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Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and Huntington’s disease represent some of the most prevalent neurodegenerative disorders afflicting millions of people worldwide. Unfortunately, there is a lack of efficacious treatments to cure or stop the progression of these disorders. While the causes of such a lack of therapies can be attributed to various reasons, the disappointing results of recent clinical trials suggest the need for novel and innovative approaches. Since its discovery, there has been a growing excitement around the potential for CRISPR-Cas9 mediated gene editing to identify novel mechanistic insights into disease pathogenesis and to mediate accurate gene therapy. To this end, the literature is rich with experiments aimed at generating novel models of these disorders and offering proof-of-concept studies in preclinical animal models validating the great potential and versatility of this gene-editing system. In this review, we provide an overview of how the CRISPR-Cas9 systems have been used in these neurodegenerative disorders.

An innovative approach to identify new conformational antigens of Aβ1–42 recognized by IgG autoantibodies as biomarkers of state and stage in Alzheimer’s disease (AD) patients is described. In particular, through the use of bioinformatics modeling, conformational similarities between several Aβ1–42 forms and other amyloid-like proteins with F1 capsular antigen (Caf1) of Yersinia pestis were first found. pVIII M13 phage display libraries were then screened against YPF19, anti-Caf1 monoclonal antibody, and IgGs of AD patients, in alternate biopanning cycles of a so-called “double binding” selection. From the selected phage clones, one, termed 12III1, was found to be able to prevent in vitro Aβ1–42-induced cytotoxicity in SH-SY5Y cells, as well as to promote disaggregation of preformed fibrils, to a greater extent with respect to wild-type phage (pC89). IgG levels detected by 12III1 provided a significant level of discrimination between diseased and nondemented subjects, as well as a good correlation with the state progression of the disease. These results give significant impact in AD state and stage diagnosis, paving the way for the development not only for an innovative blood diagnostic assay for AD precise diagnosis, progressive clinical assessment, and screening but also for new effective treatments.

Multiple myeloma (MM) is a malignant disease based on differentiated plasma cells (PCs) in the bone marrow (BM). Flow cytometry and fluorescence microscopy, used to identify a large combination of clusters of differentiation (CDs), are applied for MM immunophenotyping. However, due to the heterogeneous MM immunophenotypes, more antibody panels are necessary for a preliminary diagnosis and for the monitoring of minimal residual disease (MRD). In this study, we evaluated the use of phage clones as probes for the identification of several PCs immunophenotypes from MM patients. First, A 9-mer M13-pVIII phage display library was screened against an MM.1 cells line to identify peptides that selectively recognize MM.1 cells. Then, the most representative phage clones, with amino acid sequences of foreign peptides closer to the consensus, were labelled with isothiocyanate of fluorescein (FITC) and were used to obtain a fluorescent signal on cells in ex-vivo samples by fluorescence microscopy. Selected phage clones were able to discriminate different MM immunophenotypes from patients related to CD45, CD38, CD56, and CD138. Our results highlight the possibility of using a phage-fluorescence probe for the simultaneous examination of the presence/absence of CDs associated with disease usually detected by combination of anti-CD antibodies. The design of a multi-phage imaging panel could represent a highly sensitive approach for the rapid detection of immunophenotype subtypes and the subsequent characterization of patient disease status.

Sepsis is a systemic inflammatory response ensuing from presence and persistence of microorganisms in the bloodstream. The possibility to identify them at low concentrations may improve the problem of human health and therapeutic outcomes. So, sensitive and rapid diagnostic systems are essential to evaluate bacterial infections during the time, also reducing the cost. In this study, from random M13 phage display libraries, we selected phage clones that specifically bind surface of Staphyloccocus aureus, Pseudomonas aeruginosa and Escherichia coli. Then, commercial magnetic beads were functionalized with phage clones through covalent bond and used as capture and concentrating of pathogens from blood. We found that phage-magnetic beads complex represents a network which enables a cheap, high sensitive and specific detection of the bacteria involved in sepsis by micro-Raman spectroscopy. The enter process required 6 h and has the limit of detection of 10 Colony Forming Units on 7 ml of blood (CFU/7 ml).

