Fluorescent Nanocarbons: From Synthesis and Structure to Cancer Imaging and Therapy

Nanocarbons are emerging at the forefront of nanoscience, with diverse carbon nanoforms emerging over the past two decades. Early cancer diagnosis and therapy, driven by advanced chemistry techniques, play a pivotal role in mitigating mortality rates associated with cancer. Nanocarbons, with an attractive combination of well-defined architectures, biocompatibility, and nanoscale dimension, offer an incredibly versatile platform for cancer imaging and therapy. This paper aims to review the underlying principles regarding the controllable synthesis, fluorescence origins, cellular toxicity, and surface functionalization routes of several classes of nanocarbons: carbon nanodots, nanodiamonds, carbon nanoonions, and carbon nanohorns. This review also highlights recent breakthroughs regarding the green synthesis of different nanocarbons from renewable sources. It also presents a comprehensive and unified overview of the latest cancer-related applications of nanocarbons and how they can be designed to interface with biological systems and work as cancer diagnostics and therapeutic tools. The commercial status for large-scale manufacturing of nanocarbons is also presented. Finally, it proposes future research opportunities aimed at engendering modifiable and high-performance nanocarbons for emerging applications across medical industries. This work is envisioned as a cornerstone to guide interdisciplinary teams in crafting fluorescent nanocarbons with tailored attributes that can revolutionize cancer diagnostics and therapy.

Engineered Sustainable Omniphobic Coatings to Control Liquid Spreading on Food-Contact Materials

The adhesion of sticky liquid foods to a contacting surface can cause many technical challenges. The food manufacturing sector is confronted with many critical issues that can be overcome with long-lasting and highly nonwettable coatings. Nanoengineered biomimetic surfaces with distinct wettability and tunable interfaces have elicited increasing interest for their potential use in addressing a broad variety of scientific and technological applications, such as antifogging, anti-icing, antifouling, antiadhesion, and anticorrosion. Although a large number of nature-inspired surfaces have emerged, food-safe nonwetted surfaces are still in their infancy, and numerous structural design aspects remain unexplored. This Review summarizes the latest scientific research regarding the key principles, fabrication methods, and applications of three important categories of nonwettable surfaces: superhydrophobic, liquid-infused slippery, and re-entrant structured surfaces. The Review is particularly focused on new insights into the antiwetting mechanisms of these nanopatterned structures and discovering efficient platform methodologies to guide their rational design when in contact with food materials. A detailed description of the current opportunities, challenges, and future scale-up possibilities of these nanoengineered surfaces in the food industry is also provided.

Impact of multiscale surface topography characteristics on Candida albicans biofilm formation: From cell repellence to fungicidal activity

While there has been significant research conducted on bacterial colonization on implant materials, with a focus on developing surface modifications to prevent the formation of bacterial biofilms, the study of Candida albicans biofilms on implantable materials is still in its infancy, despite its growing relevance in implant-associated infections. C. albicans fungal infections represent a significant clinical concern due to their severity and associated high fatality rate. Pathogenic yeasts account for an increasing proportion of implant-associated infections, since Candida spp. readily form biofilms on medical and dental device surfaces. In addition, these biofilms are highly antifungal-resistant, making it crucial to explore alternative solutions for the prevention of Candida implant-associated infections. One promising approach is to modify the surface properties of the implant, such as the wettability and topography of these substrata, to prevent the initial Candida attachment to the surface. This review summarizes recent research on the effects of surface wettability, roughness, and architecture on Candida spp. attachment to implantable materials. The nanofabrication of material surfaces are highlighted as a potential method for the prevention of Candida spp. attachment and biofilm formation on medical implant materials. Understanding the mechanisms by which Candida spp. attach to surfaces will allow such surfaces to be designed such that the incidence and severity of Candida infections in patients can be significantly reduced. Most importantly, this approach could also substantially reduce the need to use antifungals for the prevention and treatment of these infections, thereby playing a crucial role in minimizing the possibility contributing to instances of antimicrobial resistance. STATEMENT OF SIGNIFICANCE: In this review we provide a systematic analysis of the role that surface characteristics, such as wettability, roughness, topography and architecture, play on the extent of C. albicans cells attachment that will occur on biomaterial surfaces. We show that exploiting bioinspired surfaces could significantly contribute to the prevention of antimicrobial resistance to antifungal and chemical-based preventive measures. By reducing the attachment and growth of C. albicans cells using surface structure approaches, we can decrease the need for antifungals, which are conventionally used to treat such infections.

Genetic Transformation of Plasmid DNA into Escherichia coli Using High Frequency Electromagnetic Energy

We present a novel technique of genetic transformation of bacterial cells mediated by high frequency electromagnetic energy (HF EME). Plasmid DNA, pGLO (5.4 kb), was successfully transformed into Escherichia coli JM109 cells after exposure to 18 GHz irradiation at a power density between 5.6 and 30 kW m-2 for 180 s at temperatures ranging from 30 to 40 °C. Transformed bacteria were identified by the expression of green fluorescent protein (GFP) using confocal scanning microscopy (CLSM) and flow cytometry (FC). Approximately 90.7% of HF EME treated viable E. coli cells exhibited uptake of the pGLO plasmid. The interaction of plasmid DNA with bacteria leading to transformation was confirmed by using cryogenic transmission electron microscopy (cryo-TEM). HF EME-induced plasmid DNA transformation was shown to be unique, highly efficient, and cost-effective. HF EME-induced genetic transformation is performed under physiologically friendly conditions in contrast to existing techniques that generate higher temperatures, leading to altered cellular integrity. This technique allows safe delivery of genetic material into bacterial cells, thus providing excellent prospects for applications in microbiome therapeutics and synthetic biology.

Piercing of the Human Parainfluenza Virus by Nanostructured Surfaces

This paper presents a comprehensive experimental and theoretical investigation into the antiviral properties of nanostructured surfaces and explains the underlying virucidal mechanism. We used reactive ion etching to fabricate silicon (Si) surfaces featuring an array of sharp nanospikes with an approximate tip diameter of 2 nm and a height of 290 nm. The nanospike surfaces exhibited a 1.5 log reduction in infectivity of human parainfluenza virus type 3 (hPIV-3) after 6 h, a substantially enhanced efficiency, compared to that of smooth Si. Theoretical modeling of the virus-nanospike interactions determined the virucidal action of the nanostructured substrata to be associated with the ability of the sharp nanofeatures to effectively penetrate the viral envelope, resulting in the loss of viral infectivity. Our research highlights the significance of the potential application of nanostructured surfaces in combating the spread of viruses and bacteria. Notably, our study provides valuable insights into the design and optimization of antiviral surfaces with a particular emphasis on the crucial role played by sharp nanofeatures in maximizing their effectiveness.

Turning food waste into value-added carbon dots for sustainable food packaging application: A review

Carbon dots (CDs) are a recent addition to the nanocarbon family, encompassing both crystalline and amorphous phases. They have sparked significant research interest due to their unique electrical and optical properties, remarkable biocompatibility, outstanding mechanical characteristics, customizable surface chemistry, and negligible cytotoxicity. Their current applications are mainly limited to flexible photonic and biomedical devices, but they have also garnered attention for their potential use in intelligent packaging. The conversion of food waste into CDs further contributes to the concept of the circular economy. It provides a comprehensive overview of emerging green technologies, energy-saving reactions, and cost-effective starting materials involved in the synthesis of CDs. It also highlights the unique properties of biomass-derived CDs, focusing on their structural performance, cellular toxicity, and functional characteristics. The application of CDs in the food industry, including food packaging, is summarized in a concise manner. This paper sheds light on the current challenges and prospects of utilizing CDs in the packaging industry. It aims to provide researchers with a roadmap to tailor the properties of CDs to suit specific applications in the food industry, particularly in food packaging.

