Proton MR spectroscopy in quantitative in vivo determination of fat content in human liver steatosis

To demonstrate that the lipid volume fraction in liver steatosis can be accurately estimated with in vivo hydrogen-1 magnetic resonance (MR) spectroscopy, the authors developed a calibration procedure based on in vitro MR spectroscopy of lipid extracts from steatotic liver specimens. The lipid volume fractions determined with the calibration procedure were compared with the results of histomorphometry and with calibrated computed tomographic (CT) data. The volume fraction of fat determined with MR spectroscopy was in good agreement with the CT results, whereas histomorphometry underestimated the amount of hepatic fat. The results indicate that determination of the fat volume fraction in steatotic liver can be achieved noninvasively with MR spectroscopy.

Noninvasive in vivo quantitative assessment of fat content in human liver

BACKGROUND/AIMS

Since the introduction of ultrasonography, liver steatosis has become an increasingly frequent diagnosis. Both ultrasonography (US) and computerized tomography (CT) provide qualitative rather than quantitative assessment of fatty infiltration. The objective of this study was to develop a noninvasive method for the quantification of the hepatic fat content in vivo. A test object containing solutions with CT scan density (CTD) similar to normal liver ("liver-equivalent") or "fat-equivalent material" in variable proportions was prepared to measure patients with variable degrees of steatosis in vivo.

RESULTS

A linear correlation (r=0.99, p<0.001) linked CTD and the increasing percentage of fat-equivalent material. A CTD calibration curve was derived as a reference for the in vivo determinations. In 29 consecutive patients with steatosis diagnosed by histology, CTD was linearly correlated (r=0.83, p<0.001) with the hepatic fat content (HFC) expressed as percent of the whole liver, obtained by a computerized histomorphometric analysis. Based on the calibration curve obtained in 29 subjects who underwent liver biopsy, 38 additional consecutive steatotic patients were examined and the degree of hepatic fat content was calculated. The HFC was linearly correlated (r=-0.86, p<0.001) with the liver-to-spleen ratio.

CONCLUSIONS

We conclude that the use of test objects allows an accurate and reproducible noninvasive quantitative assessment of hepatic fat infiltration in humans. This technique may prove useful in the evaluation of the natural course and treatment of hepatic steatosis as well as in the assessment of donor livers prior to transplantation.

A newly generated functional antibody identifies Tn antigen as a novel determinant in the cancer cell-lymphatic endothelium interaction

Malignant transformation of epithelial cells is frequently associated with the alteration of glycosylation pathways. Tn is a common tumor-associated carbohydrate antigen present in 90% of human carcinomas and its expression correlates with metastatic potential and poor prognosis. Despite its relevance, the functional role of Tn in tumor biology has not been firmly established probably for the lack of appropriate experimental tools. Our aims were to produce highly reactive monoclonal antibodies against Tn making use of synthetically produced Tn and to test their usefulness for in vivo imaging as well as to define their potential functional activity in tumor cell spread. We immunized mice with Tn clustered on cationized BSA and screened the positive hybridomas with Tn-biotinylated alginate. Enzyme-linked immuno sorbent assay and immunofluorescence assays revealed that the most reactive anti-Tn IgM mAb (2154F12A4) selectively recognized Tn on the MCF7 breast cancer cell line since its binding to the cell membrane was completely abolished by preincubation with purified Tn. Importantly, QDot 800-conjugated mAb injected in MCF7-tumor bearing mice specifically bound to primary tumor lesions as well as to metastases in lymph nodes. In addition, this mAb was able to inhibit cancer cell adhesion to lymphatic endothelium suggesting a novel involvement of Tn in the lymphatic dissemination of cancer cells and hypothesizing future applications in inhibiting lymphatic metastases.