The conformational variation of the viral capsid structure plays an essential role both for the environmental resistance and acid nuclear release during cellular infection. The aim of this study was to evaluate how capsid rearrangement in engineered phages of M13 protects viral DNA and peptide bonds from damage induced by UV-C radiation. From in silico 3D modelling analysis, two M13 engineered phage clones, namely P9b and 12III1, were chosen for (i) chemical features of amino acids sequences, (ii) rearrangements in the secondary structure of their pVIII proteins and (iii) in turn the interactions involved in phage capsid. Then, their resistance to UV-C radiation and hydrogen peroxide (H2O2) was compared to M13 wild-type vector (pC89) without peptide insert. Results showed that both the phage clones acquired an advantage against direct radiation damage, due to a reorganization of interactions in the capsid for an increase of H-bond and steric interactions. However, only P9b had an increase in resistance against H2O2. These results could help to understand the molecular mechanisms involved in the stability of new virus variants, also providing quick and necessary information to develop effective protocols in the virus inactivation for human activities, such as safety foods and animal-derived materials.

The presented work deals with the uptake of gold nanoparticles (Au NPs) by M13 phages in solutions. In particular, the Au NPs uptake modalities and their localization in the filamentous phages are evaluated and measured. Gold spherical nanoparticles (with an average diameter of the order of 10 nm) are obtained by laser ablation in water with a sodium citrated surfactant. The interest of such application comes from the possibility to employ living biological structures to transport heavy metallic nanoparticles inside cells of tumoral tissues. Indeed, phages have the capability to introduce Au NPs in the proximity to the cell nucleus, increasing the efficiency of DNA destruction in the tumoral cells by employing low doses of ionizing radiation during radiotherapy and hyperthermia treatments. Several analyses and microscopy characterizations of the prepared phages samples embedding gold nanoparticles are presented, demonstrating that the presence of Au NPs increases the phages imaging contrast.

The bacteria wall fulfills important physiological functions at the cell, depending on its composition and organization. Many researches focused their studies in understanding the change of its properties not only in strength and permeability, but also in morphological plasticity due to both chemical and physical stresses. In particular, filamentation morphology is a cryptic phenomenon, with involve for great variety of bacteria, which allow them to acquire adaptive benefits. This phenotypic alteration consists of an alteration or lack of cell septation during the cell growth, as consequence of DNA damage or development of stress, such as nutritional factors, antibiotic resistance, low temperature, non-availability of oxygen, high osmolarity, and antimicrobial agents. These cells result in modification of elongation 10-50 times, thickness, chemical composition, and extent of cross-linking of the cell wall polymers than normal-shaped cells. Moreover, the advancement in the morphology engineering permitted the manipulation of the genes encoding the proteins belonging to the plasma membrane or cytoplasm, to have the control over the bacterial shapes and of the its cytoplasmatic environment. In biotechnology application, the intracellular space is primary used for a greater accumulation of secondary products, such as polyhydroxyalkanoates (PHAs). This review provides an insight into environmental induction of filamentation morphology and its use in biotechnological process. KEY POINTS: • Environmental stresses inducing filamentation morphology • Morphology engineering in biotechnological processes • Increase of polyhydroxyalkanoates (PHAs) accumulation.

Foodborne pathogens are one of the main concerns in public health, which can have a serious impact on community health and health care systems. Contamination of foods by bacterial pathogens (such as Staphylococcus aureus, Streptococci, Legionella pneumophila, Escherichia coli, Campylobacter jejuni and Salmonella typhimurium) results in human infection. A typical example is the current issue with Coronavirus, which has the potential for foodborne transmission and ruling out such concerns is often difficult. Although, the possible dissemination of such viruses via the food chain has been raised. Standard bacterial detection methods require several hours or even days to obtain the results, and the delay may result in food poisoning to eventuate. Conventional biochemical and microbiological tests are expensive, complex, time-consuming and not always reliable. Therefore, there are urgent demands to develop simple, cheap, quick, sensitive, specific and reliable tests for the detection of these pathogens in foods. Recent advances in smart materials, nanomaterials and biomolecular modeling have been a quantum leap in the development of biosensors in overcoming the limitations of a conventional standard laboratory assay. This research aimed to critically review bacteriophage-based biosensors, used for the detection of foodborne pathogens, as well as their trends, outcomes and challenges are discussed. The future perspective in the use of simple and cheap biosensors is in the development of lab-on-chips, and its availability in every household to test the quality of their food.

