Advances in uremic toxin detection and monitoring in the management of chronic kidney disease progression to end-stage renal disease

Patients with end-stage kidney disease (ESKD) rely on dialysis to remove toxins and stay alive. However, hemodialysis alone is insufficient to completely remove all/major uremic toxins, resulting in the accumulation of specific toxins over time. The complexity of uremic toxins and their varying clearance rates across different dialysis modalities poses significant challenges, and innovative approaches such as microfluidics, biomarker discovery, and point-of-care testing are being investigated. This review explores recent advances in the qualitative and quantitative analysis of uremic toxins and highlights the use of innovative methods, particularly label-mediated and label-free surface-enhanced Raman spectroscopy, primarily for qualitative detection. The ability to analyze uremic toxins can optimize hemodialysis settings for more efficient toxin removal. Integration of multiple omics disciplines will also help identify biomarkers and understand the pathogenesis of ESKD, provide deeper understanding of uremic toxin profiling, and offer insights for improving hemodialysis programs. This review also highlights the importance of early detection and improved understanding of chronic kidney disease to improve patient outcomes.

Detection of micro-plasma-induced exosomes secretion in a fibroblast-melanoma co-culture model

BACKGROUND

Melanoma is a highly aggressive tumor and a significant cause of skin cancer-related death. Timely diagnosis and treatment require identification of specific biomarkers in exosomes secreted by melanoma cells. In this study, label-free surface-enhanced Raman spectroscopy (SERS) method with size-matched selectivity was used to detect membrane proteins in exosomes released from a stimulated environment of fibroblasts (L929) co-cultured with melanoma cells (B16-F10). To promote normal secretion of exosomes, micro-plasma treatment was used to gently induce the co-cultured cells and slightly increase the stress level around the cells for subsequent detection using the SERS method.

RESULTS AND DISCUSSION

Firstly, changes in reactive oxygen species/reactive nitrogen species (ROS/RNS) concentrations in the cellular microenvironment and the viability and proliferation of healthy cells are assessed. Results showed that micro-plasma treatment increased extracellular ROS/RNS levels while modestly reducing cell proliferation without significantly affecting cell survival. Secondly, the particle size of secreted exosomes isolated from the culture medium of L929, B16-F10, and co-cultured cells with different micro-plasma treatment time did not increase significantly under single-cell conditions at short treatment time but might be changed under co-culture condition or longer treatment time. Third, for SERS signals related to membrane protein biomarkers, exosome markers CD9, CD63, and CD81 can be assigned to significant Raman shifts in the range of 943-1030 and 1304-1561 cm-1, while the characteristics SERS peaks of L929 and B16-F10 cells are most likely located at 1394/1404, 1271 and 1592 cm-1 respectively.

SIGNIFICANCE AND NOVELTY

Therefore, this micro-plasma-induced co-culture model provides a promising preclinical approach to understand the diagnostic potential of exosomes secreted by cutaneous melanoma/fibroblasts. Furthermore, the label-free SERS method with size-matched selectivity provides a novel approach to screen biomarkers in exosomes secreted by melanoma cells, aiming to reduce the use of labeling reagents and the processing time traditionally required.

Synergistic surface-enhanced Raman scattering effect to distinguish live SARS-CoV-2 S pseudovirus

The COVID-19 pandemic negatively affected the economy and health security on a global scale, causing a drastic change on lifestyle, calling a need to mitigate further transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. Surface-enhanced Raman spectroscopy (SERS) has shown great potential in the sensitive and rapid detection of various molecules including viruses, through the identification of characteristic peaks of their outer membrane proteins. Accurate detection can be developed through the synergistic integration effect among SERS-active substrate, the appropriate laser wavelength, and the target analyte. In this study, gold nanocavities (Au NC) and Au nanoparticles upon ZrO₂ nano-bowls (Au NPs/pZrO₂) were tested and used as SERS-active substrates in detecting SARS-CoV-2 pseudovirus containing S protein as a surface capsid glycoprotein (SARS-CoV-2 S pseudovirus) and vesicular stomatitis virus G (VSV-G) pseudo-type lentivirus (VSV-G pseudovirus) to demonstrate their virus detection capability. The optimized Au NCs and Au NPs/pZrO₂ substrates were then verified by examining the repetition of measurement, reproducibility, and detection limit. Due to the difference in geometry and composition of the substrates, the characteristic peak-positions of live SARS-CoV-2 S and VSV-G pseudoviruses in the obtained Raman spectra vary, which were also compared with those of inactivated ones. Based on the experimental results, SERS mechanism of each substrate to detect virus is proposed. The formation of hot spots brought by the synergistic integration effect among substrate, analyte, and laser induction may result differences in the obtained SERS spectra.

Retraction: Self-assembled chalcopyrite ternary semiconductor CuBSe2 nanocrystals: solvothermal synthesis and characterisation

Retraction of ‘Self-assembled chalcopyrite ternary semiconductor CuBSe2 nanocrystals: solvothermal synthesis and characterisation’ by Lin-Jer Chen et al., CrystEngComm, 2011, 13, 2909–2914; DOI: 10.1039/C0CE00818D.

Non-Thermal Reactive N2/He Plasma Exposure to Inhibit Epithelial Head and Neck Tumor Cells

The traditional therapy for head and neck cancer patients has several side effects. Hence, regular follow-up care is usually required. Recently, non-thermal micro-plasma was applied to inactivate cancer cells. Such a physical method provides localized energy and reactive oxygen/nitrogen species (ROS/RNS). In this study, the ability of non-oxygen N2/He micro-plasma to inactivate four pharynx squamous carcinomatous cells, namely SAS, CAL 27, FaDu, and Detroit 562, under different exposure durations is evaluated. The four cell lines were affected with regard to proliferation, reduction, and apoptosis-related DNA damage, implying that the cell medium is critical in plasma–cell interaction. This is expected to be a promising method for head and neck cancer cell suppression through plasma-initiated ROS/RNS species under a suitable exposure time.