John J, Sulak L, Zou D, Alimena J, Berry E, Bhattacharya S, Cutts D, Dhingra N, Ferapontov A, Garabedian A, Hakala J, Heintz U, Laird E, Landsberg G, Mao Z, Narain M, Piperov S, Sagir S, Syarif R, Breedon R, Breto G, De La Barca Sanchez MC, Chauhan S, Chertok M, Conway J, Conway R, Cox PT, Erbacher R, Funk G, Gardner M, Ko W, Lander R, Mulhearn M, Pellett D, Pilot J, Ricci-Tam F, Shalhout S, Smith J, Squires M, Stolp D, Tripathi M, Wilbur S, Yohay R, Bravo C, Cousins R, Everaerts P, Farrell C, Florent A, Hauser J, Ignatenko M, Saltzberg D, Schnaible C, Valuev V, Weber M, Burt K, Clare R, Ellison J, Gary JW, Hanson G, Heilman J, Ivova PANEVA M, Jandir P, Kennedy E, Lacroix F, Long OR, Luthra A, Malberti M, Negrete MO, Shrinivas A, Wei H, Wimpenny S, Yates BR, Branson JG, Cerati GB, Cittolin S, D’Agnolo RT, Derdzinski M, Holzner A, Kelley R, Klein D, Letts J, Macneill I, Olivito D, Padhi S, Pieri M, Sani M, Sharma V, Simon S, Tadel M, Tu Y, Vartak A, Wasserbaech S, Welke C, Würthwein F, Yagil A, Zevi Della Porta G, Bradmiller-Feld J, Campagnari C, Dishaw A, Dutta V, Flowers K, Franco Sevilla M, Geffert P, George C, Golf F, Gouskos L, Gran J, Incandela J, Mccoll N, Mullin SD, Mullin SD, Richman J, Stuart D, Suarez I, West C, Yoo J, Anderson D, Apresyan A, Bornheim A, Bunn J, Chen Y, Duarte J, Mott A, Newman HB, Pena C, Pierini M, Spiropulu M, Vlimant JR, Xie S, Zhu RY, Andrews MB, Azzolini V, Calamba A, Carlson B, Ferguson T, Paulini M, Russ J, Sun M, Vogel H, Vorobiev I, Cumalat JP, Ford WT, Gaz A, Jensen F, Johnson A, Krohn M, Mulholland T, Nauenberg U, Stenson K, Wagner SR, Alexander J, Chatterjee A, Chaves J, Chu J, Dittmer S, Eggert N, Mirman N, Nicolas Kaufman G, Patterson JR, Rinkevicius A, Ryd A, Skinnari L, Soffi L, Sun W, Tan SM, Teo WD, Thom J, Thompson J, Tucker J, Weng Y, Wittich P, Abdullin S, Albrow M, Apollinari G, Banerjee S, Bauerdick LAT, Beretvas A, Berryhill J, Bhat PC, Bolla G, Burkett K, Butler JN, Cheung HWK, Chlebana F, Cihangir S, Elvira VD, Fisk I, Freeman J, Gottschalk E, Gray L, Green D, Grünendahl S, Gutsche O, Hanlon J, Hare D, Harris RM, Hasegawa S, Hirschauer J, Hu Z, Jayatilaka B, Jindariani S, Johnson M, Joshi U, Jung AW, Klima B, Kreis B, Lammel S, Linacre J, Lincoln D, Lipton R, Liu T, Lopes De Sá R, Lykken J, Maeshima K, Marraffino JM, Martinez Outschoorn VI, Maruyama S, Mason D, McBride P, Merkel P, Mishra K, Mrenna S, Nahn S, Newman-Holmes C, O’Dell V, Pedro K, Prokofyev O, Rakness G, Sexton-Kennedy E, Soha A, Spalding WJ, Spiegel L, Strobbe N, Taylor L, Tkaczyk S, Tran NV, Uplegger L, Vaandering EW, Vernieri C, Verzocchi M, Vidal R, Weber HA, Whitbeck A, Acosta D, Avery P, Bortignon P, Bourilkov D, Carnes A, Carver M, Curry D, Das S, Field