Extremophiles are optimal models in experimentally addressing questions about the effects of cosmic radiation on biological systems. The resistance to high charge energy (HZE) particles, and helium (He) ions and iron (Fe) ions (LET at 2.2 and 200 keV/&micro, m, respectively, until 1000 Gy), of spores from two thermophiles, Bacillushorneckiae SBP3 and Bacilluslicheniformis T14, and two psychrotolerants, Bacillus sp. A34 and A43, was investigated. Spores survived He irradiation better, whereas they were more sensitive to Fe irradiation (until 500 Gy), with spores from thermophiles being more resistant to irradiations than psychrotolerants. The survived spores showed different germination kinetics, depending on the type/dose of irradiation and the germinant used. After exposure to He 1000 Gy, D-glucose increased the lag time of thermophilic spores and induced germination of psychrotolerants, whereas L-alanine and L-valine increased the germination efficiency, except alanine for A43. FTIR spectra showed important modifications to the structural components of spores after Fe irradiation at 250 Gy, which could explain the block in spore germination, whereas minor changes were observed after He radiation that could be related to the increased permeability of the inner membranes and alterations of receptor complex structures. Our results give new insights on HZE resistance of extremophiles that are useful in different contexts, including astrobiology.

Trusted methods for identifying different Multiple Myeloma (MM) cells and their biological diversity due to their immunophenotypic variety are often little detailed and difficult to find in literature. In this work, we show that micro-Raman spectroscopy can be used to highlight if there is a certain degree of distinction or correlation between the MM subtype plasmacells in relation to the cluster of differentiation (CD45+/CD38+/CD138-) and (CD45-/CD38+/CD138+). After taking samples from the bone marrow of patients with Multiple Myeloma, the PCs were sorted by flow cytometry, selecting the most common CD of the disease, i.e. CD 45, CD38 and CD138. Some spectral differences are observed comparing the Raman spectra of the two set of samples investigated. To better define in which spectral regions there are greater differences and, therefore, to which biological contributions the changes refers, we also explored the principal component analysis (PCA) of the collected Raman data. The spectral variations between the different sorted cells have been highlighted by plotting loading vectors PC1 and PC2, which shows a net differentiation between the two set of cells. Ultimately, the differences shown by PCA have been associated with the spectral variations observed and explained in terms of changes of proteins and lipid contributions. Thus, the differentiation of Multiple Myeloma subtype plasma cells by confocal micro-Raman spectroscopy can be proposed as a diagnostic tool in the speeding up of cell identification, assessing the intracellular biochemical changes that take place in cancer cells.

Staphylococcus aureus is a major human pathogen causing health care-associated and community-associated infections. Early diagnosis is essential to prevent disease progression and to reduce complications that can be serious. In this study, we selected, from a 9-mer phage peptide library, a phage clone displaying peptide capable of specific binding to S. aureus cell surface, namely St.au9IVS5 (sequence peptide RVRSAPSSS).The ability of the isolated phage clone to interact specifically with S. aureus and the efficacy of its bacteria-binding properties were established by using enzyme linked immune-sorbent assay (ELISA). We also demonstrated by Western blot analysis that the most reactive and selective phage peptide binds a 78KDa protein on the bacterial cell surface. Furthermore, we observed selectivity of phage-bacteria-binding allowing to identify clinical isolates of S. aureus in comparison with a panel of other bacterial species. In order to explore the possibility of realizing a selective bacteria biosensor device, based on immobilization of affinity-selected phage, we have studied the physisorbed phage deposition onto a mica surface. Atomic Force Microscopy (AFM) was used to determine the organization of phage on mica surface and then the binding performance of mica-physisorbed phage to bacterial target was evaluated during the time by fluorescent microscopy. The system is able to bind specifically about 50% of S. aureus cells after 15' and 90% after one hour. Due to specificity and rapidness, this biosensing strategy paves the way to the further development of new cheap biosensors to be used in developing countries, as lab-on-chip (LOC) to detect bacterial agents in clinical diagnostics applications.