Recycled Steel Slag as a Porous Adsorbent to Filter Phosphorus-Rich Water with 8 Filtration Circles

Steel slag is a secondary product from steelmaking process through alkaline oxygen furnace or electric arc furnace (EAF). The disposal of steel slag has become a thorny environmental protection issue, and it is mainly used as unbound aggregates, e.g., as a secondary component of asphalt concrete used for road paving. In this study, the characteristics of compacted porous steel slag disc (SSD) and its application in phosphorous (P)-rich water filtration are discussed. The SSD with an optimal porosity of 10 wt% and annealing temperature of 900 °C, denoted as SSD-P (10, 900) meets a compressive strength required by ASTM C159-06, which has the capability of much higher than 90% P removal (with the effluent standard < 4 mg P/L) within 3 h, even after eight filtration times. No harmful substances from SSD have been detected in the filtered water, which complies with the effluent standard ISO 14001. The reaction mechanism for P-rich water filtration is mediated by water, followed by two reaction steps-CaO in SSD hydrolyzed from the matrix of SSD to Ca2+ and reacting with PO43-. However, the microenvironment of water is influenced by the pH value of the P-rich water at different filtration times and the kind of P-rich water with different free positive ion that interferes the reactions of the release of Ca2+. This study demonstrates the application of circular economy in reducing steel slag deposits, filtering P-rich water, and collecting Ca3(PO4)2 precipitate into fertilizers.

Challenges of SERS technology as a non-nucleic acid or -antigen detection method for SARS-CoV-2 virus and its variants

The COVID-19 pandemic has caused a significant burden since December 2019 that has negatively impacted the global economy owing to the fact that the SARS-CoV-2 virus is fast-transmitting and highly contagious. Efforts have been taken to minimize the impact through strict screening measures in country borders in order to isolate potential virus carriers. Effective fast-screening methods are thus needed to identify infected individuals. The standard diagnostic methods for screening SARS-CoV-2 virus have always been to perform nucleic acid-based and serological tests. However, with each having drawbacks on producing false results at very early or later stage after symptoms onset, supplementary techniques are needed to back up these tests. Surface-enhanced Raman spectroscopy (SERS) as a detection technique has continuously advanced throughout the years in terms of sensitivity and capability to detect ultralow concentration of analytes ranging from single molecule to pathogens, to present as a highly potential alternative to known sensing methods. SERS technology as a candidate for an alternative and supplementary diagnostic method for the viral envelope of SARS-CoV-2 virus is presented, comparing its pros and cons to the standard methods and what other aspects it could offer that the other methods are not capable of. Factors that contribute to the detection effectivity of SERS is also discussed to show the advantages and limitations of this technique. Despite its promising capabilities, challenges like sources of SARS-CoV-2 virus and its variations, reliable SERS spectra, mass production of SERS-active substrates, and compliance to regulations for wide-scale testing scenario are highlighted.

Challenges of SERS technology as a non-nucleic acid or -antigen detection method for SARS-CoV-2 virus and its variants

The COVID-19 pandemic has caused a significant burden since December 2019 that has negatively impacted the global economy owing to the fact that the SARS-CoV-2 virus is fast-transmitting and highly contagious. Efforts have been taken to minimize the impact through strict screening measures in country borders in order to isolate potential virus carriers. Effective fast-screening methods are thus needed to identify infected individuals. The standard diagnostic methods for screening SARS-CoV-2 virus have always been to perform nucleic acid-based and serological tests. However, with each having drawbacks on producing false results at very early or later stage after symptoms onset, supplementary techniques are needed to back up these tests. Surface-enhanced Raman spectroscopy (SERS) as a detection technique has continuously advanced throughout the years in terms of sensitivity and capability to detect ultralow concentration of analytes ranging from single molecule to pathogens, to present as a highly potential alternative to known sensing methods. SERS technology as a candidate for an alternative and supplementary diagnostic method for the viral envelope of SARS-CoV-2 virus is presented, comparing its pros and cons to the standard methods and what other aspects it could offer that the other methods are not capable of. Factors that contribute to the detection effectivity of SERS is also discussed to show the advantages and limitations of this technique. Despite its promising capabilities, challenges like sources of SARS-CoV-2 virus and its variations, reliable SERS spectra, mass production of SERS-active substrates, and compliance to regulations for wide-scale testing scenario are highlighted.

Biomimetic Design for a Dual Concentric Porous Titanium Scaffold with Appropriate Compressive Strength and Cells Affinity

In repairing or replacing damaged bones, a dual concentric porous titanium scaffold (P-Tix-y) has emerged as a promising bio-mimic design. Herein, various P-Tix-y were made and sintered with relatively dense (x = 10, 20, or 30% porosity) and loose (y = 45, 55, or 65 porosity) structures. Firstly, NaCl was used as the pore-forming additive and followed by a hydrothermal removal method. The compressive strength of the as-formed P-Tix_y and surface morphology, nanomechanical property, and cells' affinity on the cross-sectioned surface of P-Tix_y (CP-Tix_y) were then characterized. The results demonstrate that the compressive strength of P-Ti10_45, P-Ti20_45, or P-Ti20_55 exhibits a relatively mild decline (e.g., in the range of 181 and 97 MPa, higher than the required value of 70 MPa) and suitable porosities for the intended structure. Nano-hardness on the solid surface of CP-Tix_y shows roughly consistent with that of CP-Ti (i.e., ~8.78 GPa), thus, the porous structure of CP-Tix_y remains mostly unaffected by the addition of NaCl and subsequent sintering process. Most of the surfaces of CP-Tix_y exhibit high fibroblast (L929) cell affinity with low cell mortality. Notably, in the hFOB 1.19 cell adhesion and proliferation test, CP-Ti20_55 and CP-Ti20_65 reveal high cell viability, most probably relating with the assembly of dual porosities with interconnected pores. Overall, the sample P-Ti20_55 provides a relatively load-bearable design with high cell affinity and is thus promising as a three-dimensional bio-scaffold.