RD, Furic IK, Gleyzer SV, Hugon J, Konigsberg J, Korytov A, Kotov K, Low JF, Ma P, Matchev K, Mei H, Milenovic P, Mitselmakher G, Rank D, Rossin R, Shchutska L, Snowball M, Sperka D, Terentyev N, Thomas L, Wang J, Wang S, Yelton J, Hewamanage S, Linn S, Markowitz P, Martinez G, Rodriguez JL, Adams JR, Ackert A, Adams T, Askew A, Bein S, Bochenek J, Diamond B, Haas J, Hagopian S, Hagopian V, Johnson KF, Khatiwada A, Prosper H, Weinberg M, Baarmand MM, Bhopatkar V, Colafranceschi S, Hohlmann M, Kalakhety H, Noonan D, Roy T, Yumiceva F, Adams MR, Apanasevich L, Berry D, Betts RR, Bucinskaite I, Cavanaugh R, Evdokimov O, Gauthier L, Gerber CE, Hofman DJ, Kurt P, O’Brien C, Sandoval Gonzalez LD, Silkworth C, Turner P, Varelas N, Wu Z, Zakaria M, Bilki B, Clarida W, Dilsiz K, Durgut S, Gandrajula RP, Haytmyradov M, Khristenko V, Merlo JP, Mermerkaya H, Mestvirishvili A, Moeller A, Nachtman J, Ogul H, Onel Y, Ozok F, Penzo A, Snyder C, Tiras E, Wetzel J, Yi K, Anderson I, Anderson I, Barnett BA, Blumenfeld B, Eminizer N, Fehling D, Feng L, Gritsan AV, Maksimovic P, Martin C, Osherson M, Roskes J, Sady A, Sarica U, Swartz M, Xiao M, Xin Y, You C, Xiao M, Baringer P, Bean A, Benelli G, Bruner C, Kenny RP, Majumder D, Majumder D, Malek M, Murray M, Sanders S, Stringer R, Wang Q, Ivanov A, Kaadze K, Khalil S, Makouski M, Maravin Y, Mohammadi A, Saini LK, Skhirtladze N, Toda S, Lange D, Rebassoo F, Wright D, Anelli C, Baden A, Baron O, Belloni A, Calvert B, Eno SC, Ferraioli C, Gomez JA, Hadley NJ, Jabeen S, Jabeen S, Kellogg RG, Kolberg T, Kunkle J, Lu Y, Mignerey AC, Shin YH, Skuja A, Tonjes MB, Tonwar SC, Apyan A, Barbieri R, Baty A, Bierwagen K, Brandt S, Bierwagen K, Busza W, Cali IA, Demiragli Z, Di Matteo L, Gomez Ceballos G, Goncharov M, Gulhan D, Iiyama Y, Innocenti GM, Klute M, Kovalskyi D, Lai YS, Lee YJ, Levin A, Luckey PD, Marini AC, Mcginn C, Mironov C, Narayanan S, Niu X, Paus C, Ralph D, Roland C, Roland G, Salfeld-Nebgen J, Stephans GSF, Sumorok K, Varma M, Velicanu D, Veverka J, Wang J, Wang TW, Wyslouch B, Yang M, Zhukova V, Dahmes B, Evans A, Finkel A, Gude A, Hansen P, Kalafut S, Kao SC, Klapoetke K, Kubota Y, Lesko Z, Mans J, Nourbakhsh S, Ruckstuhl N, Rusack R, Tambe N, Turkewitz J, Acosta JG, Oliveros S, Avdeeva E, Bloom K, Bose S, Claes DR, Dominguez A, Fangmeier C, Gonzalez Suarez R, Kamalieddin R, Keller J, Knowlton D, Kravchenko I, Meier F, Monroy J, Ratnikov F, Siado JE, Snow GR, Alyari M, Dolen J, George J, Godshalk A, Harrington C, Iashvili I, Kaisen J, Kharchilava A, Kumar A, Rappoccio S, Roozbahani B, Alverson G, Barberis E, Baumgartel D, Chasco M, Hortiangtham A, Massironi A, Morse DM, Nash D, Orimoto T, Teixeira De Lima R, Trocino D, Wang RJ, Wood D, Zhang