Translocation and fate of nanospheres in pheochromocytoma cells following exposure to synchrotron-sourced terahertz radiation

The routes by which foreign objects enter cells is well studied; however, their fate following uptake has not been explored extensively. Following exposure to synchrotron-sourced (SS) terahertz (THz) radiation, reversible membrane permeability has been demonstrated in eukaryotic cells by the uptake of nanospheres; nonetheless, cellular localization of the nanospheres remained unclear. This study utilized silica core-shell gold nanospheres (AuSi NS) of diameter 50 ± 5 nm to investigate the fate of nanospheres inside pheochromocytoma (PC 12) cells following SS THz exposure. Fluorescence microscopy was used to confirm nanosphere internalization following 10 min of SS THz exposure in the range 0.5-20 THz. Transmission electron microscopy followed by scanning transmission electron microscopy energy-dispersive spectroscopic (STEM-EDS) analysis was used to confirm the presence of AuSi NS in the cytoplasm or membrane, as single NS or in clusters (22% and 52%, respectively), with the remainder (26%) sequestered in vacuoles. Cellular uptake of NS in response to SS THz radiation could have suitable applications in a vast number of biomedical applications, regenerative medicine, vaccines, cancer therapy, gene and drug delivery.

Structure and Optical Anisotropy of Spider Scales and Silk: The Use of Chromaticity and Azimuth Colors to Optically Characterize Complex Biological Structures

Herein, we give an overview of several less explored structural and optical characterization techniques useful for biomaterials. New insights into the structure of natural fibers such as spider silk can be gained with minimal sample preparation. Electromagnetic radiation (EMR) over a broad range of wavelengths (from X-ray to THz) provides information of the structure of the material at correspondingly different length scales (nm-to-mm). When the sample features, such as the alignment of certain fibers, cannot be characterized optically, polarization analysis of the optical images can provide further information on feature alignment. The 3D complexity of biological samples necessitates that there be feature measurements and characterization over a large range of length scales. We discuss the issue of characterizing complex shapes by analysis of the link between the color and structure of spider scales and silk. For example, it is shown that the green-blue color of a spider scale is dominated by the chitin slab's Fabry-Pérot-type reflectivity rather than the surface nanostructure. The use of a chromaticity plot simplifies complex spectra and enables quantification of the apparent colors. All the experimental data presented herein are used to support the discussion on the structure-color link in the characterization of materials.

Long-term outcomes of different rehabilitation programs in patients with long COVID syndrome: a cohort prospective study

After the resolution of the acute SARS-COV-2 infection, an important percentage of patients do not fully recover and continue to present several symptoms. Nevertheless, there is a lack of data in the literature on the effects of rehabilitation programs on medium- and long-term long COVID symptoms. Therefore, the aim of this study was to evaluate the long-term outcomes after rehabilitation programs in long COVID syndrome patients. A prospective cohort study was conducted from August 2021 to March 2022, involving 113 patients with long COVID syndrome. The patients in the experimental group (EG, n=25) received a tailored and multidisciplinary rehabilitative program, involving aquatic exercises, respiratory and motor exercises, social integration training and neuropsychologic sessions, LASER therapy and magnetotherapy. Patients in the other three comparison groups received eastern medicine techniques (CG1), balneotherapy and physiotherapy (group CG2), self-training and home-based physical exercise (CG3). Once the several rehabilitation protocols had been performed, a structured telephone contact was made with the patients after 6 months ± 7 days from the end of the rehabilitation treatment, in order to record the frequency of hospital ad-missions due to exacerbation of post-exacerbation syndrome, death or disability, and the need for other types of care or drugs. The patients in the comparison groups were more likely to request therapeutic care for emerging long COVID symptoms (χ2=6.635, p=0.001; χ2=13.463, p=0.001; χ2=10.949, p=0.001, respectively), as well as more likely to be hospitalized (χ2=5.357, p=0.021; χ2=0.125, p=0.724; χ2=0.856, p=0.355, respectively) when compared to the patients of the EG. The relative risk (RR) of hospital admissions in the observed cohort was 0.143 ±1,031 (СI: 0.019; 1.078); 0.580±1,194 (CI: 0.056; 6.022); 0,340±1,087 (CI: 0.040; 2.860). The RR of hospital admissions for patients with long COVID syndrome was reduced by 85.7%; 42.0% and 66.0%, respectively, when the experimental rehabilitation technique was employed. In conclusion, a tailored and multidisciplinary rehabilitative program seems to have a better preventive effect not only in the short term, but also over the next 6 months, avoiding the new onset of disabilities and the use of medicines and specialist advice, than other rehabilitative programs. Future studies will need to further investigate these aspects to identify the best rehabilitation therapy, also in terms of cost-effectiveness, for these patients.

Modulation of MG-63 Osteogenic Response on Mechano-Bactericidal Micronanostructured Titanium Surfaces

Despite recent advances in the development of orthopedic devices, implant-related failures that occur as a result of poor osseointegration and nosocomial infection are frequent. In this study, we developed a multiscale titanium (Ti) surface topography that promotes both osteogenic and mechano-bactericidal activity using a simple two-step fabrication approach. The response of MG-63 osteoblast-like cells and antibacterial activity toward Pseudomonas aeruginosa and Staphylococcus aureus bacteria was compared for two distinct micronanoarchitectures of differing surface roughness created by acid etching, using either hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), followed by hydrothermal treatment, henceforth referred to as either MN-HCl or MN-H₂SO₄. The MN-HCl surfaces were characterized by an average surface microroughness (S_a) of 0.8 ± 0.1 μm covered by blade-like nanosheets of 10 ± 2.1 nm thickness, whereas the MN-H₂SO₄ surfaces exhibited a greater S_a value of 5.8 ± 0.6 μm, with a network of nanosheets of 20 ± 2.6 nm thickness. Both micronanostructured surfaces promoted enhanced MG-63 attachment and differentiation; however, cell proliferation was only significantly increased on MN-HCl surfaces. In addition, the MN-HCl surface exhibited increased levels of bactericidal activity, with only 0.6% of the P. aeruginosa cells and approximately 5% S. aureus cells remaining viable after 24 h when compared to control surfaces. Thus, we propose the modulation of surface roughness and architecture on the micro- and nanoscale to achieve efficient manipulation of osteogenic cell response combined with mechanical antibacterial activity. The outcomes of this study provide significant insight into the further development of advanced multifunctional orthopedic implant surfaces.

