Association of collagen with calcium phosphate promoted osteogenic responses of osteoblast-like MG63 cells

In this investigation, the effects of the association of the collagen (COLL) molecules with the calcium phosphate (CaP) film were examined with respect to both the physicochemical properties of the CaP films and the osteoblast responses, such as the adhesion, proliferation, differentiation, and mineralization. The COLL pre-adsorbed CaP film (CaPA) exhibited significant changes in the surface morphology compared to the COLL incorporated CaP film (CaPC). The adhesions of the osteoblast-like MG63 cells were similar on the CaPC or CaPA films. However, the proliferation of the MG63 cells on CaPC was comparable to CaP but considerably different than CaPA. The differentiation of the MG63 cells was greatly improved on CaPC and CaPA compared to CaP and more pronounced on CaPA. The presence of COLL within or on the CaP films significantly modulated the expression of the phenotypic genes, including osteopontin (OPN), alkaline phosphatase (ALP), and the transforming growth factor-β (TGF-β). The expression patterns of these genes elucidated that COLL that was present within or on the CaP film supported the osteoblast proliferation and differentiation. These positive effects were stronger for CaPA than CaPC. The bone-like nodules formed on all of the specimens. However, the mineralization of CaPC and CaPA was significantly higher than CaP, indicating that the association of CaP with COLL promoted the mineral deposition. Therefore, the association of the COLL molecules with the CaP film induced positive effects on the biomineralization. Overall, the incorporation of COLL efficiently enhanced the osteoblast responses of CaP. This system can be utilized in a drug delivery system using calcium phosphate. Although the incorporation effects were slightly higher for the osteoblast responses of CaPA than CaPC, CaPC can be used when the longer drug release times are desirable.     

Control of surface topography in biomimetic calcium phosphate coatings

The behavior of cells responsible for bone formation, osseointegration, and bone bonding in vivo are governed by both the surface chemistry and topography of scaffold matrices. Bone-like apatite coatings represent a promising method to improve the osteoconductivity and bonding of synthetic scaffold materials to mineralized tissues for regenerative procedures in orthopedics and dentistry. Polycaprolactone (PCL) films were coated with calcium phosphates (CaP) by incubation in simulated body fluid (SBF). We investigated the effect of SBF ion concentration and soaking time on the surface properties of the resulting apatite coatings. CaP coatings were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), and energy dispersive X-ray spectrometry (EDX). Young's modulus (E(s)) was determined by nanoindentation, and surface roughness was assessed by atomic force microscopy (AFM) and mechanical stylus profilometry. CaP such as carbonate-substituted apatite were deposited onto PCL films. SEM and AFM images of the apatite coatings revealed an increase in topographical complexity and surface roughness with increasing ion concentration of SBF solutions. Young's moduli (E(s)) of various CaP coatings were not significantly different, regardless of the CaP phase or surface roughness. Thus, SBF with high ion concentrations may be used to coat synthetic polymers with CaP layers of different surface topography and roughness to improve the osteoconductivity and bone-bonding ability of the scaffold.     

Surface oxide net charge of a titanium alloy: modulation of fibronectin-activated attachment and spreading of osteogenic cells

In the current study, we have altered the surface oxide properties of a Ti6Al4V alloy using heat treatment or radiofrequency glow discharge (RFGD) in order to evaluate the relationship between the physico-chemical and biological properties of the alloy's surface oxide. The effects of surface pretreatments on the attachment of cells from two osteogenic cell lines (MG63 and MC3T3) and a mesenchymal stem cell line (C3H10T1/2) to fibronectin adsorbed to the alloy were measured. Both heat and RFGD pretreatments produced a several-fold increase in the number of cells that attached to fibronectin adsorbed to the alloy at a range of coating concentrations (0.001-10nM FN) for each cell line tested. An antibody (HFN7.1) directed against the central integrin binding domain of fibronectin produced a 65-70% inhibition of cell attachment to fibronectin-coated disks, indicating that cell attachment to the metal discs was dependent on fibronectin binding to cell integrin receptors. Both treatments also accelerated the cell spreading response manifested by extensive flattening and an increase in mean cellular area. The treatment-induced increases in the cell attachment activity of adsorbed fibronectin were correlated with previously demonstrated increases in Ti6Al4V oxide negative net surface charge at physiological pH produced by both heat and RFGD pretreatments. Since neither treatment increased the adsorption mass of fibronectin, these findings suggest that negatively charged surface oxide functional groups in Ti6Al4V can modulate fibronectin's integrin receptor activity by altering the adsorbed protein's conformation. Our results further suggest that negatively charged functional groups in the surface oxide can play a prominent role in the osseointegration of metallic implant materials.     