Strontium Oxide Deposited onto a Load-Bearable and Porous Titanium Matrix as Dynamic and High-Surface-Contact-Area Catalysis for Transesterification

Strontium oxide (SrO) deposited onto a porous titanium (Ti)-based scaffold (P-Ti) is a promising and novel approach for high-throughput transesterification. Notably, a highly porous and calcinated scaffold provides a load-bearable support for a continuous process, while the calcinated SrO catalyst, as it is well distributed inside the porous matrix, can extend its surface contact area with the reactant. In this work, the formation of transesterification reaction with the conversion and production of olive oil to biodiesel inside the porous matrix is particularly examined. The as-designed SrO-coated porous titanium (Ti)-based scaffold with 55% porosity was prepared via a hydrothermal procedure, followed by a dip coating method. Mechanical tests of samples were conducted by a nanoindentator, whereas the physical and chemical structures were identified by IR and Raman Spectroscopies. The results implied that SrO catalysts can be firmly deposited onto a load-bearable, highly porous matrix and play an effective role for the transesterification reaction with the oil mass. It is promising to be employed as a load-bearable support for a continuous transesterification process, such as a process for batch or continuous biodiesel production, under an efficient heating source by a focused microwave system.

Specific Unbinding Forces Between Mutated Human P-Selectin Glycoprotein Ligand-1 and Viral Protein-1 Measured Using Force Spectroscopy

Protein tyrosine sulfation (PTS) is a key modulator of extracellular protein-protein interaction (PPI), which regulates principal biological processes. For example, the capsid protein VP1 of enterovirus 71 (EV71) specifically interacts with sulfated P-selectin glycoprotein ligand-1 (PSGL-1) to facilitate virus invasion. Currently available methods cannot be used to directly observe PTS-induced PPI. In this study, atomic force microscopy was used to measure the interaction between sulfated or mutated PSGL-1 and VP1. We found that the binding strength increased by 6.7-fold following PTS treatment on PSGL-1 with a specific antisulfotyrosine antibody. Similar results were obtained when the antisulfotyrosine antibody was replaced with the VP1 protein of EV71; however, the interaction forces of VP1 were only approximately one-third of those of the antisulfotyrosine antibody. We also found that PTS on the tyrosine-51 residue of glutathione S-transferases fusion-PSGL-1 was mainly responsible for the PTS-induced PPI. Our results contribute to the fundamental understanding of PPI regulated through PTS.

Ageing, Shocks and Wear Mechanisms in ZTA and the Long-Term Performance of Hip Joint Materials

The surface morphologies and microstructures of Zirconia Toughened Alumina (ZTA) femoral heads were analyzed following in vitro tests aiming to simulate in vivo degradation. Three phenomena potentially leading to degradation were investigated: shocks, friction and hydrothermal ageing. Shocks due to micro-separation created the main damage with the formation of wear stripes on the femoral head surfaces. Atomic Force Microscopy (AFM) images suggested the release of wear debris of various shapes and sizes through inter- and intra-granular cracks; some debris may have a size lower than 100 nm. A decrease in hardness and Young’s modulus was measured within the wear stripes by nanoindentation technique and was attributed to the presence of surface and sub-surface micro-cracks. Such micro-cracks mechanically triggered the zirconia phase transformation in those worn areas, which in return presumably reduced further crack propagation. In comparison with shocks, friction caused little wear degradation as observed from AFM images by scarce pullout of grains. The long-term resistance of the ZTA composite material against hydrothermal ageing is confirmed by the present observations.

Structure-dependent behaviours of skin layers studied by atomic force microscopy

The multilayer skin provides the physical resistance and strength against the environmental attacks, and consequently plays a significant role in maintaining the mammalian health. Currently, optical microscopy (OM) is the most common method for the research related to skin tissues while with the drawbacks including the possibility of changing the native morphology of the sample with the addition of the chemical or immunological staining and the restricted resolution of images for the direct observation of the tissue structures. To investigate if the function of each tissue is structure-dependent and the how the injured skin returns to the intact condition, we applied atomic force microscopy (AFM) on the sectioned mice-skin to reveal the tissue structures with a nanoscale resolution. From the outermost stratum to the inner layer of the skin tissue, the respectively laminated, fibrous, and brick-like structures were observed and corresponded to various functions. Due to the mechanical differences between the tissue constituents and their boundaries, the sizes and arrangements of the components were characterised and quantified by the mechanical mapping of AFM, which enabled the analytical comparisons between tissue layers. For the wound model, the skin tissues were examined with the initial formation of blood vessels and type-I collagen, which agreed with the stage of healing process estimated by OM but showed more detail information about the evolution of proteins among the skin. In conclusion, the characterisation of the components that consist of skin tissue by AFM enables the connection of the tissue function to the corresponded ultrastructure.

Enhancement of Wound Healing by Non-Thermal N2/Ar Micro-Plasma Exposure in Mice with Fractional-CO2-Laser-Induced Wounds

Micro-plasma is a possible alternative treatment for wound management. The effect of micro-plasma on wound healing depends on its composition and temperature. The authors previously developed a capillary-tube-based micro-plasma system that can generate micro-plasma with a high nitric oxide-containing species composition and mild working temperature. Here, the efficacy of micro-plasma treatment on wound healing in a laser-induced skin wound mouse model was investigated. A partial thickness wound was created in the back skin of each mouse and then treated with micro-plasma. Non-invasive methods, namely wound closure kinetics, optical coherence tomography (OCT), and laser Doppler scanning, were used to measure the healing efficiency in the wound area. Neo-tissue growth and the expressions of matrix metallopeptidase-3 (MMP-3) and laminin in the wound area were assessed using histological and immunohistochemistry (IHC) analysis. The results show that micro-plasma treatment promoted wound healing. Micro-plasma treatment significantly reduced the wound bed region. The OCT images and histological analysis indicates more pronounced tissue regrowth in the wound bed region after micro-plasma treatment. The laser Doppler images shows that micro-plasma treatment promoted blood flow in the wound bed region. The IHC results show that the level of laminin increased in the wound bed region after micro-plasma treatment, whereas the level of MMP-3 decreased. Based on these results, micro-plasma has potential to be used to promote the healing of skin wounds clinically.