Surface Characteristics and Bone Biocompatibility of Cold-Sprayed Porous Titanium on Polydimethylsiloxane Substrates

A variant of the cold spray (CS) technique was applied for the functionalization of polymer-based materials such as polydimethylsiloxane (PDMS) to improve the extent of mammalian cell interactions with these substrates. This was demonstrated by the embedment of porous titanium (pTi) into PDMS substrates using a single-step CS technique. CS processing parameters such as gas pressure and temperature were optimized to achieve the mechanical interlocking of pTi in the compressed PDMS to fabricate a unique hierarchical morphology possessing micro-roughness. As evidenced by the preserved porous structure, the pTi particles did not undergo any significant plastic deformation upon impact with the polymer substrate. The thickness of the particle embedment layer was determined, by cross-sectional analysis, ranging from 120 μm to over 200 μm. The behavior of osteoblast-like cells MG63 coming into contact with the pTi-embedded PDMS was examined. The results showed that the pTi-embedded PDMS samples promoted 80-96% of cell adhesion and proliferation during the early stages of incubation. The low cytotoxicity of the pTi-embedded PDMS was confirmed, with cell viability of the MG63 cells being above 90%. Furthermore, the pTi-embedded PDMS facilitated the production of alkaline phosphatase and calcium deposition in the MG63 cells, as demonstrated by the higher amount of alkaline phosphatase (2.6 times) and calcium (10.6 times) on the pTi-embedded PDMS sample fabricated at 250 °C, 3 MPa. Overall, the work demonstrated that the CS process provided flexibility in the parameters used for the production of the modified PDMS substrates and is highly efficient for the fabrication of coated polymer products. The results obtained in this study suggest that a tailorable porous and rough architecture could be achieved that promoted osteoblast function, indicating that the method has promise in the design of titanium-polymer composite materials applied to biomaterials used in musculoskeletal applications.

Plasma for aquaponics

Global environmental, social, and economic challenges call for innovative solutions to food production. Current food production systems require advances beyond traditional paradigms, acknowledging the complexity arising from sustainability and a present lack of awareness about technologies that may help limit, for example, loss of nutrients from soil. Aquaponics, a closed-loop system that combines aquaculture with hydroponics, is a step towards the more efficient management of scarce water, land, and nutrient resources. However, its large-scale use is currently limited by several significant challenges of maintaining desirable water chemistry and pH, managing infections in fish and plants, and increasing productivity efficiently, economically, and sustainably. This paper investigates the opportunities presented by plasma technologies in meeting these challenges, potentially opening new pathways for sustainability in food production.

Magnetic therapy in acute and subacute non-specific back pain: Results of an open multicenter study

Magnetic therapy (MT) is a non-drug method that improves the effectiveness of treatment of musculoskeletal pain, including:acute non-specific back pain (NBP). Objective of our study was to evaluate the results of complex treatment of patients with acute/subacute NBP at home using MT. The study group consisted of 339 patients with severe acute/subacute NBP. All patients received nonsteroidal anti-inflammatory drugs (NSAIDs). 166 patients (Group 1) received a course of MT (ALMAG+ device), 173 patients or a control group (Group 2) who did not receive MT. The dynamics of pain was significantly higher in group 1 than in group 2. So, the intensity of pain during movement (NRS) decreased from 7 [5;8] and 7 [5;8] to 0 [0;13] and 2 [1;3] after 1 month. (p<0.001). Significant differences between Groups 1 and 2 were observed in the dynamics of pain at rest and at night, overall health assessment (OHA), and sleep function and disorders. The average duration of NSAIDs use in Group 1 was 8.8±3.9, Group 2 – 11.8±5.7 days (p<0.001). The use of MT increases the effectiveness of treatment of acute/subacute NBP and reduces the need for NSAIDs use.

Lethal Interactions of Atomically Precise Gold Nanoclusters and Pseudomonas aeruginosa and Staphylococcus aureus Bacterial Cells

Ultrasmall metal nanoclusters (NCs) are employed in an array of diagnostic and therapeutic applications due to their tunable photoluminescence, high biocompatibility, polyvalent effect, ease of modification, and photothermal stability. However, gold nanoclusters' (AuNCs') intrinsically antimicrobial properties remain poorly explored and are not well understood. Here, we share an insight into the antimicrobial action of atomically precise AuNCs based on their ability to passively translocate across the bacterial membrane. Functionalized by a hydrophilic modified-bidentate sulfobetaine zwitterionic molecule (AuNC-ZwBuEt) or a more hydrophobic monodentate-thiolate, mercaptohexanoic acid (AuNC-MHA) molecule, 2 nm AuNCs were lethal to both Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacteria. The bactericidal efficiency was found to be bacterial strain-, time-, and concentration-dependent. The direct visualizations of the translocation of AuNCs and AuNC-cell and subcellular interactions were investigated using cryo-soft X-ray nano-tomography, transmission electron microscopy (TEM), and scanning TEM energy-dispersive spectroscopy analyses. AuNC-MHA were identified in the bacterial cytoplasm within 30 min, without evidence of the loss of membrane integrity. It is proposed that the bactericidal effect of AuNCs is attributed to their size, which allows for efficient energy-independent translocation across the cell membrane. The internalization of both AuNCs caused massive internal damage to the cells, including collapsed subcellular structures and altered cell morphology, leading to the eventual loss of cellular integrity.

Localization of nanospheres in pheochromocytoma-like cells following exposure to high-frequency electromagnetic fields at 18 GHz

Exposure to high-frequency (HF) electromagnetic fields (EMFs) at 18 GHz was previously found to induce reversible cell permeabilization in eukaryotic cells; however, the fate of internalized foreign objects inside the cell remains unclear. Here, silica core-shell gold nanospheres (Au NS) of 20 ± 5 nm diameter were used to study the localization of Au NS in pheochromocytoma (PC 12) cells after exposure to HF EMFs at 18 GHz. Internalization of Au NS was confirmed using fluorescence microscopy and transmission electron microscopy. Analysis based on corresponding scanning transmission electron microscopy energy-dispersive spectroscopy revealed the presence of the Au NS free within the PC 12 cell membrane, cytoplasm, enclosed within intracellular vesicles and sequestered in vacuoles. The results obtained in this work highlight that exposure to HF EMFs could be used as an efficient technique with potential for effective delivery of drugs, genetic material, and nanomaterials into cells for the purpose of cellular manipulation or therapy.

Biodegradation of novel bioplastics made of starch, polyhydroxyurethanes and cellulose nanocrystals in soil environment

Plastic pollution is recognized as a major environmental problem in many countries. Over the last decade, academics have embraced research on bioplastics to discover newer high-end green materials. However, the end-of-life environmental fate of such materials is not adequately understood. Non-isocyanate polyhydroxyurethanes (PHUs) are green engineering materials with huge potential to replace traditional polyurethanes. Despite this immense potential, a number of questions about their environmental fate remain unanswered. The present study investigated the extent and mechanisms underlying soil biodegradation of PHUs and determined whether the deterioration of PHUs within starch bioplastics (ST) can improve the biodegradation of starch (ST)-PHU hybrids. Soil microbiomes managed to effectively and quickly digest not only PHUs but also ST-PHU hybrids. All ST-PHU hybrids were characterized by exceptional biodegradability with mass losses of up to ~88% following a soil burial time of only 120 days. The biodegradation of ST-alone bioplastics was 69% under identical conditions. The presence of cellulose nanocrystals (CNC) reduced the potential for the soil microbial community to degrade nanohybrids (ST-PHU-CNC). Microbially digested bioplastics with PHU presented less stages of thermal degradation, and reduced intensities of FTIR, NMR and XPS signals compared to the original films, indicating improvement of the biodegradation mechanism. These findings suggested the positive environmental implications of PHU in improving the bioplastic's degradation and their potential for future applications.

