Use of atomic force microscopy for characterization of model membranes and cells

Background: To provide a fundamental understanding of the potential and use of atomic force microscopy (AFM) in medicine and the life sciences, this work presents a thorough description of imaging and non-imaging atomic force microscopy modes for characterizing model membranes and cells at the nanoscale. Methods: The imaging and non-imaging AFM modes are described with examples in terms of the characterization of topographic, morphological, and nanomechanical sample properties. Results: AFM imaging of supported lipid bilayers (SLBs) revealed the effects of temperature and medium composition on SLB topography in the gel and fluid phases, and on the bilayer thickness. Non-imaging AFM showed the strengthening of the SLB in both phases by the ion binding process.Imaging of neuronal and neuroblastoma cells with and without treatment revealed morphological changes in shape, volume, roughness, and Feret dimension. Non-imaging AFM showed the change in cell elasticity induced by the treatment with H2O2 with and without quercetin and by the treatment with copper and myricetin. The measurements of cells elasticity revealed a reorganization of the cytoskeleton and filament structures. Conclusions: Diverse applications of imaging and non-imaging AFM can provide important information about the underlying processes in biologically relevant systems. AFM, as a complementary technique to other biomedical methods, allows screening and monitoring of physiological changes at the nanoscale

Self-similarity of molecular association in double layers

Asocijacija molekula površinski aktivnih tvari (PAT), rast i agregacija samoasocijata u lamelarne dvoslojeve (fleksibilne i zatvorene), micele, vezikule i tekuće kristale, predstavljaju važna temeljna istraživanja s primjenom - između ostalog - na transmembranska svojstva vezikula u prijenosu i enkapsulaciji lijekova. Među mnogim praktičnim upotrebama amfifilni agregati predstavljaju mogućnost primjene dobro definiranih dvoslojeva i multislojeva liotropnih mezotaza za kozmetičku i faimaceutsku industriju. Asocijati katanionskih PAT pokazuju široku raznovrsnost oblika, veličina i strukture čestica pa je moguće proizvesti nove materijale različitih svojstava. Vezikule mogu nastajati spontano kao rezultat samo nakupljanja fleksibilnih monoslojeva u jednoslojne i višeslojne meke čestice sa zatvorenim dvoslojevima. U ovom radu istraživanja su provedena u katanionskim smjesama natrijevoga n dodecilbenzensulfonata (SDBS) i didodecildimetil amonijevoga bromida (DDAB) u vodi te u vodenim otopinama neionskoga dvolančanog PAT, 4-(l-pentilheptil)benzensulfonata (6SDBS). Određivanje faznoga dijagrama, područja stvaranja micela i vezikula te faznih prijelaza, određivanje unutarnjih i vanjskih struktura čestica, provedeno je s pomoću metode raspršenja svjetlosti, raspršenja X zraka pod malim kutom te drugih komplementarnih metoda, npr. reoloških mjerenja u pseudo-izotropnim područjima koja dobro indiciraju stvaranje micela i vezikula karakterizirano kritičnim micelizacijskim i vezikularnim koncentracijama. Dodatno, mezofaze su istraživane polarizacijskom i elektronskom mikroskopijom.Surfactant molecules association, growth and aggregation of selt associates into lamellar bilayers (flexible and closed), micelles, vesicles and liquid crystals, is considered to present important fundamental research with application to trans-membrane properties in the drug delivery and encapsulation. Among many practical applications, the amphiphilic aggregates present the possibility of using well defined bilayers and multilayers in the cosmetic and pharmaceutical industry. Associates of catanionic surfactants show a wide variety of particle shapes, sizes and structures, and due to that, the new materials of different properties could be prepared. Vesicles can be formed spontaneously as a result of self-association of flexible monolayers into unilamellar and multilamellar soft particles with closed bilayers. In this paper investigations have been performed in catanionic mixtures of Sodium n-dodecylbenzensulfonate (SDBS) and Didodecyldimetyl ammonium bromide (DDAB) in water, and in the water solutions of nonionic double-chain surfactant, 4-( 1 pentylheptyl)benzenesulfonate (6SDBS). Phase diagram, regions of micelles and vesicles formation, phase transitions, outer and inner structures of particles, were investigated by light scattering, small angle X-ray scattering, and other related methods, e.g., rheological measurements within pseudoisotropic regions that indicated the formation of micelles and vesicles as characterised by the critical micellisation and vesiculation concentrations. In addition, mesophases have been confirmed by polarisation and electron microscopy