Intense Raman scattering on hybrid Au/Ag nanoplatforms for the distinction of MMP-9-digested collagen type-I fiber detection

Well-ordered Au-nanorod arrays were fabricated using the focused ion beam method (denoted as fibAu_NR). Au or Ag nanoclusters (NCs) of various sizes and dimensions were then deposited on the fibAu_NR arrays using electron beam deposition to improve the surface-enhanced Raman scattering (SERS) effect, which was verified using a low concentration of crystal violet (10(-)(5)M) as the probe molecule. An enhancement factor of 6.92 × 10(8) was obtained for NCsfibAu_NR, which is attributed to the combination of intra-NC and NR localized surface plasmon resonance. When 4-aminobenzenethiol (4-ABT)-coated Au or Ag nanoparticles (NPs) were attached to NCsfibAu_NR, the small gaps between 4-ABT-coated NPs and intra-NCs allowed detection at the single-molecule level. Hotspots formed at the interfaces of NCs/NRs and NPs/NCs at a high density, producing a strong local electromagnetic effect. Raman spectra from as-prepared type I collagen (Col-I) and Ag-NP-coated Col-I fibers on NCsfibAu_NR were compared to determine the quantity of amino acids in their triple helix structure. Various concentrations of matrix-metalloproteinase-9-digested Col-I fibers on NCsfibAu_NR were qualitatively examined at a Raman laser wavelength of 785nm to determine the changes of amino acids in the Col-I fiber structure. The results can be used to monitor the growth of healing Col-I fibers in a micro-environment.

Capillary-tube-based micro-plasma system for disinfecting dental biofilm

PURPOSE

A low-temperature low-energy capillary-tube-based argon micro-plasma system was applied to disinfect Streptococcus mutans-containing biofilm.

MATERIALS AND METHODS

The micro-plasma system uses a hollow inner electrode that is ignited by a radio-frequency power supply with a matching network. The energy content was analyzed using optical emission spectroscopy. The micro-plasma-induced effect on a biofilm cultured for 24 or 48 h with a working distance of ≈3 mm at low temperature was evaluated. The morphologies of the treated live/dead bacteria and the produced polysaccharides after micro-plasma treatment were examined.

RESULTS

Scanning electron microscopy images and staining results show that most of the S. mutans on the treated biofilm were acutely damaged within a micro-plasma treatment time of 300 s.

CONCLUSIONS

The number of living bacteria underneath the treated biofilm greatly decreased with treatment time. The proposed micro-plasma system can thus disinfect S. mutans on/in biofilms.

Mouse prostate proteome changes induced by oral pentagalloylglucose treatment suggest targets for cancer chemoprevention

Recent in vitro and in vivo preclinical studies have suggested that the Oriental herbal compound penta-1, 2, 3, 4, 6-O-galloyl-beta-D-glucose (PGG) is a promising chemopreventive agent for prostate cancer. Little is known of its safety for chronic chemoprevention use and virtually nothing is known of its in vivo responsive proteins in the target organ. Here we treated male C57BL/6 mice with daily oral administration of PGG at two dosages (1 and 2 mg per mouse) from 7 to 14 weeks of age and profiled proteomic patterns in the prostate with iTRAQ labeling and 2D LC-MS/MS analyses. While neither dose affected feed intake and body weight gain, the 2 mg dose (∼80-100 mg per kg) led to a minor but statistically significant decrease of the weight of prostate and thymus. For proteomic profiling, five prostates were pooled from each group for protein extraction. Proteins were denatured, reduced, alkylated and digested to peptides. The peptides were labeled with iTRAQ reagents, mixed and subjected to 2D LC-MS/MS analyses. PGG consumption suppressed the abundance of oncoproteins (e.g., fatty acid synthase, clusterin) and up-regulated that of tumor suppressor proteins (e.g., glutathione S-transferase M), signifying changes that may contribute to prostate cancer risk reduction.

Conversion of emitted dimethyl sulfide into eco-friendly species using low-temperature atmospheric argon micro-plasma system

A custom-made atmospheric argon micro-plasma system was employed to dissociate dimethyl sulfide (DMS) into a non-foul-smelling species. The proposed system takes the advantages of low energy requirement and non-thermal process with a constant flow rate at ambient condition. In the experiments, the compositions of DMS/argon plasma, the residual gaseous phases, and solid precipitates were respectively characterized using an optical emission spectrometer, various gas-phase analyzers, and X-ray photoemission spectroscopy. For 400 ppm DMS introduced into argon plasma with two pairs of electrodes (90 W), a complete decomposition of DMS was achieved; the DMS became converted into excited species such as C, C(2), H, and CH. When gaseous products were taken away from the treatment area, the excited species tended to recombine and form stable compounds or species, which formed as solid particles and gaseous phases. The solid deposition was likely formed by the agglomeration of C-, H-, and S-containing species that became deposited on the quartz inner tube. For the residual gaseous phases, low-molecular-weight segments mostly recombined into relatively thermodynamic stable species, such as hydrogen, hydrogen sulfide, and carbon disulfide. The dissociation mechanism and treatment efficiency are discussed, and a treatment of converting DMS into H(2)-, CS(2)-, and H(2)S-dominant by-products is proposed.

Depth-sensing nano-indentation on a myelinated axon at various stages

A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.