Programmed Death of Injured Pseudomonas aeruginosa on Mechano-Bactericidal Surfaces

Mechano-bactericidal surfaces deliver lethal effects to contacting bacteria. Until now, cell death has been attributed to the mechanical stress imparted to the bacterial cell envelope by the surface nanostructures; however, the process of bacterial death encountering nanostructured surfaces has not been fully illuminated. Here, we perform an in-depth investigation of the mechano-bactericidal action of black silicon (bSi) surfaces toward Gram-negative bacteria Pseudomonas aeruginosa. We discover that the mechanical injury is not sufficient to kill the bacteria immediately due to the survival of the inner plasma membrane. Instead, such sublethal mechanical injury leads to apoptosis-like death (ALD) in affected bacteria. In addition, when the mechanical stress is removed, the self-accumulated reactive oxygen species (ROS) incur poststress ALD in damaged cells in a nonstressed environment, revealing that the mechano-bactericidal actions have sustained physiological effects on the bacterium. This work creates a new facet and can introduce many new regulation tools to this field.

Silicon-Doped Graphene Oxide Quantum Dots as Efficient Nanoconjugates for Multifunctional Nanocomposites

Graphene oxide quantum dots (GOQDs) hold great promise as a new class of high-performance carbonaceous nanomaterials due to their numerous functional properties, such as tunable photoluminescence (PL), excellent thermal and chemical stability, and superior biocompatibility. In this study, we developed a facile, one-pot, and effective strategy to engineer the interface of GOQDs through covalent doping with silicon. The successful covalent attachment of the silane dopant with pendant vinyl groups to the edges of the GOQDs was confirmed by an in-depth investigation of the structural and morphological characteristics. The Si-GOQD nanoconjugates had an average dimension of ∼8 nm, with a graphite-structured core and amorphous carbon on their shell. We further used the infrared nanoimaging based on scattering-type scanning near-field optical microscopy to unveil the spectral near-field response of GOQD samples and to measure the nanoscale IR response of its network; we then demonstrated their distinct domains with strongly enhanced near fields. The doping of Si atoms into the sp²-hybridized graphitic framework of GOQDs also led to tailored PL emissions. We then sought to explore the potential applications of Si-GOQDs on the surface of plastic films where poly(dimethylsiloxane) (PDMS) served as a bridge to tightly anchor the Si-GOQDs to the surface. The bi-layered coated films which were built with co-assembly of Si-GOQDs and PDMS contributed to suppressing the transmission of water molecules due to the generation of compact and less accessible passing sites, achieving a nearly twofold reduction in water permeability compared to the single-layered coated films. The nanoindentation and PeakForce quantitative nanomechanical mapping showed that Si-GOQD-coated substrates were softer and more deformable than those coated only with PDMS. The co-assembly of PDMS and Si-GOQDs yielded films that were less stiff than those made from PDMS alone. Our findings provided conceptual insights into the importance of nanoscale surface engineering of GOQDs in conferring excellent dispersibility and enhancing the performance of nanocomposite films.

Surface Architecture Influences the Rigidity of Candida albicans Cells

Atomic force microscopy (AFM) was used to investigate the morphology and rigidity of the opportunistic pathogenic yeast, Candida albicans ATCC 10231, during its attachment to surfaces of three levels of nanoscale surface roughness. Non-polished titanium (npTi), polished titanium (pTi), and glass with respective average surface roughness (S_a) values of 389 nm, 14 nm, and 2 nm, kurtosis (S_kur) values of 4, 16, and 4, and skewness (S_skw) values of 1, 4, and 1 were used as representative examples of each type of nanoarchitecture. Thus, npTi and glass surfaces exhibited similar S_skw and S_kur values but highly disparate S_a. C. albicans cells that had attached to the pTi surfaces exhibited a twofold increase in rigidity of 364 kPa compared to those yeast cells attached to the surfaces of npTi (164 kPa) and glass (185 kPa). The increased rigidity of the C. albicans cells on pTi was accompanied by a distinct round morphology, condensed F-actin distribution, lack of cortical actin patches, and the negligible production of cell-associated polymeric substances; however, an elevated production of loose extracellular polymeric substances (EPS) was observed. The differences in the physical response of C. albicans cells attached to the three surfaces suggested that the surface nanoarchitecture (characterized by skewness and kurtosis), rather than average surface roughness, could directly influence the rigidity of the C. albicans cells. This work contributes to the next-generation design of antifungal surfaces by exploiting surface architecture to control the extent of biofilm formation undertaken by yeast pathogens and highlights the importance of performing a detailed surface roughness characterization in order to identify and discriminate between the surface characteristics that may influence the extent of cell attachment and the subsequent behavior of the attached cells.

Advancing of 3D-Printed Titanium Implants with Combined Antibacterial Protection Using Ultrasharp Nanostructured Surface and Gallium-Releasing Agents

This paper presents the development of advanced Ti implants with enhanced antibacterial activity. The implants were engineered using additive manufacturing three-dimensional (3D) printing technology followed by surface modification with electrochemical anodization and hydrothermal etching, to create unique hierarchical micro/nanosurface topographies of microspheres covered with sharp nanopillars that can mechanically kill bacteria in contact with the surface. To achieve enhanced antibacterial performance, fabricated Ti implant models were loaded with gallium nitrate as an antibacterial agent. The antibacterial efficacy of the fabricated substrates with the combined action of sharp nanopillars and locally releasing gallium ions (Ga³⁺) was evaluated toward Staphylococcus aureus and Pseudomonas aeruginosa. Results confirm the significant antibacterial performance of Ga³⁺-loaded substrates with a 100% eradication of bacteria. The nanopillars significantly reduced bacterial attachment and prevented biofilm formation while also killing any bacteria remaining on the surface. Furthermore, 3D-printed surfaces with microspheres of diameter 5-30 μm and interspaces of 12-35 μm favored the attachment of osteoblast-like MG-63 cells, as confirmed via the assessment of their attachment, proliferation, and viability. This study provides important progress toward engineering of next-generation 3D-printed implants, that combine surface chemistry and structure to achieve a highly efficacious antibacterial surface with dual cytocompatibility to overcome the limitations of conventional Ti implants.

Functional nanomaterials, synergisms, and biomimicry for environmentally benign marine antifouling technology

Marine biofouling remains one of the key challenges for maritime industries, both for seafaring and stationary structures. Currently used biocide-based approaches suffer from significant drawbacks, coming at a significant cost to the environment into which the biocides are released, whereas novel environmentally friendly approaches are often difficult to translate from lab bench to commercial scale. In this article, current biocide-based strategies and their adverse environmental effects are briefly outlined, showing significant gaps that could be addressed through advanced materials engineering. Current research towards the use of natural antifouling products and strategies based on physio-chemical properties is then reviewed, focusing on the recent progress and promising novel developments in the field of environmentally benign marine antifouling technologies based on advanced nanocomposites, synergistic effects and biomimetic approaches are discussed and their benefits and potential drawbacks are compared to existing techniques.