Self-similarity of molecular association in double layers

Asocijacija molekula površinski aktivnih tvari (PAT), rast i agregacija samoasocijata u lamelarne dvoslojeve (fleksibilne i zatvorene), micele, vezikule i tekuće kristale, predstavljaju važna temeljna istraživanja s primjenom - između ostalog - na transmembranska svojstva vezikula u prijenosu i enkapsulaciji lijekova. Među mnogim praktičnim upotrebama amfifilni agregati predstavljaju mogućnost primjene dobro definiranih dvoslojeva i multislojeva liotropnih mezotaza za kozmetičku i faimaceutsku industriju. Asocijati katanionskih PAT pokazuju široku raznovrsnost oblika, veličina i strukture čestica pa je moguće proizvesti nove materijale različitih svojstava. Vezikule mogu nastajati spontano kao rezultat samo nakupljanja fleksibilnih monoslojeva u jednoslojne i višeslojne meke čestice sa zatvorenim dvoslojevima. U ovom radu istraživanja su provedena u katanionskim smjesama natrijevoga n dodecilbenzensulfonata (SDBS) i didodecildimetil amonijevoga bromida (DDAB) u vodi te u vodenim otopinama neionskoga dvolančanog PAT, 4-(l-pentilheptil)benzensulfonata (6SDBS). Određivanje faznoga dijagrama, područja stvaranja micela i vezikula te faznih prijelaza, određivanje unutarnjih i vanjskih struktura čestica, provedeno je s pomoću metode raspršenja svjetlosti, raspršenja X zraka pod malim kutom te drugih komplementarnih metoda, npr. reoloških mjerenja u pseudo-izotropnim područjima koja dobro indiciraju stvaranje micela i vezikula karakterizirano kritičnim micelizacijskim i vezikularnim koncentracijama. Dodatno, mezofaze su istraživane polarizacijskom i elektronskom mikroskopijom.Surfactant molecules association, growth and aggregation of selt associates into lamellar bilayers (flexible and closed), micelles, vesicles and liquid crystals, is considered to present important fundamental research with application to trans-membrane properties in the drug delivery and encapsulation. Among many practical applications, the amphiphilic aggregates present the possibility of using well defined bilayers and multilayers in the cosmetic and pharmaceutical industry. Associates of catanionic surfactants show a wide variety of particle shapes, sizes and structures, and due to that, the new materials of different properties could be prepared. Vesicles can be formed spontaneously as a result of self-association of flexible monolayers into unilamellar and multilamellar soft particles with closed bilayers. In this paper investigations have been performed in catanionic mixtures of Sodium n-dodecylbenzensulfonate (SDBS) and Didodecyldimetyl ammonium bromide (DDAB) in water, and in the water solutions of nonionic double-chain surfactant, 4-( 1 pentylheptyl)benzenesulfonate (6SDBS). Phase diagram, regions of micelles and vesicles formation, phase transitions, outer and inner structures of particles, were investigated by light scattering, small angle X-ray scattering, and other related methods, e.g., rheological measurements within pseudoisotropic regions that indicated the formation of micelles and vesicles as characterised by the critical micellisation and vesiculation concentrations. In addition, mesophases have been confirmed by polarisation and electron microscopy

Recent Advances in Catanionic Mixtures

Most surfactant mixtures display synergistic physicochemical properties, which have led to their extensive application in various technologies. Aqueous mixtures of two oppositely charged surfactants, so‐called catanionic surfactant mixtures, exhibit the strongest synergistic effect, which is manifested as high surface activity, enhanced adsorption and a low critical aggregation concentration. In addition, catanionic systems display rich phase behavior and a range of nano and microstructures, including small spherical micelles, rod‐like micelles as well as open and closed bilayers (vesicles). The spontaneous formation of catanionic vesicles is of special interest due to their various applications in nanotechnology and pharmaceutical formulations. In this chapter, the properties of catanionic mixtures of amphiphilic molecules with advantageous properties are discussed. Since numerous papers dealing with catanionic mixtures of monomeric surfactants already exist, the aim of this chapter is to summarize recent progress in mixtures of structurally different surfactants. At the end of the chapter, special emphasis is placed on applications of catanionic mixtures

