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Bone defect regeneration is one of the great clinical challenges. Suitable bioactive composite scaffolds with high biocompatibility, robust new-bone formation capability and degradability are still required. This work designs and synthesizes an unprecedented bioactive conjugated polymer PT-C 3 -NH 2 , demonstrating low cytotoxicity, cell proliferation/migration-promoting effect, as well as inducing cell differentiation, namely regulating angiogenesis and osteogenesis to MC3T3-E1 cells. PT-C 3 -NH 2 is incorporated into polylactic acid-glycolic acid (PLGA) scaffolds, which is decorated with caffeic acid (CA)-modified gelatin (Gel), aiming to improve the surface water-wettability of PLGA and also facilitate to the linkage of conjugated polymer through catechol chemistry. A 3D composite scaffold PLGA@GC-PT is then generated. This scaffold demonstrates excellent bionic structures with pore size of 50-300 µm and feasible biodegradation ability. Moreover, it also exhibites robust osteogenic effect to promote osteoblast proliferation and differentiation in vitro, thus enabling the rapid regeneration of bone defects in vivo. Overall, this study provides a new bioactive factor and feasible fabrication approach of biomimetic scaffold for bone regeneration., (© 2023 Wiley-VCH GmbH.)

The reaction of amine-terminated polystyrene (PS-NH 2 ) with an epoxy-based dynamic polymer networks (DPNs) above the topology freezing transition temperature of the DPN, results in the disruption of the network by the formation of graft copolymers at the interface between the linear homopolymer and the network. The rate of the disruption decreases with annealing time and is strongly dependent on the molecular weight of the PS-NH 2 , with the lower molecular weight PS-NH 2 reacting much more rapidly than the higher molecular weight PS-NH 2 . A higher catalyst concentration in the DPN also promotes the interfacial reaction, indicating a reaction-rate-controlled process., (© 2021 Wiley-VCH GmbH.)

The rapid proliferation of multidrug-resistant (MDR) bacterial infections has posed the serious health threats. Photodynamic therapy is considered one of the most promising therapeutic strategies for combating bacterial resistance. In the present study, we synthesized an unsymmetrical oligo-p-phenylene ethynylene (OPE), namely OPE3, and investigated its antimicrobial activity against gram-negative and gram-positive MDR bacteria in vitro and in vivo . The results showed that OPE3 had marked antibacterial activity against MDR bacteria under light irradiation conditions. OPE3 exerted a slightly greater effect on gram-positive bacteria than gram-negative bacteria. Biofilm assay results showed that OPE3 could not inhibit biofilm formation at sub-minimum inhibitory concentrations (MICs), whereas a significant decrease in preformed biofilms was observed when they were treated with OPE3 at concentrations ≥2 × MIC. OPE3 had no hemolytic activity or cytotoxicity in mammalian cells at low concentrations. In the mouse model of burn infection caused by Pseudomonas aeruginosa and Staphylococcus aureus , the treatment of infected wounds with OPE3 resulted in a significant dose-dependent reduction in the bacterial load and caused smaller skin lesions. In addition, the levels of the inflammatory cytokines TNF-α and IL-6 in the serum were also significantly reduced. The present study results indicate that OPE3 may serve as a potent antimicrobial molecule for the treatment of MDR bacterial infections.

Stimuli-responsive and active targeted drug release is highly significant and challenging for precise and effective cancer therapy. Herein, a reactive oxygen species (ROS)-responsive drug delivery system iRGD-BDOX@CPNs with active targeting for chemo-/photodynamic (PDT) synergistic therapy has been reported. This nanocarrier iRGD-BDOX@CPNs is constructed by the self-assembly of conjugated polymer poly(fluorene-co-vinylene) (PFV), prodrug BDOX (doxorubicin modified with a phenylboronic acid ester group) and an amphiphilic polymer (DSPE-PEG) modified with internalized RGD (DSPE-PEG-iRGD). The hydrophobic inner cores formed by PFV main chains tightly enclose BDOX. Due to PFV generating many ROS by light triggering, the BDOX prodrug can be in situ activated, resulting in the highly efficient drug release. In addition, the remarkable fluorescence recovery could be used for real-time monitoring of drug delivery and guiding antitumor therapy. Contributing to the specific recognition between iRGD and integrin αvβ3 receptors over-expressed on the surface of tumor cells, the active targeting and uptake of iRGD-BDOX@CPNs in tumor cells are greatly enhanced. The prominent anti-cancer effect of iRGD-BDOX@CPNs is realized by targeted drug delivery and synergistic therapeutic effects of PDT/chemotherapy. This study illustrates that the development of ROS-responsive and targeted drug delivery nanocarriers iRGD-BDOX@CPNs provides a new insight for controllable drug release and tumor precision therapy.