Tailoring Additively Manufactured Titanium Implants for Short-Time Pediatric Implantations with Enhanced Bactericidal Activity

Paediatric titanium (Ti) implants are used for the short-term fixation of fractures, after which they are removed. However, bone overgrowth on the implant surface can complicate their removal. The current Ti implants research focuses on improving their osseointegration and antibacterial properties for long-term use while overlooking the requirements of temporary implants. This paper presents the engineering of additively manufactured Ti implants with antibacterial properties and prevention of bone cell overgrowth. 3D-printed implants were fabricated followed by electrochemical anodization to generate vertically aligned titania nanotubes (TNTs) on the surface with specific diameters (∼100 nm) to reduce cell attachment and proliferation. To achieve enhanced antibacterial performance, TNTs were coated with gallium nitrate as antibacterial agent. The physicochemical characteristics of these implants assessed by the attachment, growth and viability of osteoblastic MG-63 cells showed significantly reduced cell attachment and proliferation, confirming the ability of TNTs surface to avoid cell overgrowth. Gallium coated TNTs showed strong antibacterial activity against S. aureus and P. aeruginosa with reduced bacterial attachment and high rates of bacterial death. Thus a new approach for the engineering of temporary Ti implants with enhanced bactericidal properties with reduced bone cell attachment is demonstrated as a new strategy toward a new generation of short-term implants in paediatrics.

Robust and Eco-Friendly Superhydrophobic Starch Nanohybrid Materials with Engineered Lotus Leaf Mimetic Multiscale Hierarchical Structures

The use of superhydrophobic surfaces in a broad range of applications is receiving a great deal of attention due to their numerous functionalities. However, fabricating these surfaces using low-cost raw materials through green and fluorine-free routes has been a bottleneck in their industrial deployment. This work presents a facile and environmentally friendly strategy to prepare mechanically robust superhydrophobic surfaces with engineered lotus leaf mimetic multiscale hierarchical structures via a hybrid route combining soft imprinting and spin-coating. Direct soft-imprinting lithography onto starch/polyhydroxyurethane/cellulose nanocrystal (SPC) films formed micro-scaled features resembling the pillar architecture of lotus leaf. Spin-coating was then used to assemble a thin layer of low-surface-energy poly(dimethylsiloxane) (PDMS) over these microstructures. Silica nanoparticles (SNPs) were grafted with vinyltriethoxysilane (VTES) to form functional silica nanoparticles (V-SNPs) and subsequently used for the fabrication of superhydrophobic coatings. A further modification of PDMS@SPC film with V-SNPs enabled the interlocking of V-SNPs microparticles within the cross-linked PDMS network. The simultaneous introduction of hierarchical microscale surface topography, the low surface tension of the PDMS layer, and the nanoscale roughness induced by V-SNPs contributed to the fabrication of a superhydrophobic interface with a water contact angle (WCA) of ∼150° and a sliding angle (SA) of <10°. The PDMS/V-SNP@SPC films showed an ∼52% reduction in water vapor transmission rate compared to that of uncoated films. These results indicated that the coating served as an excellent moisture barrier and imparted good hydrophobicity to the film substrate. The coated film surfaces were able to withstand extensive knife scratches, finger-rubbing, jet-water impact, a sandpaper-abrasion test for 20 cycles, and a tape-peeling test for ∼10 repetitions without losing superhydrophobicity, suggesting superior mechanical durability. Self-cleaning behavior was also demonstrated when the surfaces were cleared of artificial dust and various food liquids. The green and innovative approach presented in the current study can potentially serve as an attractive new tool for the development of robust superhydrophobic surfaces without adverse environmental consequences.

Plasma and Polymers: Recent Progress and Trends

Plasma-enhanced synthesis and modification of polymers is a field that continues to expand and become increasingly more sophisticated. The highly reactive processing environments afforded by the inherently dynamic nature of plasma media are often superior to ambient or thermal environments, offering substantial advantages over other processing methods. The fluxes of energy and matter toward the surface enable rapid and efficient processing, whereas the charged nature of plasma-generated particles provides a means for their control. The range of materials that can be treated by plasmas is incredibly broad, spanning pure polymers, polymer-metal, polymer-wood, polymer-nanocarbon composites, and others. In this review, we briefly outline some of the recent examples of the state-of-the-art in the plasma-based polymer treatment and functionalization techniques.

Towards antiviral polymer composites to combat COVID-19 transmission

Polymer matrix composite materials have the capacity to aid the indirect transmission of viral diseases. Published research shows that respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2 or COVID‐19), can attach to polymer substrata as a result of being contacted by airborne droplets resulting from infected people sneezing or coughing in close proximity. Polymer matrix composites are used to produce a wide range of products that are “high‐touch” surfaces, such as sporting goods, laptop computers and household fittings, and these surfaces can be readily contaminated by pathogens. This article reviews published research on the retention of SARS‐CoV‐2 and other virus types on plastics. The factors controlling the viral retention time on plastic surfaces are examined and the implications for viral retention on polymer composite materials are discussed. Potential strategies that can be used to impart antiviral properties to polymer composite surfaces are evaluated. These strategies include modification of the surface composition with biocidal agents (e.g., antiviral polymers and nanoparticles) and surface nanotexturing. The potential application of these surface modification strategies in the creation of antiviral polymer composite surfaces is discussed, which opens up an exciting new field of research for composite materials.

Translocation of silica nanospheres through giant unilamellar vesicles (GUVs) induced by a high frequency electromagnetic field

Membrane model systems capable of mimicking live cell membranes were used for the first time in studying the effects arising from electromagnetic fields (EMFs) of 18 GHz where membrane permeability was observed following exposure.

Nanoscale Surface Roughness Influences Candida albicans Biofilm Formation

The microbial contamination of surfaces presents a significant challenge due to the adverse effects associated with biofilm formation, particularly on implantable devices. Here, the attachment and biofilm formation of the opportunistic human pathogen, Candida albicans ATCC 10231, were studied on surfaces with decreasing magnitudes of nanoscale roughness. The nanoscale surface roughness of nonpolished titanium, polished titanium, and glass was characterized according to average surface roughness, skewness, and kurtosis. Nonpolished titanium, polished titanium, and glass possessed average surface roughness (S_a) values of 350, 20, and 2.5 nm; skewness (S_skw) values of 1.0, 4.0, and 1.0; and (S_kur) values of 3.5, 16, and 4, respectively. These unique characteristics of the surface nanoarchitecture were found to play a key role in limiting C. albicans attachment and modulating the functional phenotypic changes associated with biofilm formation. Our results suggest that surfaces with a specific combination of surface topographical parameters could prevent the attachment and biofilm formation of C. albicans. After 7 days, the density of attached C. albicans cells was recorded to be 230, 70, and 220 cells mm^-2 on nonpolished titanium, polished titanium, and glass surfaces, respectively. Despite achieving a very low attachment density, C. albicanscells were only observed to produce hyphae associated with biofilm formation on nonpolished titanium surfaces, possessing the highest degree of surface roughness (S_a = 350 nm). This study provides a more comprehensive picture of the impact of surface architectures on C. albicans attachment, which is beneficial for the design of antifungal surfaces.