J, Hahn KA, Kubik A, Mucia N, Odell N, Pollack B, Pozdnyakov A, Schmitt M, Stoynev S, Sung K, Trovato M, Velasco M, Brinkerhoff A, Dev N, Hildreth M, Jessop C, Karmgard DJ, Kellams N, Lannon K, Marinelli N, Meng F, Mueller C, Musienko Y, Planer M, Reinsvold A, Ruchti R, Smith G, Taroni S, Valls N, Wayne M, Wolf M, Woodard A, Antonelli L, Brinson J, Bylsma B, Durkin LS, Flowers S, Hart A, Hill C, Hughes R, Ji W, Ling TY, Liu B, Luo W, Puigh D, Rodenburg M, Winer BL, Wulsin HW, Driga O, Elmer P, Hardenbrook J, Hebda P, Koay SA, Lujan P, Marlow D, Medvedeva T, Mooney M, Olsen J, Palmer C, Piroué P, Saka H, Stickland D, Tully C, Zuranski A, Malik S, Barnes VE, Benedetti D, Bortoletto D, Gutay L, Jha MK, Jones M, Jung K, Miller DH, Neumeister N, Primavera F, Radburn-Smith BC, Shi X, Shipsey I, Silvers D, Sun J, Svyatkovskiy A, Wang F, Xie W, Xu L, Parashar N, Stupak J, Adair A, Akgun B, Chen Z, Ecklund KM, Geurts FJM, Guilbaud M, Li W, Michlin B, Northup M, Padley BP, Redjimi R, Roberts J, Rorie J, Tu Z, Zabel J, Betchart B, Bodek A, de Barbaro P, Demina R, Eshaq Y, Ferbel T, Galanti M, Galanti M, Garcia-Bellido A, Han J, Harel A, Hindrichs O, Hindrichs O, Khukhunaishvili A, Petrillo G, Tan P, Verzetti M, Arora S, Barker A, Chou JP, Contreras-Campana C, Contreras-Campana E, Ferencek D, Gershtein Y, Gray R, Halkiadakis E, Hidas D, Hughes E, Kaplan S, Kunnawalkam Elayavalli R, Lath A, Nash K, Panwalkar S, Park M, Salur S, Schnetzer S, Sheffield D, Somalwar S, Stone R, Thomas S, Thomassen P, Walker M, Foerster M, Riley G, Rose K, Spanier S, York A, Bouhali O, Castaneda Hernandez A, Celik A, Dalchenko M, De Mattia M, Delgado A, Dildick S, Dildick S, Eusebi R, Gilmore J, Huang T, Kamon T, Krutelyov V, Krutelyov V, Mueller R, Osipenkov I, Pakhotin Y, Patel R, Patel R, Perloff A, Rose A, Safonov A, Tatarinov A, Ulmer KA, Akchurin N, Cowden C, Damgov J, Dragoiu C, Dudero PR, Faulkner J, Kunori S, Lamichhane K, Lee SW, Libeiro T, Undleeb S, Volobouev I, Appelt E, Delannoy AG, Greene S, Gurrola A, Janjam R, Johns W, Maguire C, Mao Y, Melo A, Ni H, Sheldon P, Snook B, Tuo S, Velkovska J, Xu Q, Arenton MW, Cox B, Francis B, Goodell J, Hirosky R, Ledovskoy A, Li H, Lin C, Neu C, Sinthuprasith T, Sun X, Wang Y, Wolfe E, Wood J, Xia F, Clarke C, Harr R, Karchin PE, Kottachchi Kankanamge Don C, Lamichhane P, Sturdy J, Belknap DA, Carlsmith D, Cepeda M, Dasu S, Dodd L, Duric S, Gomber B, Grothe M, Hall-Wilton R, Herndon M, Hervé A, Klabbers P, Lanaro A, Levine A, Long K, Loveless R, Mohapatra A, Ojalvo I, Perry T, Pierro GA, Polese G, Ruggles T, Sarangi T, Savin A, Sharma A, Smith N, Smith WH, Taylor D, Woods N. Event generator tunes obtained from underlying event and multiparton scattering measurements