Oxidative damage generated by various biochemical pathways can disrupt the oxidant/antioxidant balance in cells, causing slow wound healing and tissue regeneration; in this regard, a hydrogel dressing with antioxidant properties can promote wound healing; however, its design is still a challenge. Herein, a polydopamine/puerarin (PDA/PUE) nanoparticle-incorporated polyethylene glycol diacrylate hybrid hydrogel (PEG-DA/PDA/PUE) with antioxidant properties was prepared and used as a wound-healing material. Experimental observations indicated that the PEG-DA/PDA/PUE hydrogel possessed excellent swelling capacity and mechanical property. Moreover, the antioxidant capability was enhanced with an increase in the concentration of polydopamine/puerarin nanoparticles in the hydrogel. The hydrogel presented good cell proliferation and antioxidant activity, including a decrease in ROS and increase in the superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity under oxidative stress conditions. Furthermore, the full-thickness skin-defect-regeneration process could be accelerated via the antioxidant hydrogel treatment. This study validated the potential applications of an antioxidant hydrogel for wound healing.

Hydrogels based on natural polymers have bright application prospects in biomedical fields due to their outstanding biocompatibility and biodegradability. However, the poor mechanical performances of pure natural polymer-based hydrogels greatly limit their application prospects. Recently, a variety of strategies has been applied to prepare natural polymer-based hydrogels with enhanced mechanical properties, which generally exhibit stiffening, strengthening, and stretchable behaviors. This article summarizes the recent progress of natural polymer-based hydrogels with enhanced mechanical properties. From a structure point of view, four kinds of hydrogel are reviewed; double network hydrogels, nanocomposite hydrogels, click chemistry-based hydrogels, and supramolecular hydrogels. For each typical hydrogel, its preparation, structure, and mechanical performance are introduced in detail. At the end of this article, the current challenges and future prospects of hydrogels based on natural polymers are discussed and it is pointed out that 3D printing may offer a new platform for the development of natural polymer-based hydrogels., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Multiplex electrochemical sensors for amperometric detection of glutathione disulfide (GSSG), glutathione (GSH), cysteine (Cys), cystine (Cyss), β-nicotinamide adenine dinucleotide phosphate (NADP + ) and coenzyme II reduced tetrasodium salt (NADPH) were developed, in which analysis of Cyss, NADP + and NADPH are the first report using this sensing system. Specificity of these sensors were ensured by a layer of molecularly imprinted polymer (MIP) which was electropolymerized in situ with the analytes as template. All the sensors were tested with standard buffers and mouse blood samples, showing satisfactory performance towards the corresponding analytes. Dynamic concentration for the six analytes was in the range of 10 -11 -10 -8 mol/L with the detection limit down to 20 pmol/L. In addition, artificially synthesized MIP film on the electrodes allowed for good selectivity and stability. Real blood sample measurement proved that the sensors owned decent accuracy with recovery value ranging from 92%~112%. More importantly, blood samples from lung cancer patients and healthy donors were assayed by using the proposed sensors. Redox potentials (Ehc) were calculated based on the contents of these endogenic substances, which were utilized to reflect the health status of human body and help diagnose lung cancer. The levels of GSH, NADPH and the absolute value of Ehc (GSH/GSSG) in patients with lung cancer are significantly lower (P < 0.01) than those in healthy people, while the contents of GSSG (P < 0.01) are higher. The blood test results suggested that the content of GSH, NADPH, NADP + and Ehc (GSH/GSSG) might serve as biomarkers for lung cancer prediagnosis. These novel sensors for liquid biospy of cancer have cost-benefit and scalability advantage over current techniques, potentially enabling broader clinical access and efficient population screening., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A novel electrochemical sensor has been facilely fabricated by applying composite elements consisting of nitrogen and sulfur co-doped activated graphene (N,S-AGR) and molecularly imprinted polymer (MIP). N,S-AGR was synthesized by one-pot pyrogenation of a mixture of thiourea, KOH and graphene oxide, which was introduced to improve electron transfer capability and surface area of the electrode, while the electro-polymerized MIP layer afforded simultaneous recognition and quantification of cyclophosphamide (CPA) by utilizing Fe(CN) 6 3-/4- as probe to indicate electrical signals. Under the optimal conditions, a calibration curve of current shift versus concentration of CPA was got in the range of 8×10 -12 -8×10 -7 molL -1 , and the developed sensor gave a remarkably low detection limit (LOD) of 3.4×10 -12 mol L -1 (S/N=3). Moreover, the as-prepared sensor illustrated other good merits like stability and selectivity, and played a role in real-time therapeutic drug monitoring after CPA administration in rabbit., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The introduction of functional molecules to the surface of magnetic iron oxide nanoparticles (NPs) is of critical importance. Most previously reported methods were focused on surface ligand attachment either by physisorption or covalent conjugation, resulting in limited ligand loading capacity. In this work, we report the seeded growth of a nucleotide coordinated polymer shell, which can be considered as a special form of adsorption by forming a complete shell. Among all of the tested metal ions, Fe(3+) is the most efficient for this seeded growth. A diverse range of guest molecules, including small organic dyes, proteins, DNA, and gold NPs, can be encapsulated in the shell. All of these molecules were loaded at a much higher capacity compared to that on the naked iron oxide NP core, confirming the advantage of the coordination polymer (CP) shell. In addition, the CP shell provides better guest protein stability compared to that of simple physisorption while retaining guest activity as confirmed by the entrapped glucose oxidase assay. Use of this system as a peroxidase nanozyme and glucose biosensor was demonstrated, detecting glucose as low as 1.4 μM with excellent stability. This work describes a new way to functionalize inorganic materials with a biocompatible shell.