Polyhydroxyalkanoates (PHAs) are considerable biopolymers that have gained an increasing biotechnological interest in different applications, although their industrial production presents several limitations. Filamentous bacterial cells could represent a possible strategy to increase PHA yield, since more abundant PHA inclusions can be stored in elongated than in rod-shaped cells. At first, we determined the optimal batch culture conditions to induce filamentation in Pseudomonas mediterranea CFBP-5447T, using glutamine, glycerol, glucose, and sodium octanoate, as the sole carbon source, at low- (100 rpm) or high- (250 rpm) shaking speeds. Successively, a fermentative process was set up using glutamine in a co-metabolic strategy with glycerol, and the PHAs production was compared in rod-shaped and filamentous cells. High glutamine concentrations (from 28 to 56 mM) were able to induce alone filamentation, whereas at lower glutamine concentrations (5-10 mM), the shaking speeds became critical to allow or not filamentous phenotype. PHA granule production was higher in filamentous than in rod-shaped cells, when glycerol (46.6 mM) was added to glutamine (5 mM) in co-metabolism, and fermentation was performed at a low-shaking speed. After extraction and precipitation, PHA yield was about two times higher in filamentous than that rod-shaped cells. Our results provide new insights into filament-inducing conditions and indicate a potential use of filamentous P. mediterranea CFBP-5447T cells to increase PHA yield. These findings could have great advantages in PHAs recovering during downstream processes, since the harvesting of elongated cells is much less time-consuming and energy expensive than required with rod-shaped cells.

New recognition probes sensible, specific and robust is one of the major problems of biosensor assay. Detection biosensors has utilized antibodies or enzymes as bioreceptors; however, these have numerous disadvantages of limited binding sites and physico-chemical instabilities, can negatively affect capture and detection of target in diagnostic device. In this contest, Phage-Display provides a valuable technique for obtaining large amounts of specific and robustness bio-probes in a relatively short time. This technique relies on the ability of M13 bacteriophages (or phages) to display specific and selective target-binding peptides on major coat protein pVIII of their surface. In this work, we used P9b phage clone, displaying a foreign peptide QRKLAAKLT to selectively recognize Pseudomonas aeruginosa like bioreceptor. We describe different methods of functionalization to realize a selective bacteria biosensor surfaces. Several surfaces, such as latex and magnetic beads and polymeric surfaces such as mica, APTES and PEI, were functionalized by covalent bonds or physisorption with P9b. The efficiency of the surface functionalization procedures was evaluated by ELISA and AFM, while capture efficiency of the anchored phages has been assessed by plate count and Fluorescence microscopy. The results of this work pave the way to the use of phages as bioreceptor.

Discovery of new markers for the identification and discrimination of cell types is one of the principal objectives in cancer diagnostics. In the last years, many researchers used phage-display technology in vitro and in vivo to obtain random peptide probes able to bind towards cancer targets to be used in diagnostic systems and new targeted drug. In this work, we proposed a Single Drop Biosensor based on phage-labelled probes to detect leukaemia cells in blood from patients affected by chronic lymphocytic leukaemia (CLL). Results show that phage-labelled probes were able to recognize lymphocytes and lymphoblastic cells both in leukemic peripheral blood mononuclear cells and in whole blood from patients affected by CLL. The “proof of concept” proposed, using the phage labelled as bio-probe, could be an alternative way to produce new biosensor for monitoring of chronic pathology. Furthermore the results may have translational relevance for identification and exploring of new ligands directed against cancer hematological cells.