Kustosi u akciji: revizija i digitalizacija roda Fritillaria L. (Liliaceae) u herbarijskim zbirkama ZA, ZAHO, CNHM i ZAGR

A total of 289 herbarium sheets with 803 specimens from the genus Fritillaria within ZA, ZAHO, CNHM and ZAGR collections were digitized. Altogether 23 taxa were registered within studied collections. The exsiccata originate from 20, mostly European countries; however 72% are from Croatia. The revision of the herbarium sheets collected in Croatia resulted with five native taxa and their historical distributional data for the country. The average age of the collected specimens was 85 years. Based on our herbaria revision, the area of distribution of F. messanensis ssp. gracilis greatly increased.Digitalizacijom roda Fritillaria (kockavica) u herbarijskim zbirkama ZA, ZAHO, CNHM i ZAGR obuhvaćeno je ukupno 289 herbarijskih listova s 803 jedinke. Zabilježene su ukupno 23 svojte. Eksikati potječu iz 20 uglavnom europskih država, od čega 72 % iz Hrvatske. Revizijom herbarijskih listova sakupljenih na području Hrvatske zabilježeno je pet autohtonih svojti kockavica te su dobiveni povijesni podaci o njihovoj rasprostranjenosti. Prosječna starost herbarijskih primjeraka je 85 godina. Revizijom herbarijskih primjeraka areal svojte F. messanensis ssp. gracilis je značajno povećan

Novi podaci o rijetkoj endemičnoj vrsti Grafia golaka (Hacq.) Rchb. (Apiaceae) u Hrvatskoj

The last record of Grafia golaka, a very rare relict umbellifer of disjunct Apennine-Dinaric distribution was latest reported from Croatia back in 1904. During our survey, this endemic was found on seven new localities in Gorski Kotar, in altitudinal range between 1273 and 1421 m a.s.l. It was recorded in altimontan-subalpine altitudinal belt within beech forest, in forest clearings and along forest fringes, in dwarf willow shrub as well as within the sinkhole vegetation.Vrlo rijetka reliktna vrsta štitarke Grafia golaka, koja ima disjunktnu apeninsko-dinarsku rasprostranjenost, posljednji je put u Hrvatskoj zabilježena 1904. godine. Tijekom našeg istraživanja ovu endemičnu vrstu pronašli smo na sedam novih lokaliteta u Gorskom kotaru, u visinskom rasponu između 1273 i 1421 m n.m. Vrsta je zabilježena u pretplaninskom visinskom pojasu, unutar bukove šume, na šumskim čistinama, uzduž rubova šuma, u niskim vrbicima te u vegetaciji ponikvi

Atomic force microscopy reveals new biophysical markers for monitoring subcellular changes in oxidative injury: Neuroprotective effects of quercetin at the nanoscale

Oxidative stress has been recognised as an important pathological mechanism underlying the development of neurodegenerative diseases. The biomarkers for assessing the degree of oxidative stress have been attracting much interest because of their potential clinical relevance in understanding the cellular effects of free radicals and evaluation of the efficacy of drug treatment. Here, an interdisciplinary approach using atomic force microscopy (AFM) and cellular and biological molecular methods were used to investigate oxidative damage in P19 neurons and to reveal the underlying mechanism of protective action of quercetin. Biological methods demonstrated the oxidative damage of P19 neurons and showed that quercetin improved neuronal survival by preventing H2O2- induced p53 and Bcl-2 down-regulation and modulated Akt and ERK1/2 signalling pathways. For the first time, AFM was employed to evaluate morphologically (roughness, height, Feret dimension) and nanomechanical (elasticity) properties in H2O2-induced neuronal damage. The AFM analysis revealed that quercetin suppressed H2O2-provoked changes in cell membrane elasticity and morphological properties, thus confirming its neuroprotective activity. The obtained results indicate the potential of AFM-measured parameters as a biophysical markers of oxidative stress-induced neurodegeneration. In general, our study suggests that AFM can be used as a highly valuable tool in other biomedical applications aimed at screening and monitoring of drug- induced effects at cellular level