Surface-engineered particulate delivery systems for vaccine administration have been widely investigated in experimental and clinical studies. However, little is known about charge-coated microspheres as potential recombinant subunit protein antigen delivery systems in terms of adsorption and related immune responses. In the present study, cationic polymers, including chitosan (CS), chitosan chloride (CSC), and polyethylenimine (PEI), were used to coat PLA microspheres to build positively charged surfaces. Antigen adsorption capacity was enhanced with increased surface charge of coated microspheres. In macrophages, HBsAg adsorbed on the surface of cationic microspheres specifically enhanced antigen uptake and augmented CD86, MHC I, and MHC II expression and IL-1β, IL-6, TNF-α, and IL-12 release. Antigens were more likely to localize independent of lysosomes after phagocytosis in antigen-attached cationic microsphere formulations. After intraperitoneal immunization, cationic microsphere-based vaccine formulations generated a rapid and efficient humoral immune response and cytokine release as compared with aluminum-adsorbed vaccine and free antigens in vivo. Moreover, microspheres coated with cationic polymers with relatively high positive charges and higher antigen adsorption exhibited strong stimulation of the Th1 response. In conclusion, PLA microspheres coated with cationic polymers may be a potential recombinant antigen delivery system to induce strong cell and humoral immune responses.

During its adhesion on external surfaces, a cell exhibits obvious inclination to different molecular chirality, which encourages us to develop a new type of antibacterial material catering to the "chiral taste" of bacteria. On the basis of the natural product borneol (a camphane-type bicyclic monoterpene), a series of borneol-based polymer, polyborneolacrylate (PBA), was successfully prepared and showed superior antibacterial adhesion properties resulting from the borneol isomers on material surface. The results of this study reveal that bacteria simply dislike this type of stubborn surface of PBA, and the PBA surface stereochemistry contributes to the interfacial antibacterial activities. The PBA polymers were evaluated as noncytotoxic and can be simply synthesized, demonstrating their great potential for biomedical applications.