Focused ion beam-fabricated Au micro/nanostructures used as a surface enhanced Raman scattering-active substrate for trace detection of molecules and influenza virus

The focused ion beam (FIB) technique was used to precisely fabricate patterned Au micro/nanostructures (fibAu). The effects of surface enhanced Raman scattering (SERS) on the fibAu samples were investigated by adjusting the geometrical, dimensional, and spacing factors. The SERS mechanism was evaluated using low-concentration rhodamine 6G (R6G) molecules, physically adsorbed or suspended on/within the micro/nanostructures. The results indicated that for detecting R6G molecules, hexagon-like micro/nanostructures induced a higher electromagnetic mechanism (EM) due to the availability of multiple edges and small curvature. By decreasing the dimensions from 300 to 150 nm, the laser-focused area contained an increasing number of micro/nanostructures and therefore intensified the excitation of SERS signals. Moreover, with an optimized geometry and dimensions of the micro/nanostructures, the relative intensity/surface area value reached a maximum as the spacing was 22 nm. An exponential decrease was found as the spacing was increased, which most probably resulted from the loss of EM. The spacing between the micro/nanostructures upon the fibAu was consequently regarded as the dominant factor for the detection of R6G molecules. By taking an optimized fibAu to detect low-concentration influenza virus, the amino acids from the outermost surface of the virus can be well distinguished through the SERS mechanism.

In vivo impedance evaluation of Au/PI microelectrode with surface modulated by alkanethiolate self-assembled monolayers

The goal of this study was to verify that a fully implanted microelectrode with modulated surface may have a reduced rising rate of total impedance and a longer life time. In the previous work, alkanethiolate self-assembled monolayers (SAMs) surface as protein-resistant spacer or cell-repulsive dense-packed spacer has been verified from in vitro experiments. In this study, microelectrodes with the same surface modulation were implanted into the subcutaneous layers of Wistar rats. Nine rats were implanted with the microelectrodes and the total impedance data were measured every 24 h for 2 weeks after implantation. An equivalent electrical circuit model of the electrode-tissue interface was established and parameters were estimated by using an optimization algorithm. Four out of nine rats had manifested acute inflammation reaction and the rests revealed only slight tissue response. Histological examination for the inflammatory group showed fibroblasts, macrophages, and polymorphonuclear leukocytes in adjacent to the electrode contact surface. In the inflammatory group, no significantly difference in total impedance was found in both types of electrodes. However, the trend of total impedance of SAMs-treated electrodes could maintain a steady state value after 1 week. For the non-inflammatory group, both types of electrodes could reduce the impedance value within implanted days. The tissue resistance might be related to the thickness of cells adhered upon the electrode contacts.

Continuous depth-sensing nano-mechanical characterization of living, fixed and dehydrated cells attached on a glass substrate

Continuous depth-sensing nano-indentation on living, fixed and dehydrated fibroblast cells was performed using a dynamic contact module and vertically measured from a pre-contact state to the glass substrate. The nano-indentation tip-on-cell approaches took advantage of finding a contact surface, followed by obtaining a continuous nano-mechanical profile along the nano-indentation depths. In the experiment, serial indentations from the leading edge, i.e., the lamellipodium to nucleus regions of living, fixed and dehydrated fibroblast cells were examined. Nano-indentations on a living cell anchored upon glass substrate were competent in finding the tip-on-cell contact surfaces and cell heights. For the result on the fixed and the dehydrated cells, cellular nano-mechanical properties were clearly characterized by continuous harmonic contact stiffness (HCS) measurements. The relations of HCS versus measured displacement, varied from the initial tip-on-cell contact to the glass substrate, were presumably divided into three stages, respectively induced by cellular intrinsic behavior, the substrate-dominant property, and the substrate property. This manifestation is beneficial to elucidate how the underlying substrate influences the interpretation of the nano-mechanical property of thin soft matter on a hard substrate. These findings, based upon continuous depth-sensing nano-indentations, are presumably valuable as a reference to related work, e.g., accomplished by atomic force microscopy.

Effects of cell concentration and collagen concentration on contraction kinetics and mechanical properties in a bone marrow stromal cell-collagen construct

A cell-collagen construct is commonly used to investigate the phenomenon of wound healing and to estimate the variables for tissue engineering. The purpose of this study was to assess the effects of cell concentration and collagen concentration on the contraction kinetics and mechanical properties of bone marrow stromal cell (BMSC) seeded collagen lattices. To investigate the effects of both variables on the contraction kinetics, the construct contraction was monitored up to 13 days. Incremental stress- relaxation tests were carried out after a 2-week incubation to obtain the stress-strain profiles, which were subsequently assessed in a quasilinear viscoelastic (QLV) model. During contraction, aligned BMSCs were observed first in the interior portion of the ring, followed by the middle portion and finally in the exterior portion. Constructs seeded with a higher initial cell concentration (higher than 1 x 10(5) cells/mL) or lower initial collagen concentration (lower than 2 mg/mL) exhibited faster contraction, higher ultimate stress, and superior elasticity and reduced relaxation behavior (p < 0.05). The cell-collagen model was successfully used to yield information regarding the initial cell concentration and the initial collagen concentration on contraction kinetics and mechanical behavior, which may have possible application in tissue engineering.

Ultra-thin phospholipid layers physically adsorbed upon glass characterized by nano-indentation at the surface contact level

Dipalmitoylphosphatic acid was chosen as a model to interpret how molecules physically adsorbed upon glass responded to an infinitesimal oscillation force at the surface contact level. Oscillation of a nano-indentation tip toward the phospholipid layers was driven by a dynamic contact module at a constant harmonic frequency; the phase angle of the oscillation frequency was exponentially relaxed along the nano-scale displacement. The tip-on-molecule contact was thereafter identified and influenced by the characteristic of the physically adsorbed phospholipids. By applying the harmonic displacement of the nano-indentation tip and making a distinction between full contact displacements, the thickness of the phospholipid layers was thereafter estimated. Moreover, the additional force required to penetrate through the physically adsorbed molecules was minor compared to the analogous process for the chemically adsorbed ones. The importance of recognizing the physically adsorbed molecules is relevant to applications of contact mechanics for the distinction of various phospholipids. Furthermore it is very promising to interpret the mechanism by which cells convert mechanical stimuli into biochemical responses on the channels of phospholipids.