Effect of honeycomb-patterned surface topography on the adhesion and signal transduction of porcine aortic endothelial cells

Surface topography has vital roles in cellular response. Here, to investigate the mechanism behind cellular response to surface topography, we prepared honeycomb (HC)-patterned films from poly(epsilon-caprolactone) (PCL) with micropatterned surface topography by casting a polymer solution of water-immiscible solvent under high humidity. We characterized the adsorption of fibronectin (Fn) on the film using atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). The response of porcine aortic endothelial cells (PAECs) to adsorbed Fn molecules onto HC-patterned films was observed by immunofluorescence labeling of vinculin and the actin fiber of PAECs cultured for 1 and 72 h in serum-free medium. The expression of focal adhesion kinase autophosphorylated at the tyrosine residue (pFAK) at 1 h culture was determined using an immunoprecipitation method. Fn adsorbed selectively around the pore edges to form ring-shaped aggregates. The immunostaining results revealed that PAECs adhered to the HC-patterned films at focal contact points localized around pore peripheries. These points correspond to adsorption sites of Fn. The expression of pFAK after 1 h on the HC-patterned film was 3 times higher than that on a corresponding flat film, indicating that the signaling mediated by the binding between Fn and the integrin receptor was more highly activated on the HC-patterned film. These results suggest that the cellular response to HC-patterned films (e.g., adhesion pattern and phosphorylation of FAK) originates from the regularly aligned adsorption pattern of Fn determined by the pore structure of the film.     

Interpretation of protein adsorption: surface-induced conformational changes

Protein adhesion plays a major role in determining the biocompatibility of materials. The first stage of implant integration is the adhesion of protein followed by cell attachment. Surface modification of implants (surface chemistry and topography) to induce and control protein and cell adhesion is currently of great interest. This communication presents data on protein adsorption (bovine serum albumin and fibrinogen) onto model hydrophobic (CH(3)) and hydrophilic (OH) surfaces, investigated using a quartz crystal microbalance (QCM) and grazing angle infrared spectroscopy. Our data suggest that albumin undergoes adsorption via a single step whereas fibrinogen adsorption is a more complex, multistage process. Albumin has a stronger affinity toward the CH(3) compared to OH terminated surface. In contrast, fibrinogen adheres more rapidly to both surfaces, having a slightly higher affinity toward the hydrophobic surface. Conformational assessment of the adsorbed proteins by grazing angle infrared spectroscopy (GA-FTIR) shows that after an initial 1 h incubation few further time-dependent changes are observed. Both proteins exhibited a less organized secondary structure upon adsorption onto a hydrophobic surface than onto a hydrophilic surface, with the effect observed greatest for albumin. This study demonstrates the ability of simple tailor-made monochemical surfaces to influence binding rates and conformation of bound proteins through protein-surface interactions. Current interest in biocompatible materials has focused on surface modifications to induce rapid healing, both of implants and for wound care products. This effect may also be of significance at the next stage of implant integration, as cell adhesion occurs through the surface protein layer.     

Modulation of the functions of osteoblast-like cells on poly(allylamine hydrochloride) and poly(acrylic acid) multilayer films

Deposition of layer-by-layer polyelectrolyte multilayer (PEM) films has been a widely applied surface modification technique to improve the biocompatibility of biomaterials. The objective of this study was to investigate the impact of the deposition of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) multilayer films on adhesion, growth and differentiation of osteoblasts-like MG63 cells. PAH and PAA were deposited sequentially onto tissue culture polystyrene at either pH 2.0 or pH 6.5 with 4-21 layers. While the MG63 cells attached poorly on the PAH/PAA multilayer films deposited at pH 2.0, while the cells adhered to the PEM films deposited at pH 6.5, depending on layer numbers. Cell adhesion, proliferation and osteogenic activities (alkaline phosphatase activity, expression of osteogenic marker genes and mineralization) were highest on the 4-layer PAH/PAA film and decreased with increasing layer numbers. On the other hand, the behavior of MG63 cells did not show any difference on the adjacent even and odd layers, except PEM4 and PEM5, i.e. the surface charges of the PAH/PAA multilayer films with over ten layers seem indifferent to osteoblastic functions. The results in this study suggested that the mechanical properties of PEM films may play a critical role in modulating the behavior of osteoblasts, providing guidance for application of PEM films to osteopaedic implants.     