A porous poly(L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) composite scaffold was fabricated using a novel technique comprising powder mixing, compression molding, low-temperature treatment, and particulate leaching without any organic solvent. The effect of this scaffold on osteoblast proliferation and differentiation was evaluated in vitro. The fabricated scaffold had a homogeneously interconnected porous structure with a porosity of 70% and compressive strength of 1.35 MPa. The methylthiazol tetrazolium values and alkaline phosphatase (ALP) activity of osteoblasts seeded on the solvent-free scaffold were significant higher than those of the control. Using real-time PCR, gene expressions of ALP, osteocalcin, and type 1 collagen were shown to be upregulated. As the method does not use any organic solvent, it eliminates problems associated with organic solvent residue and therefore improves the cell compatibility. It has a promising potential for the preparation of porous scaffold for bone tissue engineering.

Multihollow poly(methyl methacrylate) (PMMA) particles were successfully fabricated simply by gamma-ray radiating emulsions consisting of MMA monomers, sulfonated polystyrene (SP) particles, and water. The mechanism on the formation of the holes was studied in detail. It was found that there were two routes to achieve two different multihollow structures dependent on the initial location of SP particles before emulsification. If SP particles first located in the water phase, cage-like hollow PMMA particles were obtained through the formation of a Pickering emulsion. Otherwise, if SP particles first located in the oil (MMA) phase, a different multihollow structure would be produced via the formation of a multiple emulsion. This work provides a simple method to fabricate two different structured multihollow particles using the same conditions.

In this study, a novel heparin-immobilized polyethersulfone (PES) was synthesized. PES was initially sulfonated with chlorosulfonic acid and then 1,6-hexanediamine was grafted to the -SO(3)H groups of sulfonated PES, which subsequently reacted with heparin through a covalent bond by using (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) as catalyst. The hydrophobic/hydrophilic property was characterized by measuring the water contact angle. The data shows decline from 62.29 degrees +/- 1.2 degrees to 47.86 degrees +/- 0.3 degrees for water and 86.79 degrees +/- 0.8 degrees to 68.34 degrees +/- 1.0 degrees for glycerol, which indicates an enhancement of hydrophilicity. Plasma hemolysis assay shows a comparatively low hemolysis ratio of 1.04%, which is below permissible limit of 5%. A higher content of dissociated blood cells and Ca(2+) concentration was found in red blood cell counting and coagulation factor IV test in heparinized PES. Plasma recalcification time of 360 s also offers positive evidence that heparinized PES seems to have a good anticoagulation property. This new heparin-immobilized PES biomaterials may have the potential for biomedical applications., (Copyright 2007 Wiley Periodicals, Inc.)

Abstract: We describe a magnetic nanoparticle drug carrier for controlled drug release that responds to the change in external temperature or pH, with characteristics of longer circulation time and reduced side effects. The novel nanocarrier is characterized by a functionalized magnetite (Fe3O4) core that is conjugated with drug via acid-labile hydrazone-bond and encapsulated by the thermosensitive smart polymer, chitosan-g-poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [chitosan-g-poly(NIPAAm-co-DMAAm)]. The chitosan-g-poly(NIPAAm-co-DMAAm) smart polymer exhibits a lower critical solution temperature (LCST) of ∼38°C, signifying phase transition behavior of the smart polymer and enabling its use for triggering on–off mechanisms. The drug release response was appreciably low at a temperature less than the LCST as compared with a temperature above the LCST. In each case, there was an initial rapid drug release, followed by a controlled released in the second stage, especially in a mild acidic buffer solution of pH 5.3. We believe that the drug release occurs via a collapse of the encapsulated thermosensitive polymer and cleavage of the acid-labile hydrazone linkage. [Copyright &y& Elsevier]