Nano-indentation at the surface contact level: applying a harmonic frequency for measuring contact stiffness of self-assembled monolayers adsorbed on Au

In this study, the well-ordered alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths and tail groups were employed as examples for nano-characterization on their mechanical properties. A novel nano-indentation technique with a constant harmonic frequency was applied on SAMs chemically adsorbed on Au to explore their contact mechanics, and furthermore to interpret how SAM molecules respond to an infinitesimal oscillation force without pressing them. Experimental results demonstrated that the harmonic contact stiffness along with the measured displacement of SAMs/Au was distinguishable using a dynamic contact modulus with the distinct feature of phase angles. Phase angles resulted from the relaxing continuation of an applied harmonic frequency and mostly influenced by the outermost tail group of SAM molecules. The harmonic contact stiffness of SAM molecules obviously increased with the densely packed alkyl chains and relatively intense agglomeration of the head group at the anchoring site. As a consequence, the result of this work is relevant to contact mechanics at the surface contact level for the distinction of molecular substances attached on a solid surface. Furthermore it is particularly anticipated to identify biological molecules of variable qualities under a fluid-like micro-environment.

Characterization of surface modification on microelectrode arrays for in vitro cell culture

This study aims to investigate surface-modified microelectrodes on the microelectrode arrays (MEAs) for neuronal interfaces with in vitro cell culture. The polyimide (PI) MEA was fabricated by using micro-electro-mechanical systems (MEMS) techniques. Self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) were utilized to modify the microelectrode surface of the MEA. The SAMs' modified surface of microelectrodes offered a reliable interface to immobilize biological ligands through covalent bonding. To increase biocompatibility, the poly-D-lysine (PDL) was immobilized on the SAMs' modified microelectrodes. Several analytical techniques were used to define the physical structure and functional groups of surface-modified gold microelectrodes on the MEA. Spectra of the Fourier transform infrared reflection (FTIR) were applied to characterize the molecular structure of MUA-SAMs and PDL on the microelectrodes. The spectra, two peaks of amide I (at 1,613 cm(-1)) and amide II (at 1,548 cm(-1)), revealed that covalent amide bonding existed in PDL-MUA-SAMs modified surfaces. The thickness and formation of the MUA and PDL were also observed and quantified by using an atomic force microscope (AFM). The impedance measurement of PDL-MUA-SAMs modified MEA only increased slightly to an average of 524.6 +/- 55.8 kOmega from 352.9 +/- 34.4 kOmega of bare gold microelectrode (p < 0.05, N = 20). In addition, the time-course changes of total impedance resulting from cell sealing resistance and gap reactance were recorded for 7 days for inferring the growth of cell lines on the electrode contact of modified MEA. The experiment of 3T3 fibroblasts, PC12 cells, primary glial cells, and primary cortical neurons cultured on the modified MEAs displayed a good adhesion rate. These biocompatibility assays demonstrated that the neuronal cells are able to grow in a proximity to PDL-MUA-SAMs modified microelectrodes of the MEAs for effective electrophysiological stimulation/sensing schemes and for future implantation purposes.

Determination of the optimized conditions for coupling oligonucleotides with 16-mercaptohexadecanoic acid chemically adsorbed upon Au

A specific 5'-modified amino group oligonucleotide (Primer 1), 15-mers in length, is selectively coupled with the carboxyl terminated 16-mercaptohexadecanoic acid (MHDA) chemically adsorbed on Au and subsequently hybridized with Antisense Primer. The amide-coupling process is of significance to create an intermediate structure for the purpose of adding Primer 1, while the hybridization reaction is relevant to various diagnostic purposes to determine the presence in nucleic acids for a target sequence. In this work, the coupling setting was particularly emphasized by varying commonly used temperatures and pH values with a definite concentration of coupling agents (i.e., 10 mM). The recombination with analogous hybridization treatment was investigated using high resolution X-ray photoelectron spectroscopy and a 75 degrees grazing angle Fourier transform infrared spectrometer. On the basis of the spectroscopic studies, the optimized conditions for the coupling process that is also correlated with the molecular density of subsequent hybridization process on MHDA/Au have been proposed at 37 degrees C and a pH value of 4.5. Therefore, it is pertinent to intensify the joining of short-chain DNA strands by complementary base pairing in diagnostic applications such as the identification of single nucleotide polymorphisms.

Histological complexities of pancreatic lesions from transgenic mouse models are consistent with biological and morphological heterogeneity of human pancreatic cancer

Although pancreatic cancer is the fourth leading cause of cancer death, it has received much less attention compared to other malignancies. There are several transgenic animal models available for studies of pancreatic carcinogenesis, but most of them do not recapitulate, histologically, human pancreatic cancer. Here we review some detailed molecular complexity of human pancreatic cancer and their reflection in histomorphological complexities of pancreatic lesions developed in various transgenic mouse models with a special concern for studying the effects of chemotherapeutic and chemopreventive agents. These studies usually require a large number of animals that are at the same age and gender and should be either homozygote or heterozygote but not a mixture of both. Only single-transgene models can meet these special requirements, but many currently available models require a mouse to simultaneously bear several transgene alleles. Thus it is imperative to identify new gene promoters or enhancers that are specific for the ductal cells of the pancreas and are highly active in vivo so as to establish new single-transgene models that yield pancreatic ductal adenocarcinomas for chemotherapeutic and chemopreventive studies.

Modification of Monomolecular Self-Assembled Films by Nitrogen−Oxygen Plasma

The modification of octadecanethiolate self-assembled monolayers on Au and Ag by nitrogen-oxygen downstream microwave plasma with variable oxygen content (up to 1%) has been studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy. The primary processes were dehydrogenation, desorption of hydrocarbon and sulfur-containing species, and the oxidation of the alkyl matrix and headgroup-substrate interface. The exact character and the rates of the plasma-induced changes were found to be dependent on the substrate and plasma composition, with the processes in the aliphatic matrix and headgroup-substrate interface being mostly decoupled. In particular, the rates of all major plasma-induced processes were found to be directly proportional to the oxygen content in the plasma, which can be, thus, considered as a measure of the plasma reactivity. Along with the character of the observed changes, exhibiting a clear dominance of the oxidative processes, this suggests that the major effect of the oxygen-nitrogen downstream microwave plasma is provided by reactive oxygen-derived species in the downstream region, viz. long-living oxygen radicals and metastable species.