Antibacterial Action of Nanoparticles by Lethal Stretching of Bacterial Cell Membranes

It is commonly accepted that nanoparticles (NPs) can kill bacteria; however, the mechanism of antimicrobial action remains obscure for large NPs that cannot translocate the bacterial cell wall. It is demonstrated that the increase in membrane tension caused by the adsorption of NPs is responsible for mechanical deformation, leading to cell rupture and death. A biophysical model of the NP-membrane interactions is presented which suggests that adsorbed NPs cause membrane stretching and squeezing. This general phenomenon is demonstrated experimentally using both model membranes and Pseudomonas aeruginosa and Staphylococcus aureus, representing Gram-positive and Gram-negative bacteria. Hydrophilic and hydrophobic quasi-spherical and star-shaped gold (Au)NPs are synthesized to explore the antibacterial mechanism of non-translocating AuNPs. Direct observation of nanoparticle-induced membrane tension and squeezing is demonstrated using a custom-designed microfluidic device, which relieves contraction of the model membrane surface area and eventual lipid bilayer collapse. Quasi-spherical nanoparticles exhibit a greater bactericidal action due to a higher interactive affinity, resulting in greater membrane stretching and rupturing, corroborating the theoretical model. Electron microscopy techniques are used to characterize the NP-bacterial-membrane interactions. This combination of experimental and theoretical results confirm the proposed mechanism of membrane-tension-induced (mechanical) killing of bacterial cells by non-translocating NPs.

Author Correction: Roadmap for naming uncultivated Archaea and Bacteria

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Mechano-Bactericidal Titanium Surfaces for Bone Tissue Engineering

Despite advances in the development of bone substitutes and strict aseptic procedures, the majority of failures in bone grafting surgery are related to nosocomial infections. Development of biomaterials combining both osteogenic and antibiotic activity is, therefore, a crucial public health issue. Herein, two types of intrinsically bactericidal titanium supports were fabricated by using commercially scalable techniques: plasma etching or hydrothermal treatment, which display two separate mechanisms of mechano-bactericidal action. Hydrothermal etching produces a randomly nanostructured surface with sharp nanosheet protrusions killing bacteria via cutting of the cell membrane, whereas plasma etching of titanium produces a microscale two-tier hierarchical topography that both reduce bacterial attachment and rupture those bacteria that encounter the surface. The adhesion, growth, and proliferation of human adipose-derived stem cells (hASCs) on the two mechano-bactericidal topographies were assessed. Both types of supports allowed the growth and proliferation of the hASCs in the same manner and cells retained their stemness and osteogenic potential. Furthermore, these supports induced osteogenic differentiation of hASCs without the need of differentiation factors, demonstrating their osteoinductive properties. This study proves that these innovative mechano-bactericidal titanium surfaces with both regenerative and bactericidal properties are a promising solution to improve the success rate of reconstructive surgery.

Electrospun Nanodiamond-Silk Fibroin Membranes: A Multifunctional Platform for Biosensing and Wound-Healing Applications

Next generation wound care technology capable of diagnosing wound parameters, promoting healthy cell growth, and reducing pathogenic infections noninvasively would provide patients with an improved standard of care and accelerated wound repair. Temperature is one of the indicating biomarkers specific to chronic wounds. This work reports a hybrid, multifunctional optical material platform-nanodiamond (ND)-silk membranes as biopolymer dressings capable of temperature sensing and promoting wound healing. The hybrid structure was fabricated through electrospinning, and 3D submicron fibrous membranes with high porosity were formed. Silk fibers are capable of compensating for the lack of an extracellular matrix at the wound site, supporting the wound-healing process. Negatively charged nitrogen vacancy (NV^-) color centers in NDs exhibit optically detected magnetic resonance (ODMR) and act as nanoscale thermometers. This can be exploited to sense temperature variations associated with the presence of infection or inflammation in a wound, without physically removing the dressing. Our results show that the presence of NDs in the hybrid ND-silk membranes improves the thermal stability of silk fibers. NV^- color centers in NDs embedded in silk fibers exhibit well-retained fluorescence and ODMR. Using the NV^- centers as fluorescent nanoscale thermometers, we achieved temperature sensing in 25-50 °C, including the biologically relevant temperature window, for cell-grown ND-silk membranes. An enhancement (∼1.5× on average) in the temperature sensitivity of the NV^- centers was observed for the hybrid materials. The hybrid membranes were further tested in vivo in a murine wound-healing model and demonstrated biocompatibility and equivalent wound closure rates as the control wounds. Additionally, the hybrid ND-silk membranes exhibited selective antifouling and biocidal propensity toward Gram-negative Pseudomonas aeruginosa and Escherichia coli, while no effect was observed on Gram-positive Staphylococcus aureus.

Use of Synergistic Interactions to Fabricate Transparent and Mechanically Robust Nanohybrids Based on Starch, Non-Isocyanate Polyurethanes, and Cellulose Nanocrystals

Materials based on petroleum-based resources have aroused widespread concern because of their environmental and healthcare footprints. Cellulose nanocrystals (CNCs) are at the cutting edge of current research because of their great promise in developing sustainable and high-performance materials. To establish a comprehensive understanding of the synergistic reinforcement effect of CNCs, we introduced a new method to fabricate all-green, transparent, and mechanically robust nanohybrid materials using CNCs in conjunction with gelatinized starch (GS) and polyhydroxyurethanes (PHUs). The synergistic interaction between the CNC skeleton and the GS/PHU network enabled us to span exceptionally stiff nanohybrids that could withstand up to 8.5 MPa tensile strength. The tunable mechanical properties and enhanced thermal stability in these nanohybrids primarily arise from the presence of dense hydroxyl groups on the CNCs' surface, which offer a robust scaffold for fortified hydrogen bonds to form with GS/PHU domains. The multiple intramolecular hydrogen bonds synergistically served as highly stable associations and concurrently facilitated energy dissipation and transferred the stress across the interfacial region. The rational design of the molecular interactions presented in this work provided increased opportunities to build nanohybrids with outstanding mechanical performance. More broadly, the insights afforded by this study not only delivered a better understanding on the molecular-level interactions in the CNC/GS/PHU system but also enriched the potential for the commercial exploration of tunable cellulosic nanohybrid materials.

Assessment of interfacial interactions between starch and non-isocyanate polyurethanes in their hybrids

Manufacturing of multifunctional materials through blending is a promising route for improving performance of biopolymers including starch. Non-isocyanate polyurethanes (NIPUs) are an emerging group of green materials. Understanding the mechanism of interaction between starch and NIPU not only highlights underlying chemistry but also offers an opportunity to tailor the properties and functions of starch-NIPU hybrids. We investigated the interfacial interactions between starch and NIPU to pave the way towards development of high-performance green materials. Multiple analyses revealed that NIPU interacted effectively with starch chains via intermolecular hydrogen bonds. We showed that NIPU domains can efficiently interact with the small portion of starch skeleton at interfacial region and they are only moderately miscible. Incorporation of either component above certain ratio resulted in a phase separation. This work contributes towards understanding of interfacial chemistry between starch and NIPUs and enables tailoring the interface for facile engineering of starch-NIPU hybrids.

Single shot multispectral multidimensional imaging using chaotic waves

Multispectral imaging technology is a valuable scientific tool for various applications in astronomy, remote sensing, molecular fingerprinting, and fluorescence imaging. In this study, we demonstrate a single camera shot, lensless, interferenceless, motionless, non-scanning, space, spectrum, and time resolved five-dimensional incoherent imaging technique using tailored chaotic waves with quasi-random intensity and phase distributions. Chaotic waves can distinctly encode spatial and spectral information of an object in single self-interference intensity distribution. In this study, a tailored chaotic wave with a nearly pure phase function and lowest correlation noise is generated using a quasi-random array of pinholes. A unique sequence of signal processing techniques is applied to extract all possible spatial and spectral channels with the least entropy. The depth-wavelength reciprocity is exploited to see colour from depth and depth from colour and the physics of beam propagation is exploited to see at one depth by calibrating at another.