New sets of parameters ("tunes") for the underlying-event (UE) modelling of the pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE proton-proton ([Formula: see text]) data at [Formula: see text] and to UE proton-antiproton ([Formula: see text]) data from the CDF experiment at lower [Formula: see text], are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton-proton collisions at 13[Formula: see text]. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to "minimum bias" (MB) events, multijet, and Drell-Yan ([Formula: see text] lepton-antilepton+jets) observables at 7 and 8[Formula: see text], as well as predictions for MB and UE observables at 13[Formula: see text].

The aggregation of pig articular chondrocyte and synthesis of extracellular matrix by a lactose-modified chitosan

A reductive amination reaction (N-alkylation) obtained exploiting the aldheyde group of lactose and the amino group of the glucosamine residues of chitosan (d.a. 89%) afforded a highly soluble engineered polysaccharide (chitlac) for a potential application in the repair of the articular cartilage. Chitosan derivatives with 9% and 64% of side chain groups introduced have been prepared and characterized by means of potentiometric titration, (1)H-NMR and intrinsic viscosity. Both polymers, with respect to the unmodified chitosan, induce cell aggregation when in contact with a primary culture of pig chondrocytes, leading to the formation of nodules of considerable dimensions (up to 0.5-1 mm in diameter). The nodules obtained from chondrocytes treated with chitlac with the higher degree of substitution have been studied by means of optical and electron microscopy (SEM, TEM) and the production of glycosaminoglycans (GAGs) and collagen has been measured by means of colorimetric assays. The chondro-specificity of GAG and collagen was determined by RT-PCR. The results show that the lactose-modified chitosan is non-toxic and stimulates the production of aggrecan and type II collagen.

Adhesive and sealant interfaces for general surgery applications

The main functions of biological adhesives and sealants are to repair injured tissues, reinforce surgical wounds, or even replace common suturing techniques. In general surgery, adhesives must match several requirements taking into account clinical needs, biological effects, and material features; these requirements can be fulfilled by specific polymers. Natural or synthetic polymeric materials can be employed to generate three-dimensional networks that physically or chemically bind to the target tissues and act as hemostats, sealants, or adhesives. Among them, fibrin, gelatin, dextran, chitosan, cyanoacrylates, polyethylene glycol, and polyurethanes are the most important components of these interfaces; various aspects regarding their adhesion mechanisms, mechanical performance, and resistance to body fluids should be taken into account to choose the most suitable formulation for the target application. This review aims to describe the main adhesives and sealant materials for general surgery applications developed in the past decades and to highlight the most important aspects for the development of future formulations.

Alginate/lactose-modified chitosan hydrogels: a bioactive biomaterial for chondrocyte encapsulation

A new bioactive scaffold was prepared from a binary polysaccharide mixture composed of a polyanion (alginate) and a polycation (a lactose-modified chitosan, chitlac). Its potential use for articular chondrocytes encapsulation and cartilage reconstructive surgery applications has been studied. The hydrogel combines the ability of alginate to act as a 3D supporting structure with the capability of the second component (chitlac) to provide interactions with porcine articular chondrocytes. Physico-chemical characterization of the scaffold was accomplished by gel kinetics and compression measurements and demonstrated that alginate-chitlac mixture (AC-mixture) hydrogels exhibit better mechanical properties when compared with sole alginate hydrogels. Furthermore, biochemical and biological studies showed that these 3D scaffolds are able to maintain chondrocyte phenotype and particularly to significantly stimulate and promote chondrocyte growth and proliferation. In conclusion, the present study can be considered as a first step towards an engineered, biologically active scaffold for chondrocyte in vitro cultivation, expansion, and cell delivery.

Chemical imaging of articular cartilage sections with Raman mapping, employing uni- and multi-variate methods for data analysis

Raman mapping in combination with uni- and multi-variate methods of data analysis is applied to articular cartilage samples. Main differences in biochemical composition and collagen fibers orientation between superficial, middle and deep zone of the tissue are readily observed in the samples. Collagen, non-collagenous proteins, proteoglycans and nucleic acids can be distinguished on the basis of their different spectral characteristics, and their relative abundance can be mapped in the label-free tissue samples, at so high a resolution as to permit the analysis at the level of single cells. Differences between territorial and inter-territorial matrix, as well as inhomogeneities in the inter-territorial matrix, are properly identified. Multivariate methods of data analysis prove to be complementary to the univariate approach. In particular, our partial least squares regression model gives a semiquantitative mapping of the biochemical constituents in agreement with average composition found in the literature. The combination of hierarchical and fuzzy cluster analysis succeeds in detecting variations between different regions of the extra-cellular matrix. Because of its characteristics as an imaging technique, Raman mapping could be a promising tool for studying biochemical changes in cartilage occurring during aging or osteoarthritis.