Cell adhesion and related phenomena on the surface-modified Au-deposited nerve microelectrode examined by total impedance measurement and cell detachment tests

This study investigated alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths adsorbed upon novel Au-coated microelectrodes, of which the surface properties were quantitatively evaluated by surface characterization and 3T3 fibroblast cell adhesion, total impedance and cell detachment tests. Thin-film SAMs adsorbed upon Au/PI/Si provided a hydrophobic or passive surface with increased water contact angle and initial total impedance. From cell adhesion tests, we can observe that the film formed as a dense-packed spacer resulted in incomplete cell sealing of 3T3 cells upon the surface-modified microelectrode. Thus the decrease in cell coverage rate and in the slope in association with total impedance as a function of cell-surface reaction time can be found. To study the adhesion force of a comparable single cell attached upon varied modified surfaces, a cell detachment test using a triangular probe tip of a well defined cantilever was carried out in medium containing fibroblast cells. Overall, both the peak force and the work required to detach a comparable single cell from the anchoring domain corresponded well to the increased length of alkyl chains adsorbed upon Au/PI/Si. Both measurements on the SAM modified surfaces demonstrated much smaller values than those on the pristine Au/PI/Si surface. These results concluded that a cell-repulsive characteristic was clearly formed on the SAM modified microelectrode surface. The non-adhering properties of surface-modified microelectrodes should provide better sensitivity for neuromuscular stimulation as well as for the recording of infinitesimal neural signals in future applications of neural prostheses.

Proteomic profiling of erythrocyte proteins by proteolytic digestion chip and identification using two-dimensional electrospray ionization tandem mass spectrometry

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition, and other interfacial phenomena. The bonding of enzyme to SAMs of alkanethiols onto gold surfaces is exploited to produce an enzyme chip. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent. A two-dimensional liquid-phase separation scheme coupled with mass spectrometry is presented for proteomic analysis of erythrocyte proteins. The application of proteomics, particularly with reference to analysis of proteins, will be described. Surface analyses have revealed that the X-ray Photoelectron Spectroscopy (XPS) C1s and N1s core levels illustrate the immobilization of trypsin. These data are also in good agreement with Fourier Transformed Infrared Reflection-Attenuated Total Reflection (FTIR-ATR) spectra for the peaks at Amide I and Amide II. Using two-dimensional nano-high performance liquid chromatography electrospray ionization tandem mass spectrometry (2D nano-HPLC-ESI-MS/MS) system observations, analytical results have demonstrated the erythrocyte proteins digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, it also shows the enzyme digestion ability of the immobilized trypsin. The experiment results revealed the identification of 272 proteins from erythrocyte protein sample. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Dual properties of the deacetylated sites in chitosan for molecular immobilization and biofunctional effects

Polypropylene nonwoven fabric was surface-activated by high-density oxygen microwave plasma, followed by graft copolymerization with acrylic acid (AAc) and then coupling with chitosan molecules. The pAAc-grafted surface containing C=O in carboxylic acid exhibited a hydrophilic character capable of promoting water absorbency. A larger portion of minimum 85% deacetylated sites in chitosan molecules was then coupled with the grafted pAAc (around 149 microg.cm(-2)) by forming amide bonds at their interface. The covalently bonded chitosan was weighted around 44 microg.cm(-2). The smaller portion of the deacetylated sites demonstrated a distinctive structure as polycations, i.e., NH(3)(+), on the immobilized chitosan. The respective structures following sequential reactions were identified using Fourier transform infrared-attenuated total reflection and X-ray photoelectron spectroscopy with peaks deconvolution. The NH(3)(+) sites on the immobilized chitosan exhibited biofunctional in anticoagulation and in antibacterial property. Blood cells agglutination or agglomeration upon the chitosan-immobilized surface, in particular for red blood cells and platelets, resulted from hydrophilic effect derived from the grafted pAAc and the chitosan itself, and ionic attractions between polycations and blood cells. In addition, the agglutinated cells retained their original morphologies. It is therefore very promising to apply this durable chitosan-immobilized surface for making an antibacterial support, at the same time, for retaining blood cell affinity.

Proteomic profiling of platelet proteins by trypsin immobilized self-assembled monolayers digestion chip and protein identification using electrospray ionization tandem mass spectrometry

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition, and other interfacial phenomena. Recently, the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling agent. Experimental results have revealed that the X-ray Photoelectron Spectroscopy (XPS) C1s core levels at 286.3 and 286.5 eV (C with N), 288.1 eV (amide bond), and 289.3 eV (carboxyl) illustrate the immobilization of trypsin. These data were also in good agreement with Fourier-Transformed Infrared Reflection-Attenuated Total Reflection (FTIR-ATR) spectra for the peaks valued at 1659.4 cm(-1) (amide I) and 1546.6 cm(-1) (amide II). Using electrospray ionization tandem mass spectrometry (ESI-MS/MS) observations, analytical results have demonstrated the platelet proteins digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, platelet proteins were digested on the trypsin-immobilized SAMs surface, which shows the enzyme digestion ability of the immobilized trypsin. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Characterization of trypsin immobilized on the functionable alkylthiolate self-assembled monolayers: a preliminary application for trypsin digestion chip on protein identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition and other interfacial phenomena. Recently the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N '-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent. The thickness of SAMs was determined by optical ellipsometer; contact angles of the modified Au surfaces were measured in air using a goniometer. The Second Harmony Generation data displays the last few percents of the alkylthiol molecules adsorbed and produced the complete monolayer by inducing the transition from a high number of gauche defects to an all-trans conformation. Using X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transformed Infrared Reflection-Absorption and Attenuated Total Reflection Spectroscopes (FTIR-RAS and ATR), we examined the chemical structures of samples with different treatments. By matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), we demonstrated the digestion of bovine serum albumin (BSA) on the trypsin-immobilized SAMs surface. Experimental results have revealed that the XPS C1s core levels at 286.3 and 286.5 eV (Amine bond), 288.1 eV (Amide bond) and 289.3 eV (Carboxylic acid) illustrate the immobilization of trypsin. These data were also in good agreement with FTIR-ATR spectra for the peaks valued at 1659.4 cm(-1) (Amide I) and 1546.6 cm(-1) (Amide II). Using MALDI-TOF MS observations, analytical results have demonstrated the BSA digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, BSA was digested on the trypsin-immobilized SAMs surface, which shows the enzyme digestion ability of the immobilized trypsin. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Alkanethiolate self-assembled monolayers as functional spacers to resist protein adsorption upon Au-coated nerve microelectrode

Alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths were adsorbed upon Au-coated nerve microelectrodes and employed as protein-resistant spacers. The microelectrode spiraled as a cuff type can be used for restoring motor function via electrical stimulation on the peripheral nerve system; however, an increase of electrode impedance might occur during implantation. In this work, a thin-film SAMs treatment upon Au/polyimide (PI) surface of the microelectrode provided a hydrophobic characteristic, which retarded protein adsorption at the initial stage and subsequent pileup (or thickening) process. The protein-resistant effect exhibited comparable SAMs of different chain lengths adsorbed upon Au/PI surfaces. The increase of electrode impedance as a function of protein deposition time was mainly correlated with the addition of reactance that was associated with the pileup thickness of the deposited protein. Particularly, the SAMs-modified surface was capable to detach a significant portion of the accumulated protein from the protein-deposited SAMs/Au/PI, whereas the protein-deposited layers exhibited firm adhesion upon Au/PI surface. It is therefore very promising to apply thin-film SAMs adsorbed upon Au-coated surface for bioinvasive devices that have the need of functional electrical stimulations or sensing nerve signals during chronic implantation.

Modification of aliphatic self-assembled monolayers by free-radical-dominant plasma: the role of the plasma composition

Modification of octadecanethiolate self-assembled monolayers on Au by nitrogen-oxygen or argon-oxygen downstream microwave plasma with a low oxygen content (estimated below several percent) has been studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy and water contact angle measurements. For both types of plasma, the primary processes were found to be the loss of conformational and orientational order and the oxidation of the alkyl matrix and headgroup-substrate interface. At the same time, the film modification occurred much faster and with different intermediates for the nitrogen plasma than for the argon plasma. The reasons for these differences are considered in terms of the different reactivities and different efficiencies of the energy transfer between the plasma constituents in these two types of plasma.

Surface properties and in vitro analyses of immobilized chitosan onto polypropylene non-woven fabric surface using antenna-coupling microwave plasma

Antenna coupling microwave plasma enables a highly efficient and oxidative treatment of the outermost surface of polypropylene (PP) non-woven fabric within a short time period. Subsequently, grafting copolymerization with acrylic acid (AAc) makes the plasma-treated fabric durably hydrophilic and excellent in water absorbency. With high grafting density and strong water affinity, the pAAc-grafted fabric greatly becomes feasible as an intensive absorbent and as a support to promote chitosan-immobilization through amide bonds. Experimental result demonstrated that surface analyses by FTIR-ATR have shown that R-CONH-R', amide binding were emerged between pAAc and chitosan. The XPS measurements on C(1s) 286.0 eV (C-OH), 286.5 eV (C-N) and 288.1 eV (O=C-NH) also could be found. Bioactivity assessments on the chitosan-immobilized surfaces were anticipated by activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen concentration. By means of cell counter we counted the ratio of blood cell adhesion on the modified fabric matrix. After human plasma incubated with the chitosan-immobilized PP fabrics, the required time for aPTT and blood cell adhesion increased significantly, while fibrinogen concentration and TT did not change. Due to the capability of anticoagulation and cell adhesion, the chitosan-immobilized PP fabric can be used as the substrate for cell culturing and then developed the wound-dressing substitute for second-degree burn.

The study of the sterilization effect of gamma ray irradiation of immobilized collagen polypropylene nonwoven fabric surfaces

Exposure to gamma ray irradiation is a frequent, clean, and superior method used to prevent bacterial contamination of sterilized biomedical end products. However, the potential damage induced by gamma ray irradiation of collagen is of concern because of the decay of bioactivity, which correlates with considerable structural alterations. In this experiment, antenna-coupling microwave plasma was utilized to activate nonwoven polypropylene (PP) fabric, and then the sample was grafted to acrylic acid (AAc). Type III collagen was immobilized by using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as a coupling agent. The collagen-immobilized samples, with temperatures of under 4 degrees C, were exposed to gamma ray irradiation at different dose intervals. Gamma ray irradiation was applied to evaluate the bioactivity on the collagen-immobilized nonwoven polypropylene and to determine the results of sterilization. Five kinds of sterilization index bacteria, all subject to Good Manufacturing Practice (GMP) criteria, were applied as a standard plate-count sterilization test. Our experimental results demonstrate that in human plasma incubated with various intervals of gamma ray irradiation, fibrinogen concentration decreases while platelet and red blood cell adhesion increase. However, the dose required for thrombination demonstrated a significant change in gamma ray irradiation exposure of fewer than 10 KGy (p = 0.05). The decay of bioactivity of the gamma-ray-irradiated collagen-bonded surfaces was evaluated and indicated that the decrease of R-CONHR', the degradation of amides ([broken bond]C[bond]N bonds of collagen and formation of the ROCNH(2) and O[double bond]CR' bonds), and the increase of C[bond]O, C[double bond]O bonds gradually may damage collagen by increasing the intervals of gamma ray irradiation. These effects considerably influence the bioactivity of the collagen-bonded fabric. It is clear that gamma ray irradiation exposure of approximately 10 KGy has the potential of moderating the bioactivities of collagen and therefore likely is a vital factor in the acceleration of biodegradation. The dose required for thrombination and sterilization reaches significance at 7.5 KGy.