocculation (pH<6.5). Notwithstanding the ability of NaDC to self-assemble into different conformations at each pH interval, signs of chiral recognition were found in NaDC gel phase only. Conformational modifications were probed by circular dichroism spectroscopy: both D- and L-ARGO7 changed shape and magnitude of the CD pattern, whereas D,L-ARGO7 did not modify the CD spectra of NaDC. After 8 days, NaDC compact structure loosened, ended up being fluid and the CD pattern were completely modified due to NaDC and D- or L-ARGO7 interactions. Incoming diffusion NMR and SANS studies will probably highlight the mechanisms and dynamics of the chiral interactions in these polyelectrolyte-micelle systems.
[1] Luo, R.; Zhu, M.; Shen, X.; Li, S. J. Catal. 2015, 331, 49. [2] Qui\uf1ones, J. P.; Peniche, H.; Peniche, C. Polymers. 2018, 10, 3, 235. [3] Manfredi, A.; Mauro, N.; Terenzi, A.; Alongi, J.; Lazzari, F.; Ganazzoli, F.; Raffaini, G.; Ranucci, E.; Ferruti, P. ACS Macro Lett. 2017, 6, 987. [4] Lazzari, F.; Manfredi, A.; Alongi, J.; Mendichi, R.; Ganazzoli, F.; Raffaini, G.; Ferruti, P.; Ranucci, E. Polymers 2018, 10, 1261
Chiral recognition in D-, L-arginine derived polyamidoamino acids and sodium deoxycholate solutions
Nowadays the spontaneous self-organization of a polymer into an ordered structure is a sought-after property of many smart materials, whose applications might range from catalysis1 to drug-delivery2. However, literature regarding the role played by these specific conformations in chiral recognition remains scarce. In this context, polyamidoamino acids (PAACs) are an emerging class of stimuli-responsive bioinspired synthetic polymers able to self-assemble into pH depend conformations.3,4 Arginine based PAACs, named ARGO7, were obtained in water at pH 8-9 from the stepwise polyaddition of L- or D-arginine to N,N\u2019methylenebisacrylamide. Results indicated Mn 8500, PDI 1.4 and Rh of 1.2 nm.3 Molecular dynamics (MD) and circular dichroism (CD) showed ARGO7 folded into a rigid structure, reminiscent of the hairpin conformation, solely driven by the polymer main chain. Due to its ability to self-assemble in solution forming chiral structures, L- and D-ARGO7 may selectively interact with biological components. To assess chiral recognition, sodium deoxycholate (NaDC), one of the components of bile salts, was chosen as a chiral model surface. In aqueous solution, NaDC showed three different pH dependent behaviour: homogeneous solution (pH>8), gel phase (pH 7-8) and aggregation/flocculation (pH<6.5). Notwithstanding the ability of NaDC to self-assemble into different conformations at each pH interval, signs of chiral recognition were found in NaDC gel phase only. Conformational modifications were probed by circular dichroism spectroscopy: both D- and L-ARGO7 changed shape and magnitude of the CD pattern, whereas D,LARGO7 did not modify the CD spectra of NaDC. After 8 days, NaDC compact structure loosened, ended up being fluid and the CD pattern were completely modified due to NaDC and D- or L-ARGO7 interactions. Incoming SANS studies will probably highlight the mechanisms and dynamics of the chiral interactions in these polyelectrolyte-micelle systems.