Abstract: The objective of the study is to understand the nanoscale near-surface deformation response of two polymer nanocomposite systems with significant differences in ductility during nanoscratching with a Berkovich indenter using a load of 1mN and a scratch velocity of 1μms−1. An accompanying objective is to investigate the commonality in surface deformation behavior between nano- and microscale deformation to reinforce the underlying fundamental principles governing surface deformation. An understanding of surface deformation response is accomplished through determination of physical and mechanical properties, structural characterization and electron microscopy analysis of surface deformation tracks and residual plastically deformed structures. The study suggests for the first time that the understanding derived from microscale surface deformation studies can be extended to nanoscale surface deformation. The microscale response in a polypropylene-based system is characterized by periodic multiple ripple-type deformation tracks that form via a mechanism identical to the periodic single-ripple-type tracks during nanoscale deformation. Similarly, in a less ductile polyethylene-based system, the periodic parabolic tracks and ironing mode of deformation during microscale deformation tend to be significantly reduced in intensity, with ironing being the primary deformation mechanism at the nanoscale. The surface deformation topography suggests that both micro- and nanoscale response is material specific. Additionally, the study suggests that reinforcement of polymers with nanoclay is a viable route to significantly decrease the susceptibility of polymeric materials to micro- and nanoscale deformation and can be discussed in terms of physical and mechanical properties of materials notably percentage crystallinity and elastic recovery. [Copyright &y& Elsevier]

Abstract: We examine here the mechanical behavior and the micromechanism of fracture in impact tested neat and nanoclay-reinforced thermoplastic olefins, both of which have been processed under similar conditions. The reinforcement of thermoplastic olefins with nanoclay increases modulus and yields strength of the resulting nanocomposite and retains impact strength. The enhancement of modulus and yield strength is related to the reinforcement effect of nanoclay, while the retention of impact strength on reinforcement is attributed to the strong interaction between clay and polymer matrix. Both neat and clay-reinforced thermoplastic olefins are characterized by plastic deformation processes that involve ductile ploughing, fibrillation and voiding. [Copyright &y& Elsevier]

Abstract: The reinforcement of polyethylene and polypropylene with 4wt.% nanoclay exhibits a striking variation in impact toughness behavior in the temperature range of −40 to +70°C under identical processing conditions. The reinforcement of polypropylene with nanoclay increases the impact strength, while polyethylene experiences a decrease in the impact strength. To explain this dissimilar and contrasting behavior, we discuss here the possibility of clay–polymer interaction based on conclusions derived from differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), and Fourier transform infrared spectroscopy (FTIR). The observations suggest the possibility of a strong polypropylene–clay interaction, whereas the polyethylene–clay interaction is weak. The strong interaction in polypropylene–clay system is responsible for significant change in physical and mechanical properties. [Copyright &y& Elsevier]

Polymer nanocomposites, or more appropriately polymer nanostructured materials, represent a radical alternative to the conventional filled polymers and polymer blends, in which discrete constituents on the order of a few nanometres are incorporated in the polymer matrix. In the last decade, the utility of inorganic nanoparticles as additives to enhance polymer performance has been established and now provides numerous commercial opportunities, ranging from advanced aerospace systems to commodity plastics. The incorporation of low volume additions (1–5 wt-%) of highly anisotropic nanoparticles, such as layered silicates or carbon nanotubes, have resulted in property enhancements with respect to the neat polymer that are comparable with that achieved by conventional loadings (15–40 wt-%) of traditional fillers. The lower loadings facilitate processing and reduce component weight. In addition, unique value added properties not normally possible with traditional fillers were also observed, such as high stiffness, reduced permeability, optical clarity and electrical conductivity have been achieved. However, the development of chemical and processing procedures to disrupt the low-dimensional crystallites (tactoids and ropes) to achieve uniform distribution of the nanoelement (layered silicate and single wall carbon nanotube respectively) continues to be a challenge. Even less developed are approaches to provide spatial and orientational control of the hierarchical morphology. There exists an immense potential for polymer nanocomposites, in particular, polypropyelene–clay nanocomposites paving the way for future technologies for the materials community at large. [ABSTRACT FROM AUTHOR]

Abstract: The micromechanism of plastic deformation during impact loading of polypropylene–clay nanocomposites is examined and compared with the unreinforced polypropylene under identical conditions of processing to underscore the determining role of clay. The addition of clay to polypropylene increases the impact strength in the temperature range of 0 to +70°C. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM) techniques provided an understanding of the micromechanism of plastic deformation in terms of the response of the polymer matrix, nucleating capability of the reinforcement, crystal structure, percentage crystallinity, lamellae thickness, and particle–matrix interface. The enhancement of toughness on reinforcement of polypropylene with nanoclay is associated with change in the primary mechanism of plastic deformation from crazing and vein-type in neat polypropylene to microvoid-coalescence-fibrillation process in the nanocomposite. [Copyright &y& Elsevier]