Nowadays, novel less-expensive nanoformulations for in situ-controlled and safe delivery of photosensitisers (PSs) against opportunistic pathogens in body-infections areas need to be developed. Antimicrobial photodynamic therapy (aPDT) is a promising approach to treat bacterial infections that are recalcitrant to antibiotics. In this paper, we propose the design and characterization of a novel nanophototherapeutic based on the trade cyclodextrin CAPTISOL® (sulfobutylether-beta-cyclodextrin, SBE-βCD) and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphine tetrakis(p-toluenesulfonate) (TMPyP) to fabricate efficient biocompatible systems for aPDT. Spherical nanoassemblies of about 360 nm based on CAPTISOL®/TMPyP supramolecular complexes with 1:1 stoichiometry and apparent equilibrium binding constant (Kb ≅ 1.32 × 105 M−1) were prepared with entrapment efficiency of ≅ 100% by simple mixing in aqueous media and freeze-drying. These systems have been characterized by complementary spectroscopy and microscopy techniques. Time resolved fluorescence pointed out the strong interaction of porphyrin monomer within nanoassemblies (τ2 ≅ 11 ns with an amount of ca 90%) and scarce self-aggregation of porphyrins have been observed. Singlet oxygen comparative determination (ϕΔ CAPTISOL®/TMPyP = 0.58) assessed their photodynamic potential. Release and photostability studies have been carried out under physiological conditions pointing out the role of CAPTISOL® to sustain porphyrin release for more than 2 weeks and to protect PS from photodegradation. Finally, photoantimicrobial activity of nanoassemblies vs free porphyrin have been investigated against Gram-negative P. aeruginosa, E. coli and Gram-positive S. aureus. The proposed nanosystems were able to photokill both Gram-positive and -negative bacterial cells similarly to TMPyP at MBC90 = 6 µM of TMPyP and at 42 J/cm2 light dose. However, with respect to the less selective free TMPyP in biological sites, nanoassemblies exhibit sustained release properties and a higher photostability thus optimizing the PDT effect at the site of action. These results can open routes for in vivo translational studies on nano(photo)drugs and nanotheranostics based on less expensive formulations of CD and PS.

Pseudomonas aeruginosa and Staphylococcus aureus are two opportunistic human pathogens among the most common agents of nosocomial infections. The early detection plays an important role in health care, and pharmacological and biomedical sectors. The use of functional nanoparticles is promising candidate to create new materials and devices to improve diagnosis, prevention, and treatment of diseases in different fields of applications. In this work, we used phage-specific pVIII proteins, isolated from P9b and St.au9IVS5 phage clones, displaying exogenous peptide (QRKLAAKLT and RVRSAPSSS) to detect P. aeruginosa and S. aureus, respectively. These selective bioprobes were used in “one-step” functionalization of silicon nanoparticles (SiNPs) by pulsed laser ablation of silicon in an aqueous solution, containing phage-specific pVIII protein. The optical properties of the bioconjugates (pVIII–SiNPs) are examined by photoluminescence and UV–Vis spectroscopy. Furthermore, size distribution and ability of bioconjugates to bind its bacterial target has been investigated by scanning electron microscopy, scanning transmission electron microscopy, and epi-fluorescence microscope. Our results show that the bioconjugates are able to bind P. aeruginosa and S. aureus, respectively, within 30 min. Furthermore, the yellow–green photo-emissive properties, detected by epi-fluorescence microscopy, demonstrate their potential use as fluorescent probes silicon-based for in vitro applications.

A new type of coating, based on carboxylato-pillar[5]arene/poly(allylamine hydrochloride) multilayer films, for the sustained release of antibiotics with in vitro antiadhesive and antimicrobial activity against Gram-positive and Gram-negative bacteria is described.