Extraction and validation of a new set of CMS pythia8 tunes from underlying-event measurements

New sets of CMS underlying-event parameters ("tunes") are presented for the pythia8 event generator. These tunes use the NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Measurements of charged-particle multiplicity and transverse momentum densities at various hadron collision energies are fit simultaneously to determine the parameters of the tunes. Comparisons of the predictions of the new tunes are provided for observables sensitive to the event shapes at LEP, global underlying event, soft multiparton interactions, and double-parton scattering contributions. In addition, comparisons are made for observables measured in various specific processes, such as multijet, Drell-Yan, and top quark-antiquark pair production including jet substructure observables. The simulation of the underlying event provided by the new tunes is interfaced to a higher-order matrix-element calculation. For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.

Transverse-momentum and pseudorapidity distributions of charged hadrons in pp collisions at square root of s = 7 TeV

Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at square root of s = 7  TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dN(ch)/dη|(|η|<0.5) = 5.78 ± 0.01(stat) ± 0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from square root of s = 0.9 to 7 TeV is [66.1 ± 1.0(stat) ± 4.2(syst)]%. The mean transverse momentum is measured to be 0.545 ± 0.005(stat) ± 0.015(syst)  GeV/c. The results are compared with similar measurements at lower energies.

Concepts for Developing Physical Gels of Chitosan and of Chitosan Derivatives

Chitosan macro- and micro/nano-gels have gained increasing attention in recent years, especially in the biomedical field, given the well-documented low toxicity, degradability, and non-immunogenicity of this unique biopolymer. In this review we aim at recapitulating the recent gelling concepts for developing chitosan-based physical gels. Specifically, we describe how nowadays it is relatively simple to prepare networks endowed with different sizes and shapes simply by exploiting physical interactions, namely (i) hydrophobic effects and hydrogen bonds-mostly governed by chitosan chemical composition-and (ii) electrostatic interactions, mainly ensured by physical/chemical chitosan features, such as the degree of acetylation and molecular weight, and external parameters, such as pH and ionic strength. Particular emphasis is dedicated to potential applications of this set of materials, especially in tissue engineering and drug delivery sectors. Lastly, we report on chitosan derivatives and their ability to form gels. Additionally, we discuss the recent findings on a lactose-modified chitosan named Chitlac, which has proved to form attractive gels both at the macro- and at the nano-scale.

Culture and differentiation of chondrocytes entrapped in alginate gels

We studied the response to culture conditions and the differentiative ability in suspension culture in alginate gels of resting chondrocytes from the preosseous cartilage of adult pig scapula. It was found that the maximum rate of chondrocyte duplication is reached at the fourth day in culture whereas the rate of proteoglycan synthesis and alkaline phosphatase expression do not gain a maximum value before the seventh day. During the culture time, the chondrocytes undergo differentiation as it is demonstrated by the alkaline phosphatase specific activity increase and by morphological criteria (hypertrophy, increase of the number of mitochondria per cell, increased endoplasmic reticulum, matrix vesicle production). The alginate gels can be easily dissolved to obtain cell populations in which the variation of cytosolic calcium concentration following a proliferative stimulus can be conveniently observed using the conventional procedure of Fura 2.

Synthesis, characterization, and preliminary biological study of glycoconjugates of poly(styrene-co-maleic acid)

Three derivatives of the biocompatible polymer poly(styrene-co-maleic anhydride) (SMA) were obtained with 1-amino-1-deoxy-beta-D-galactose, 1-amino-1-deoxy-beta-D-glucose, and 1-amino-1-deoxy-beta-D-lactose, respectively. The amino sugars were chemically conjugated via formation of an amide bond between the anomeric amino group of the sugar residue and the anhydride of the copolymer, giving the corresponding glycoconjugate derivatives. Colorimetric assay of the unreacted amino groups and elemental analysis were used to determine the degree of substitution. About 56%, 54%, and 94% of the available anhydride groups reacted to give galactosyl-amide (SMA-Gal), glucosyl-amide (SMA-Gluc), and lactosyl-amide (SMA-Lac) branched polymers, respectively. The synthesized glycopolymers were characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, circular dichroism, and UV and fluorescence spectroscopy. The release of glucosylamine from the glucosyl-amide branched polymer, by basic hydrolysis, was monitored by high-performance anion-exchange chromatography and by capillary electrophoresis, providing for an additional check of the degree of substitution of this specific polymer derivative. Biological activity tests showed that both SMA-Gal and SMA-Lac allow adhesion of HepG2 hepatic cells about five times larger than that of hydrolyzed, underivatized SMA.