Development of a biologically relevant calcium phosphate substrate for sum frequency generation vibrational spectroscopy

A novel biologically relevant composite substrate has been prepared consisting of a calcium phosphate (CaP) layer formed by magnetron sputter-coating from a hydroxyapatite (HA) target onto a gold-coated silicon substrate. The CaP layer is intended to mimic tooth and bone surfaces and allows polymers used in oral care to be deposited in a procedure analogous to that used for dental surfaces. The polymer cetyl dimethicone copolyol (CDC) was deposited onto the CaP surface of the substrate by Langmuir Blodgett deposition, and the structure of the adsorbed layer was investigated by the surface specific technique of sum frequency generation (SFG) vibrational spectroscopy. The gold sublayer provides enhancement of the SFG signal arising from the polymer but plays no part in the adsorption of the polymer. The surface morphology of the substrate was investigated using SEM and AFM. The surface roughness was commensurate with that of the thermally evaporated gold sublayer and uniform over areas of at least 36 mum(2). The chemical composition of the CaP-coated surface was determined by FTIR and TOF-SIMS. It was concluded that the surface is primarily calcium phosphate present as a mixture of amorphous, non-hydroxylated phases rather than solely stoichiometric hydroxyapatite. The SFG spectra from CDC on CaP were closely similar, both in resonance wavenumbers and in their relative intensities, with spectra of thin films of CDC recorded directly on gold. Application of previous analysis of the spectra of CDC on gold therefore enabled interpretation of the polymer orientation and conformation on the CaP substrate.     

Spatially controlled cell adhesion via micropatterned surface modification of poly(dimethylsiloxane)

Spatial control of cell growth on surfaces can be achieved by the selective deposition of molecules that influence cell adhesion. The fabrication of such substrates often relies upon photolithography and requires complex surface chemistry to anchor adhesive and inhibitory molecules. The production of simple, cost-effective substrates for cell patterning would benefit numerous areas of bioanalytical research including tissue engineering and biosensor development. Poly(dimethylsiloxane) (PDMS) is routinely used as a biomedical implant material and as a substrate for microfluidic device fabrication; however, the low surface energy and hydrophobic nature of PDMS inhibits its bioactivity. We present a method for the surface modification of PDMS to promote localized cell adhesion and proliferation. Thin metal films are deposited onto PDMS through a physical mask in the presence of a gaseous plasma. This treatment generates topographical and chemical modifications of the polymer surface. Removal of the deposited metal exposes roughened PDMS regions enriched with hydrophilic oxygen-containing species. The morphology and chemical composition of the patterned substrates were assessed by optical and atomic force microscopies as well as X-ray photoelectron spectroscopy. We observed a direct correlation between the surface modification of PDMS and the micropatterned adhesion of fibroblast cells. This simple protocol generates inexpensive, single-component substrates capable of directing cell attachment and growth.     

AFM analysis of organic silane thin films for bioMEMS applications

Designing surfaces that elicit the desirable response is essential for bioMEMS (biological microelectromechanical systems) applications. To this end, we have developed two different types of silane film—hydrophobic and hydrophilic—using vinyltrichlorosilane and poly(ethylene glycol) silane, respectively. As the surface topography plays a very important role in governing protein or cell interactions, these films were characterized extensively using atomic force microscopy. All the films developed were found to have a very low root‐mean‐square roughness value (<1.3 nm). Furthermore, the topography of protein‐adsorbed silane‐modified surfaces was investigated because cell adhesion is mediated primarily by proteins. Three‐dimensional and section plots were able to differentiate the way in which protein interacts with hydrophobic and hydrophilic surfaces. Copyright © 2003 John Wiley & Sons, Ltd.     