Silicon nanoparticles (SiNPs) are widely used as promising nanoplatform owing to their high specific surface area, optical properties and biocompatibility. Silicon nanoparticles find possible application in biomedical environment for their potential quantum effects and the functionalization with biomaterials, too. In this work, we propose a new approach for bio-functionalization of SiNPs and M13-engineered bacteriophage, displaying specific peptides that selectively recognize peripheral blood mononuclear cells (PBMC). The “one-step” functionalization is conducted during the laser ablation of silicon plate in buffer solution with engineered bacteriophages, to obtain SiNPs binding bacteriophages (phage–SiNPs). The interaction between SiNPs and bacteriophage is investigated. Particularly, the optical and morphological characterizations of phage–SiNPs are performed by UV–Vis spectroscopy, scanning electron microscopy operating in transmission mode (STEM) and X-ray spectroscopy (EDX). The functionality of phage–SiNPs is investigated through the photoemissive properties in recognition test on PBMC. Our results showed that phage–SiNPs maintain the capability and the activity to bind PBMC within 30 min. The fluorescence of phage–SiNPs allowed to obtain an optical signal on cell type targets. Finally, the proposed strategy demonstrated its potential use in in vitro applications and could be exploited to realize an optical biosensor to detect a specific target.

The remarkable affinity of deca-carboxylatopillar[5]arene WP5 towards the aminoglycoside antibiotic, amikacin, in aqueous media is reported; in vitro studies on Gram-positive bacteria (Staphylococcus aureus) show that drug entrapment inside WP5 also takes place in the presence of the microrganisms, thus pointing to WP5 as an appealing carrier for amikacin targeted delivery.

A novel approach to impedance microbiology (IM) has been under investigation. In our approach, solution resistance variations will be generated from bacteriophage (phage) lyses of host cell and the consequent release of endoplasmic material. To sensitively detect the lysis, bacteria cells have to be concentrated in a micro-electrochemical cell so that dilution of the released conductive molecules will be minimised. Therefore, the detection principle has been developed in conjunction with a sample preparation method for bacteria capture and concentration based on phage functionalised paramagnetic nanobeads and magnetic concentration. Escherichia coli has been used as target bacteria and the beads have been functionalised with selective lytic phages. The method has a potential detection limit slightly below 10 CFU/chamber. The whole assay detection time is bound to be below 30 min as it is strictly linked to the phages lytic cycle. The assay has potential for integration in automated systems.

The early diagnosis of malignancy is the most critical factor for patient survival and the treatment of cancer. In particular, leukemic cells are highly heterogeneous, and there is a need to develop new rapid and accurate detection systems for early diagnosis and monitoring of minimal residual disease. This study reports the utilization of molecular networks consisting of entire bacteriophage structure, displaying specific peptides, directly assembled with silver nanoparticles as a new Surface Enhanced Raman Spectroscopy (SERS) probe for U937 cells identification in vitro. A 9-mer pVIII M13 phage display library is screened against U937 to identify peptides that selectively recognize these cells. Then, phage clone is assembled with silver nanoparticles and the resulting network is used to obtain a SERS signal on cell-type specific molecular targets. The proposed strategy could be a very sensitive tool for the design of biosensors for highly specific and selective identification of hematological cancer cells and for detection of minimal residual disease in a significant proportion of human blood malignancy. (C) 2015 Elsevier B.V. All rights reserved.

Conductivity modulated devices, similar to photoconductors in operation, for use as radiation detectors were fabricated from polycrystalline chemical vapor deposited diamond films. These detectors were designed to operate under extremely high radiation fields with a large dynamic range in both response and speed. Two types of detectors were studied: a parallel‐plate device and a surface device (SDT). The radiation used to excite these detectors was minimum ionizing electrons with an energy of 16 MeV and a nominal pulse width of less than 25 ps. The response time of all detectors was less than 45 ps. The sensitivity of the detectors was in the range 10−5–10−6 A/W. Over the operating range of the detectors, signal saturation was not observed because to the signal size was small in comparison to the applied bias voltage. The detectors appeared to be linear with dose and dose rate over two orders of magnitude, and for dose rates up to 1013 rad/s. Long‐lived signal decay tails contributed to much less than 1% ...