Direct Measurement of Temperature Diffusivity of Nanocellulose-Doped Biodegradable Composite Films

The thermal properties of novel nanomaterials play a significant role in determining the performance of the material in technological applications. Herein, direct measurement of the temperature diffusivity of nanocellulose-doped starch-polyurethane nanocomposite films was carried out by the micro-contact method. Polymer films containing up to 2 wt%. of nanocellulose were synthesised by a simple chemical process and are biodegradable. Films of a high optical transmittance T≈80% (for a 200 μm thick film), which were up to 44% crystalline, were characterised. Two different modalities of temperature diffusivity based on (1) a resistance change and (2) micro-thermocouple detected voltage modulation caused by the heat wave, were used for the polymer films with cross sections of ∼100 μm thickness. Twice different in-plane α‖ and out-of-plane α⟂ temperature diffusivities were directly determined with high fidelity: α‖=2.12×10-7 m2/s and α⟂=1.13×10-7 m2/s. This work provides an example of a direct contact measurement of thermal properties of nanocellulose composite biodegradable polymer films. The thermal diffusivity, which is usually high in strongly interconnected networks and crystals, was investigated for the first time in this polymer nanocomposite.

Roadmap for naming uncultivated Archaea and Bacteria

The assembly of single-amplified genomes (SAGs) and metagenome-assembled genomes (MAGs) has led to a surge in genome-based discoveries of members affiliated with Archaea and Bacteria, bringing with it a need to develop guidelines for nomenclature of uncultivated microorganisms. The International Code of Nomenclature of Prokaryotes (ICNP) only recognizes cultures as 'type material', thereby preventing the naming of uncultivated organisms. In this Consensus Statement, we propose two potential paths to solve this nomenclatural conundrum. One option is the adoption of previously proposed modifications to the ICNP to recognize DNA sequences as acceptable type material; the other option creates a nomenclatural code for uncultivated Archaea and Bacteria that could eventually be merged with the ICNP in the future. Regardless of the path taken, we believe that action is needed now within the scientific community to develop consistent rules for nomenclature of uncultivated taxa in order to provide clarity and stability, and to effectively communicate microbial diversity.

Tilted black-Si: ∼0.45 form-birefringence from sub-wavelength needles

The self-organised conical needles produced by plasma etching of silicon (Si), known as black silicon (b-Si), create a form-birefringent surface texture when etching of Si orientated at angles of θ_i < 50 - 70^° (angle between the Si surface and vertical plasma E-field). The height of the needles in the form-birefringent region following 15 min etching was d ∼ 200 nm and had a 100 μm width of the optical retardance/birefringence, characterised using polariscopy. The height of the b-Si needles corresponds closely to the skin-depth of Si ∼λ/4 for the visible spectral range. Reflection-type polariscope with a voltage-controlled liquid-crystal retarder is proposed to directly measure the retardance Δn × d/λ ≈ 0.15 of the region with tilted b-Si needles. The quantified form birefringence of Δn = -0.45 over λ = 400 - 700 nm spectral window was obtained. Such high values of Δn at visible wavelengths can only be observed in the most birefringence calcite or barium borate as well as in liquid crystals. The replication of b-Si into Ni-shim with high fidelity was also demonstrated and can be used for imprinting of the b-Si nanopattern into other materials.

Three-Dimensional Hierarchical Wrinkles on Polymer Films: From Chaotic to Ordered Antimicrobial Topographies

Microbial contamination of polymer surfaces has become a significant challenge in domestic, industrial, and biomedical applications. Recent progress in our understanding of how topographical features of different length scales can be used to effectively and selectively control the attachment and proliferation of different cell types has provided an alternative strategy for imparting antibacterial activity to these surfaces. Among the well-recognized engineered models of antibacterial surface topographies, self-organized wrinkles have shown particular promise with respect to their antimicrobial characteristics. Here, we critically review the mechanisms by which wrinkles form on the surface of different types of polymer material and how they interact with various biomolecules and cell types. We also discuss the feasibility of using this antimicrobial strategy in real-life biomedical applications.

Polymerization-Induced Phase Segregation and Self-Assembly of Siloxane Additives to Provide Thermoset Coatings with a Defined Surface Topology and Biocidal and Self-Cleaning Properties

In this work, we report on the incorporation of a siloxane copolymer additive, poly((2-phenylethyl) methylsiloxane)-co(1-phenylethyl) methylsiloxane)-co-dimethylsiloxane), which is fully soluble at room temperature, in a rapid-cure thermoset polyester coating formulation. The additive undergoes polymerization-induced phase segregation (PIPS) to self-assemble on the coating surface as discrete discoid nanofeatures during the resin cure process. Moreover, the copolymer facilitates surface co-segregation of titanium dioxide pigment microparticulate present in the coating. Depending on the composition, the coatings can display persistent superhydrophobicity and self-cleaning properties and, surprisingly, the titanium dioxide pigmented coatings that include the siloxane copolymer additive display high levels of antibacterial performance against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria. This antibacterial performance is believed to be associated with the unique surface topology of these coatings, which comprise stimuli-responsive discoid nanofeatures. This paper provides details of the surface morphology of the coatings and how these relates to the antimicrobial properties of the coating.

Tunable morphological changes of asymmetric titanium nanosheets with bactericidal properties

HYPOTHESIS

Titanium and titanium alloys are often the most popular choice of material for the manufacture of medical implants; however, they remain susceptible to the risk of device-related infection caused by the presence of pathogenic bacteria. Hydrothermal etching of titanium surfaces, to produce random nanosheet topologies, has shown remarkable ability to inactivate pathogenic bacteria via a physical mechanism. We expect that systematic tuning of the nanosheet morphology by controlling fabrication parameters, such as etching time, will allow for optimisation of the surface pattern for superior antibacterial efficacy.

EXPERIMENTS

Using time-dependent hydrothermal processing of bulk titanium, we fabricated bactericidal nanosheets with variable nanoedge morphologies according to a function of etching time. A systematic study was performed to compare the bactericidal efficiency of nanostructured titanium surfaces produced at 0.5, 1, 2, 3, 4, 5, 6, 24 and 60 h of hydrothermal etching.

FINDINGS

Titanium surfaces hydrothermally treated for a period of 6 h were found to achieve maximal antibacterial efficiency of 99 ± 3% against Gram-negative Pseudomonas aeruginosa and 90 ± 9% against Gram-positive Staphylococcus aureus bacteria, two common human pathogens. These surfaces exhibited nanosheets with sharp edges of approximately 10 nm. The nanotopographies presented in this work exhibit the most efficient mechano-bactericidal activity against both Gram-negative and Gram-positive bacteria of any nanostructured titanium topography reported thus far.