Kinetics of conformational changes of fibronectin adsorbed onto model surfaces

Fibronectin (FN), a large glycoprotein found in body fluids and in the extracellular matrix, plays a key role in numerous cellular behaviours. We investigate FN adsorption onto hydrophilic bare silica and hydrophobic polystyrene (PS) surfaces using Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) in aqueous medium. Adsorption kinetics using different bulk concentrations of FN were followed for 2h and the surface density of adsorbed FN and its time-dependent conformational changes were determined. When adsorption occurs onto the hydrophilic surface, FN molecules keep their native conformation independent of the adsorption conditions, but the amount of adsorbed FN increases with time and the bulk concentration. Although the protein surface density is the same on the hydrophobic PS surface, this has a strong impact on the average conformation of the adsorbed FN layer. Indeed, interfacial hydration changes induced by adsorption onto the hydrophobic surface lead to a decrease in unhydrated beta-sheet content and cause an increase in hydrated beta-strand and hydrated random domain content of adsorbed FN. This conformational change is mainly dependent on the bulk concentration. Indeed, at low bulk concentrations, the secondary structures of adsorbed FN molecules undergo strong unfolding, allowing an extended and hydrated conformation of the protein. At high bulk concentrations, the molecular packing reduces the unfolding of the stereoregular structures of the FN molecules, preventing stronger spreading of the protein.     

Immobilized hyperbranched glycoacrylate films as bioactive supports

[Image: see text] We report on the low-pressure plasma immobilization, characterization and application of thin films of hyperbranched glycoacrylates, poly(3-O-acryloyl-alpha,beta-D-glucopyranoside) (AGlc), on PTFE-like fluorocarbon surfaces. This method is an efficient and versatile way to immobilize sugar-carrying branched acrylates as thin films of approximately 5 nm thickness on polymeric substrates while the functional groups and properties of the immobilized molecules are largely retained. The extent of poly(AGlc) degradation during plasma immobilization was investigated using FTIR-ATR spectroscopy and XPS. The thickness and topography of the immobilized films were characterized using spectroscopic ellipsometry and SFM, respectively. Studies of protein adsorption, as well as cell adhesion and proliferation on the poly(AGlc) surfaces, showed that these materials are suitable for the control of biointerfacial phenomena. Fluorescence images of fibronectin adsorbed on to the branched glycoacrylate with a mask.     

Surface structure analysis of thin dewetted polymer blend films

The surface structure of thin polymer blend films of deuterated polystyrene (dPS) and polyparamethylstyrene (PpMS) after annealing above the glass transition temperature was investigated. With scanning force microscopy (SFM) the surface topography originated by a dewetting process is detected. The sample surface is covered with small droplets consisting of several polymer molecules. Utilizing grazing incidence small angle neutron scattering (GISANS) the topographical information as well as the in‐plane composition is probed. For thin confined blend films a substructure of the droplets resulting from an additional phase separation process at different length scales is detected.     

AFM imaging of immobilized fibronectin: does the surface conjugation scheme affect the protein orientation/conformation?

Covalent grafting of biomolecules could potentially improve the biocompatibility of materials. However, these molecules have to be grafted in an active conformation to play their biological roles. The present work aims at verifying if the surface conjugation scheme of fibronectin (FN) affects the protein orientation/conformation and activity. FN was grafted onto plasma-treated fused silica using two different crosslinkers, glutaric anhydride (GA) or sulfosuccinimidyl 4-(p-maleimidophenyl)butyrate (SMPB). Fused silica was chosen as a model surface material because it presents a roughness well below the dimensions of FN, therefore allowing AFM analyses with appropriate depth resolution. Cell adhesion assays were performed to evaluate the bioactivity of grafted FN. Cell adhesion was found to be higher on GA-FN than on SMPB-FN. Since FN-radiolabeling assays allowed us to rule out a surface concentration effect (approximately 80 ng/cm2 of FN on both crosslinkers), it was hypothesized that FN adopted a more active conformation when grafted via GA. In this context, the FN conformation on both crosslinkers was investigated through AFM and contact angle analyses. Before FN grafting, GA- and SMPB-modified surfaces had a similar water contact angle, topography, and roughness. However, water contact angles of GA-FN and SMPB-FN surfaces clearly show differences in surface hydrophilicity, therefore indicating a dependence of protein organization toward the conjugation strategy. Furthermore, AFM results demonstrated that surface topography and roughness of both FN-conjugated surfaces were significantly different. Distribution analysis of FN height and diameter confirmed this observation as the protein dimensions were significantly larger on GA than SMPB. This study confirmed that the covalent immobilization scheme of biomolecules influences their conformation and, hence, their activity. Consequently, selecting the appropriate conjugation strategy is of paramount importance in retaining molecule bioactivity.     