(1) Luo, R.; Zhu, M.; Shen, X.; Li, S. J. Catal. 2015, 331, 49. (2) Qui\uf1ones, J. P.; Peniche, H.; Peniche, C. Polymers. 2018, 10, 3, 235. (3) Manfredi, A.; Mauro, N.; Terenzi, A.; Alongi, J.; Lazzari, F.; Ganazzoli, F.; Raffaini, G.; Ranucci, E.; Ferruti, P. ACS Macro Lett. 2017, 6, 987. (4) Lazzari, F.; Manfredi, A.; Alongi, J.; Mendichi, R.; Ganazzoli, F.; Raffaini, G.; Ferruti, P.; Ranucci, E. Polymers 2018, 10, 1261
Sericin-based resins from silk degumming wastewater for the removal of heavy metal ions from water
Chromium (VI) is a water pollutant categorized as \u2018likely to be a carcinogen to humans\u2019 compound when orally ingested with estimated cancer potency 0.5 mg/kg/day. The European Directive 2001/59/EC poses a 5 \ub5g/L threshold concentration for Cr(VI) in groundwaters. In this work, a chemical process was devised to obtain heavy metal ion absorbing resins by the polyaddition of bisacrylamides and 1,2-diaminoethane with sericin using as reaction solvent raw waste-water from silk degumming processes. Silk sericin (SS) is a natural globural protein deriving from silk worm Bombyx mori with molecular weight ranging from 10000 to 300000. Following the alkaline degumming process, sericin is degraded to peptides with molecular weight 20000. These peptides contain lysine-deriving residues that participate in the polyaddition leaving to a resin. This resin is a hybrid one in which a substantial portion is constituted by sericin peptides. The rationale of this approach is that the guanidinum ion has the ability to strongly bind oxoanions, due to its geometrical Y-shaped, planar orientation, optimizing charge distribution and hydrogen bonds [1]. SS resins were evaluated for the removal of both positively charged (Cu2+, Co2+, Ni2+, Mn2+) and negatively charged heavy metals oxoanions (CrO42-) from water. Different resins were obtained containing different amounts of sericin. These resins were characterized by elemental analysis and their structure confirmed by FT-IR/ATR spectroscopy. The swelling capacity of the new absorbents in different media and their thermal stability by DSC and TGA techniques were evaluated. The removal properties of resins towards Cu2+, Co2+, Ni2+, Mn2+ and CrO42- ions in aqueous single metal dilute and concentrate solutions were performed in batch absorption experiments and evaluated by EDTA titration in the case of Cu2+, Co2+, Ni2+, Mn2+, and by the UV-VIS spectroscopy in the case of CrO42-. The products showed different absorption capacities depending on the SS content in the resin. Treatment with 0.1 M HCl showed excellent regeneration with maintenance of the resins absorption capacity for 20 regeneration cycles.
In conclusion, sericin-based resins, besides being biocompatible, were endowed with environmental friendly preparation process; biodegradability; moderate cost; ability to fast and quantitatively absorb from aqueous solutions even at low pollutant concentration; full reversibility of the absorption process making it economically convenient both for regeneration and metal recovery
Superior flame retardancy of cotton by synergetic effect of cellulose-derived nano-graphene oxide carbon dots and disulphide-containing polyamidoamines
Linear polyamidoamines containing disulphide groups (SS-PAAs) were prepared by polyaddition of L-cystine with 2,2-bisacrylamidoacetic acid (B-CYSS), N,N\u2032-methylenebisacrylamide (M-CYSS) and 1,4-bisacryloylpiperazine (BP-CYSS). They were evaluated as flame retardants for cotton, alone or with cellulose-derived nano-graphene oxide (nGO) carbon dots, to assess whether, due to their potential as radical scavengers, the latter would improve the already good performance of SS-PAAs. In vertical flame spread tests (VFST), cotton treated with 1% nGO burned as quickly as cotton, whereas B-CYSS, M-CYSS and BP-CYSS extinguished the flame at add-ons 65 12, 16 and 20%, respectively. Probably, the gaseous products of SS-PAA thermal degradation quenched the radicals involved in oxidation. Cotton treated with 8, 12 and 15%, respectively, of B-CYSS, M-CYSS and BP-CYSS burned completely, but further addition of 1% nGO either inhibited ignition or shortly extinguished the flame, demonstrating synergism between the two components. Synergism was confirmed by assessing the synergism effectiveness parameter for the residual mass fraction (RMF) and by comparing the calculated and experimental TG curves in air for the cotton/SS-PAA-nGO systems. In cone calorimetry tests, the presence of nGO did not improve the already good performances of SS-PAAs, supporting the hypothesis that the action of both takes place in the gas phase
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