The idiosyncratic self-cleaning cycle of bacteria on regularly arrayed mechano-bactericidal nanostructures

Nanostructured mechano-bactericidal surfaces represent a promising technology to prevent the incidence of microbial contamination on a variety of surfaces and to avoid bacterial infection, particularly with antibiotic resistant strains. In this work, a regular array of silicon nanopillars of 380 nm height and 35 nm diameter was used to study the release of bacterial cell debris off the surface, following inactivation of the cell due to nanostructure-induced rupture. It was confirmed that substantial bactericidal activity was achieved against Gram-negative Pseudomonas aeruginosa (85% non-viable cells) and only modest antibacterial activity towards Staphylococcus aureus (8% non-viable cells), as estimated by measuring the proportions of viable and non-viable cells via fluorescence imaging. In situ time-lapse AFM scans of the bacteria-nanopillar interface confirmed the removal rate of the dead P. aeruginosa cells from the surface to be approximately 19 minutes per cell, and approximately 11 minutes per cell for dead S. aureus cells. These results highlight that the killing and dead cell detachment cycle for bacteria on these substrata are dependant on the bacterial species and the surface architecture studied and will vary when these two parameters are altered. The outcomes of this work will enhance the current understanding of antibacterial nanostructures, and impact upon the development and implementation of next-generation implants and medical devices.

Engineering the Interface: Nanodiamond Coating on 3D-Printed Titanium Promotes Mammalian Cell Growth and Inhibits Staphylococcus aureus Colonization

Additively manufactured selective laser melted titanium (SLM-Ti) opens the possibility of tailored medical implants for patients. Despite orthopedic implant advancements, significant problems remain with regard to suboptimal osseointegration at the interface between the implant and the surrounding tissue. Here, we show that applying a nanodiamond (ND) coating onto SLM-Ti scaffolds provides an improved surface for mammalian cell growth while inhibiting colonization of Staphylococcus aureus bacteria. Owing to the simplicity of our methodology, the approach is suitable for coating SLM-Ti geometries. The ND coating achieved 32 and 29% increases in cell density of human dermal fibroblasts and osteoblasts, respectively, after 3 days of incubation compared with the uncoated SLM-Ti substratum. This increase in cell density complements an 88% reduction in S. aureus detected on the ND-coated SLM-Ti substrata. This study paves a way to create facile antifouling SLM-Ti structures for biomedical implants.

Switchable Dual-Function and Bioresponsive Materials to Control Bacterial Infections

The colonization of undesired bacteria on the surface of devices used in biomedical and clinical applications has become a persistent problem. Different types of single-function (cell resistance or bactericidal) bioresponsive materials have been developed to cope with this problem. Even though these materials meet the basic requirements of many biomedical and clinical applications, dual-function (cell resistance and biocidal) bioresponsive materials with superior design and function could be better suited for these applications. The past few years have witnessed the emergence of a new class of dual-function materials that can reversibly switch between cell-resistance and biocidal functions in response to external stimuli. These materials are finding increased applications in biomedical devices, tissue engineering, and drug-delivery systems. This review highlights the recent advances in design, structure, and fabrication of dual-function bioresponsive materials and discusses translational challenges and future prospects for research involving these materials.

The Fate of Osteoblast-Like MG-63 Cells on Pre-Infected Bactericidal Nanostructured Titanium Surfaces

Biomaterials that have been newly implanted inside the body are the substratum targets for a "race for the surface", in which bacterial cells compete against eukaryotic cells for the opportunity to colonize the surface. A victory by the former often results in biomaterial-associated infections, which can be a serious threat to patient health and can undermine the function and performance of the implant. Moreover, bacteria can often have a 'head start' if implant contamination has taken place either prior to or during the surgery. Current prevention and treatment strategies often rely on systemic antibiotic therapies, which are becoming increasingly ineffective due to a growing prevalence of antibiotic-resistant bacteria. Nanostructured surfaces that kill bacteria by physically rupturing bacterial cells upon contact have recently emerged as a promising solution for the mitigation of bacterial colonization of implants. Furthermore, these nanoscale features have been shown to enhance the adhesion and proliferation of eukaryotic cells, which is a key to, for example, the successful osseointegration of load-bearing titanium implants. The bactericidal activity and biocompatibility of such nanostructured surfaces are often, however, examined separately, and it is not clear to what extent bacterial cell-surface interactions would affect the subsequent outcomes of host-cell attachment and osseointegration processes. In this study, we investigated the ability of bactericidal nanostructured titanium surfaces to support the attachment and growth of osteoblast-like MG-63 human osteosarcoma cells, despite them having been pre-infected with pathogenic bacteria. MG-63 is a commonly used osteoblastic model to study bone cell viability, adhesion, and proliferation on the surfaces of load-bearing biomaterials, such as titanium. The nanostructured titanium surfaces used here were observed to kill the pathogenic bacteria, whilst simultaneously enhancing the growth of MG-63 cells in vitro when compared to that occurring on sterile, flat titanium surfaces. These results provide further evidence in support of nanostructured bactericidal surfaces being used as a strategy to help eukaryotic cells win the "race for the surface" against bacterial cells on implant materials.

Nanoscale optical and structural characterisation of silk

The nanoscale composition of silk defining its unique properties via a hierarchial structural anisotropy needs to be analysed at the highest spatial resolution of tens of nanometers corresponding to the size of fibrils made of β-sheets, which are the crystalline building blocks of silk. Nanoscale optical and structural properties of silk have been measured from 100 nm thick longitudinal slices of silk fibers with ca. 10 nm resolution, the highest so far. Optical sub-wavelength resolution in hyperspectral mapping of absorbance and molecular orientation were carried out for comparison at IR wavelengths of 2-10 μm using synchrotron radiation. A reliable distinction of transmission changes by only 1-2% as the anisotropy of amide bands was obtained from nanometer-thin slices of silk.

Interaction of Giant Unilamellar Vesicles with the Surface Nanostructures on Dragonfly Wings

The waxy epicuticle of dragonfly wings contains a unique nanostructured pattern that exhibits bactericidal properties. In light of emerging concerns of antibiotic resistance, these mechano-bactericidal surfaces represent a particularly novel solution by which bacterial colonization and the formation of biofilms on biomedical devices can be prevented. Pathogenic bacterial biofilms on medical implant surfaces cause a significant number of human deaths every year. The proposed mechanism of bactericidal activity is through mechanical cell rupture; however, this is not yet well understood and has not been well characterized. In this study, we used giant unilamellar vesicles (GUVs) as a simplified cell membrane model to investigate the nature of their interaction with the surface of the wings of two dragonfly species, Austrothemis nigrescens and Trithemis annulata, sourced from Victoria, Australia, and the Baix Ebre and Terra Alta regions of Catalonia, Spain. Confocal laser scanning microscopy and cryo-scanning electron microscopy techniques were used to visualize the interactions between the GUVs and the wing surfaces. When exposed to both natural and gold-coated wing surfaces, the GUVs were adsorbed on the surface, exhibiting significant deformation, in the process of membrane rupture. Differences between the tensile rupture limit of GUVs composed of 1,2-dioleoyl- sn-glycero-3-phosphocholine and the isotropic tension generated from the internal osmotic pressure were used to indirectly determine the membrane tensions, generated by the nanostructures present on the wing surfaces. These were estimated as being in excess of 6.8 mN m^-1, the first experimental estimate of such mechano-bactericidal surfaces. This simple model provides a convenient bottom-up approach toward understanding and characterizing the bactericidal properties of nanostructured surfaces.