Optical and surface characterization of amorphous boron nitride thin films for use as blood compatible coatings

The aim of this work is the investigation of the haemocompatibility properties of homogeneous and amorphous boron nitride (a-BN) thin films, through the adsorption of two basic blood plasma proteins, human serum albumin (HSA) and fibrinogen (Fib). The a-BN thin films were grown onto c-Si(100) substrates under different values of substrate bias voltage, employing the radio frequency (RF) magnetron sputtering technique. For the consideration of the optical, compositional and structural properties of the films, Spectroscopic Ellipsometry (SE) in the Vis–UV spectral region was used, while for the study of surface topography and surface charge distribution as well as of the wetting properties of the a-BN thin films, Atomic Force Microscopy (AFM), Electric Force Microscopy (EFM) and Contact Angle measurements were additionally employed. The properties of the thin films were correlated with their haemocompatibility, through the estimation of the ratio of HSA/Fib surface concentration. The sp³ content of the samples does not seem to correlate with the haemocompatibility of the a-BN thin films. However, the surface properties determine the thrombogenicity potential of the studied samples. More precisely, the a-BN films with a less negatively charged surface exhibit the smallest possibility of clot formation, possibly due to the interactions between the charged chains of the Fib molecules and the a-BN surface, while slight changes in the surface roughness do not affect their haemocompatibility properties. The wetting properties determine the thickness of the adsorbed Fib as well as the ratio of HSA/Fib surface concentration.     

Nanoscale topography reduces fibroblast growth, focal adhesion size and migration-related gene expression on platinum surfaces

Controlling cellular responses on biomaterial surfaces is crucial in biomedical applications such as tissue engineering and implantable prosthetics. Since cells encounter various nanoscale topographic features in their natural environment, it has been postulated that surface nanotopography may be an alternative route to fabricate biomaterials with a desirable cellular response. In this framework, we investigated the responses of primary human fibroblasts to platinum substrates with different levels of surface roughness at the nanoscale. The nanorough surfaces were fabricated by using the glancing angle deposition technique (GLAD). We found that levels of cellular responses depended on the surface roughness and the size of the nanoscale features. We showed that in response to nanotopography cells spread less and have an elongated morphology, displaying signs of actin cytoskeleton impairment and reduced formation of focal adhesion complexes. Although cell growth and adhesion were impaired on the nanorough substrates, cell viability was not affected by topography. To a minor extent our results also indicate that cell migration might be reduced on the nanorough surfaces, since a significantly lower gene expression of migration related genes were found on the roughest surfaces as compared to the flat reference. The results presented here demonstrate that surface nanotopography influences fibroblasts responses on platinum, which may be used to reduce cellular adhesion on platinum implant surfaces such as implantable neural electrodes.     

Hydrophobic and electrostatic interactions in the adsorption of fibronectin at maleic acid copolymer films

Adsorption and desorption of fibronectin (FN) were investigated at thin films of alternating maleic acid copolymers with octadecene (POMA) and with propene (PPMA). The hydrophobicity and charge density of the polymers were modulated by the choice of the comonomer. In consequence, the dominant forces between the substrate and the protein were specified as hydrophobic interaction for POMA and electrostatic interaction for PPMA. The adsorption kinetics were investigated in situ as variations of the optical thickness, adsorbed mass, and viscoelastic properties (detected by reflectometric interference spectroscopy and quartz crystal microbalance technique, respectively) while alterations of the electrosurface properties were derived from surface conductivity data and isoelectric points (by streaming potential/current measurements using a microslit electrokinetic setup). The results demonstrate that the interfacial mode of adsorbed FN depends on the predominant interactions: large amounts of FN were tightly bound to POMA by hydrophobic interactions. In contrast, FN adsorbed on PPMA was concluded to attain an unfolded structure allowing for the "electrostatic matching" of positively charged residues on FN with the maleic acid groups. This conclusion was supported by the acidic IEP of 3.2 found for FN on PPMA and a significant reduction of the surface conductivity of the FN-covered polymer film, whereas FN on POMA showed an IEP of 4.2 (close to the intrinsic IEP of FN), indicating a stochastic orientation of the adsorbed protein.     