Abstract: The mechanical response of clay–reinforced polyethylene nanocomposite is investigated and the behavior compared with the un-reinforced polyethylene under identical conditions of processing. The micromechanism of plastic deformation during impact loading of neat polyethylene and clay–reinforced polyethylene nanocomposite are studied with scanning electron microscopy (SEM). The impact strength of composites is linked to structural studies by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM) and SEM observations. The addition of clay to polyethylene retains adequately high-impact strength in the investigated temperature range of −40 to +70°C. The micromechanism of deformation is altered from a combination of craze and drawing of fibrils in neat polyethylene to microvoid coalescence-fibrillated process in the nanocomposite. The aspects related to micromechanism of deformation are discussed. [Copyright &y& Elsevier]

Abstract: The study describes the surface deformation behavior and susceptibility to surface damage in two clay-reinforced intercalated polymer nanocomposite systems that have significant differences in ductility. Neat polybutene (PB) experiences a severe and distinct ‘quasi-periodic psiloma-type’ deformation process that was absent on reinforcement with clay. In clay-PB nanocomposite system, ‘ironing,’ a less severe surface damage mechanism is dominant. While in the less ductile polymethylpentene (PMP) polymer system, ploughing–tearing and micro-voiding constitute the surface deformation mechanism. Both the clay-reinforced polymer nanocomposite systems experience significantly reduced stress whitening and is characterized by a lower change in gray level. The optical transparency of the polymeric systems is governed by the micromechanism of deformation and is greater for the ductile PB system. The difference in the susceptibility to surface deformation behavior is discussed in terms of mechanical properties and clay-induced structural changes. The reinforcement of polymers with nanoclay has a positive overriding positive influence on the modulus and yield strength that increases the resistance to surface deformation. [Copyright &y& Elsevier]

The electrical resistivity of a thermoresponsive polyurethane shape-memory polymer (SMP) filled with micron sized Ni powders is investigated in this letter. We show that, by forming conductive Ni chains under a weak static magnetic field (0.03 T), the electrical conductivity of the SMP composite in the chain direction can be improved significantly, which makes it more suitable for Joule heat induced shape recovery. In addition, Ni chains reinforce the SMP significantly but their influence on the glass transition temperature is about the same as that of the randomly distributed Ni powders. [ABSTRACT FROM AUTHOR]

Abstract: The dispersion of small weight fraction of carbon nanotube (CNT) in Nylon 6,6 introduces a significant difference in the structure and phase evolution during crystallization at ambient and elevated pressures. In the nanocomposite, the γ-phase is promoted at low crystallization pressure of ∼0.1–25MPa and is in striking contrast to pure Nylon 6,6, where γ-phase is nucleated only at crystallization pressures exceeding ∼50MPa. The differences in the behavior of Nylon 6,6 and its nanocomposites is attributed to CNT–polymer interface driven nucleation, which is also responsible for significant reduction in spherulite size and increase in crystallinity. The nanoindentation behavior of the nanocomposite is assessed via nanoscale deformation experiments, which indicated that a significantly higher indentation-force is required for the Nylon 6,6–CNT nanocomposite as compared to Nylon 6,6 to produce a constant displacement. The observed significantly higher modulus and hardness is primarily CNT-induced effect. This observation is of particular relevance to functional devices because they are most likely to experience force in the nanonewton range, which can induce deformation at the micro- and/or nanometer scale. [Copyright &y& Elsevier]

Abstract: The near surface deformation during scratching of neat polypropylene (PP) and polymer nanocomposites (PP–clay) at loads of 0.2–6kgf is described in terms of characteristics of scratch morphology and scratch deformation parameters. In neat PP, the application of higher loads introduces severe ironing deformation, disrupting the periodic parabolic nature of scratch tracks such that the material plastically flows along the ironing zone. Under identical test conditions, the severity of surface deformation in PP–clay nanocomposites, which leads to stress whitening is significantly reduced. At lower loads, the periodic nature of tracks is retained together with ironing, while at higher loads, ploughing occurred. The resistance to scratch deformation is discussed in terms of modulus, elastic recovery, and scratch hardness. [Copyright &y& Elsevier]