Biological responses of silver-coated thermosets: an in vitro and in vivo study

Bisphenol A glycidylmethacrylate (BisGMA)/triethyleneglycol dimethacrylate (TEGDMA) thermosets are biomaterials commonly employed for orthopedic and dental applications; for both these fields, bacterial adhesion to the surface of the implant represents a major issue for the outcome of the surgical procedures. In this study, the antimicrobial properties of a nanocomposite coating formed by polysaccharide 1-deoxylactit-1-yl chitosan (Chitlac) and silver nanoparticles (nAg) on methacrylate thermosets were studied. The Chitlac-nAg system showed good anti-bacterial and anti-biofilm activity although its biocidal properties can be moderately, albeit significantly, inhibited by serum proteins. In vitro studies on the silver release kinetic in physiological conditions showed a steady metal release associated with a gradual loss of antimicrobial activity. However, after 3weeks there was still effective protection against bacterial colonization which could be accounted for by the residual silver. This time-span could be considered adequate to confer short-term protection from early peri-implant infections. Preliminary in vivo tests in a mini-pig animal model showed good biological compatibility of Chitlac-nAg-coated materials when implanted in bony tissue. The comparison was made with implants of titanium Ti6Al4V alloy and with a Chitlac-coated thermoset. Bone healing patterns and biocompatibility parameters observed for nAg-treated material were comparable with those observed for control implants.

Nano-composite scaffolds for bone tissue engineering containing silver nanoparticles: preparation, characterization and biological properties

In this study nano-composite scaffolds to be used as bone grafts have been endowed with antibacterial properties owing to the presence of silver nanoparticles. The alginate/hydroxyapatite composite scaffolds were prepared by internal gelation followed by a freeze-drying procedure to obtain a porous structure. The nanoparticles were prepared in presence of a lactose modified-chitosan and this colloidal solution was adsorbed on the scaffolds by exploiting electrostatic interactions. The adsorption and release of the silver from the composite scaffold was measured by ICP-AES and spectrofluorimetry measurements. Micro-computed tomography analysis of the scaffolds showed a homogeneous porous structure with average pore sizes of 341.5 μm and porosity of 80 %. In vitro biological tests (MTS and killing kinetics assays) demonstrated that silver does not affect the ability of the scaffolds to promote osteoblasts proliferation and that at the same time it exerts a strong bactericidal effect against both Gram+ and Gram- bacterial strains. Overall, the combined results indicate that these biocompatible antimicrobial scaffolds possess ideal characteristics for tissue engineering applications.

Biological response of hydrogels embedding gold nanoparticles

A nanocomposite hydrogel based on natural polysaccharides and gold nanoparticles (ACnAu) has been prepared and its biological effects were tested in vitro with both bacteria and eukaryotic cells. Antimicrobial tests showed that AC-nAu gels are effective in killing both gram+ (Staphylococcus aureus) and gram- (Pseudomonas aeruginosa) bacteria. LDH assays pointed at a toxic effect towards eukaryotic cell-lines (HepG2 and MG63), in contrast with the case of silver-based hydrogels; cytofluorimetry studies demonstrated an apoptosis-related mechanism induced by increase of ROS intracellular level which leads to cell death after 24 h of direct contact with AC-nAu gels. In vivo biocompatibility has been evaluated in a rat model, investigating the peri-implant soft tissue reaction after 1 month of implantation. The results show that silver-containing samples induced a fibrotic capsule of the same average thickness of the control sample (devoid of nanoparticles) (∼50 μm), while in the case of gold containing materials the fibrotic capsule was thicker (∼100 μm), confirming a higher biocompatibility for silver-based samples than for gold-based ones.