Structural and topographical characteristics of adsorbed WPI and monoglyceride mixed monolayers at the air-water interface

In this work we have analyzed the structural and topographical characteristics of mixed monolayers formed by an adsorbed whey protein isolate (WPI) and a spread monoglyceride monolayer (monopalmitin or monoolein) on the previously adsorbed protein film. Measurements of the surface pressure (pi)-area (A) isotherm were obtained at 20 degrees C and at pH 7 for protein-adsorbed films from water in a Wilhelmy-type film balance. Since the surface concentration (1/A) is actually unknown for the adsorbed monolayer, the values were derived by assuming that the A values for adsorbed and spread monolayers were equal at the collapse point of the mixed film. The pi-A isotherm deduced for adsorbed WPI monolayer in this work is practically the same as that obtained directly by spreading. For WPI-monoglyceride mixed films, the pi-A isotherms for adsorbed and spread monolayers at pi higher than the equilibrium surface pressure of WPI are practically coincident, a phenomenon which may be attributed to the protein displacement by the monoglyceride from the interface. At lower surface pressures, WPI and monoglyceride coexist at the interface and the adsorbed and spread pi-A isotherms (i.e., the monolayer structure of the mixed films) are different. Monopalmitin has a higher capacity than monoolein for the displacement of protein from the air-water interface. However, some degree of interactions exists between proteins and monoglycerides and these interactions are higher for adsorbed than for spread films. The topography of the monolayer corroborates these conclusions.     

Topography-induced cell adhesion to Acr-sP(EO-stat-PO) hydrogels: the role of protein adsorption

Topographic surface patterning of intrinsically non-adhesive P(EO-stat-PO)-based hydrogels can lead to the adhesion and spreading of fibroblasts. Explanations for this unexpected behavior are discussed, particularly with regard to non-specific protein adsorption from the serum-supplemented culture medium. The presence of serum proteins is shown to be essential for adhesion. Adsorption of plasma and ECM proteins (Fibronectin (FN) and Vitronectin (VN)) to the hydrogels is possible. The effect of VN on initial cell adhesion is analyzed in detail. It appears that VN is the main serum component that is crucial for initial cell adhesion to PEG and that surface topography is essential for further, durable adhesion establishment, and spreading.     

Polyelectrolyte multilayers with a tunable Young's modulus: influence of film stiffness on cell adhesion

Mechanical properties of model and natural gels have recently been demonstrated to play an important role in various cellular processes such as adhesion, proliferation, and differentiation, besides events triggered by chemical ligands. Understanding the biomaterial/cell interface is particularly important in many tissue engineering applications and in implant surgery. One of the final goals would be to control cellular processes precisely at the biomaterial surface and to guide tissue regeneration. In this work, we investigate the substrate mechanical effect on cell adhesion for thin polyelectrolyte multilayer (PEM) films, which can be easily deposited on any type of material. The films were cross linked by means of a water-soluble carbodiimide (EDC), and the film elastic modulus was determined using the AFM nanoindentation technique with a colloidal probe. The Young's modulus could be varied over 2 orders of magnitude (from 3 to 400 kPa) for wet poly(L-lysine)/hyaluronan (PLL/HA) films by changing the EDC concentration. The chemical changes upon cross linking were characterized by means of Fourier transform infrared spectroscopy (FTIR). We demonstrated that the adhesion and spreading of human chondrosarcoma cells directly depend on the Young's modulus. These data indicate that, besides the chemical properties of the polyelectrolytes, the substrate mechanics of PEM films is an important parameter influencing cell adhesion and that PEM offer a new way to prepare thin films of tunable mechanical properties with large potential biomedical applications including drug release.     

Peculiarities and mechanism of surface topography changes in photochromic cholesteric oligomer-based films

Detailed investigations of surface topography peculiarities for two cholesteric mixtures with photovariable helix pitch are presented. The mixtures were prepared by doping cholesteric cyclosiloxane with two chiral-photochromic substances possessing different handedness. Both chiral-photochromic dopants are susceptible to UV light-induced E-Z isomerization and changing of their helical twisting power. UV irradiation allows one to change the helix pitch values of the mixtures in a wide spectral range (~350–740 nm). AFM investigation reveals the specific peculiarities of the surface topography of the mixtures’ films (formation of “fingerprint like” topography or circular, spiralized domains depending on helix pitch). Quantitative analysis of the geometry of the domains (size and cross sections) allows one to find the correlations between photo- and thermally induced helix pitch values and surface features of the films. The handedness of the dopants does not affect surface relief topography. A mechanism has been suggested to explain the topographical changes under helix untwisting, which occurs upon slow cooling of mixtures films.