Phosphorus-doped diamond films were grown from CH 4 and H 2 using d.c. and microwave plasmas with PH 3 as the dopant source. The P incorporation which was quantified using secondary ion mass spectrometry varies by more than two orders of magnitude for a given ratio of PH 3 to CH 4 in the gas phase. The lowest incorporation occurs in single-crystal (homoepitaxial) layers and the highest occurs in the polycrystalline films with the smallest grain size, indicating that P incorporates preferentially at grain boundaries. Conductivities of approximately 10 −10 to 10 −9 Ω −1 cm −1 were measured at room temperature for P-doped films. Significant levels of Si and B impurities are unintentionally present in these films, which may compensate any potential donor behavior of P. The homoepitaxial films were characterized by high resolution X-ray diffraction. The peak widths at half-maximum for the (004) reflection for all films are comparable with that of the bare IIa natural diamond substrates (0.050°), regardless of thickness or doping, suggesting that the crystalline quality of the epitaxial layers is as good or better than that of the substrates.

Diamond radiation detectors have a lengthy history. Photoconductive UV detectors were developed in the 1920s and ionizing radiation detectors were created in the 1940s. However, these devices encountered restricted usage owing to the limitations of natural diamonds. Specifically, these limitations were the small size and lack of control of the material characteristics. Recent advances in the high quality growth of diamond by chemical vapor deposition have created the opportunity for the application of this material in practical detectors.

Homoepitaxial single-crystal diamond layers were grown on naturally occurring type Ia and IIa gemstone diamond substrates using microwave-plasma-assisted chemical vapor deposition techniques. The epitaxial layers ranged in thickness from 0.5 to 800 μm. Single crystals were grown both unintentionally doped and intentionally doped by means of gas phase dopants. Planar photoconductive diodes were fabricated from the high resistivity crystals and junction diodes were fabricated from the boron-doped crystal layers. The photoconductive diode response was measured and the output signals were analyzed to derive the carrier mobility and lifetime. Combined carrier photoconductive mobility values exceeded 3500 cm2 V−1s−1, only seen in the best IIa gemstone diamonds. Junction diodes yielded the highest breakdown fields with typical values in excess of 2 × 107 V cm−1 dielectric strength.

Significant improvements have been made over the last year in the quality of chemical vapor deposited (CVD) diamond films. In particular, efforts have been made to improve the mobilities and lifetimes of free carriers. Values as high as 4000 cm 2 per V-s have been measured for the combined electron and hole mobilities in the best polycrystalline diamond, which is comparable to that of the best single-crystal IIa natural diamonds. Comparable carrier lifetimes have also been observed, ranging from 150 ps to 1 ns in CVD diamond, compared with 100 to 600 ps in natural IIa diamonds. The films were produced by microwave-assisted CVD, and both polycrystalline and epitaxial films were studied. The carrier mobility and lifetime were measured using transient photoconductivity as a function of electric field and excitation density. Both velocity saturation and electron-hole scattering were observed in the CVD films, similar to behavior measured in natural diamonds. The drift distance at an electric field of 10 kV cm −1 was as high as 15 μm. The improved properties are most likely due to lowered defect densities. Comparable results between epitaxial and polycrystalline films suggest that structural defects may not be the limitation. The improved quality is a significant step toward the production of electronic devices made of diamond, in particular diamond detectors for ionizing radiation. Already CVD diamond has been used to detect ultraviolet light, X-rays and high energy charged particles.

We report a study of a defect responsible for the ‘‘g’’ bound exciton line at 1.5112 eV that is frequently detected in photoluminescence spectra of GaAs grown by molecular beam epitaxy (MBE). A direct correlation has been observed between this line and a transition at 1.4946 eV, which is shown to result from a conduction band‐to‐acceptor recombination involving a shallow, unidentified acceptorlike defect that is labeled ‘‘A.’’ The activation energy of the defect is 24.8±0.2 meV, about 1.7 meV lower than that of CAs acceptor. Upon hydrogenation the defect is passivated more extensively than any known shallow acceptor species in GaAs. This result is analyzed in terms of a passivation model, from which it can be inferred that the A defect is not due to a simple substitutional Group II impurity on a Ga site. Incorporation of the A defect strongly affects the luminescence properties of the material. An almost complete quenching of the donor‐bound exciton lines, profound changes in the line shape and relative i...

A series of boron‐doped polycrystalline diamond films grown by direct current and microwave plasma deposition was studied with Raman and infrared (IR) absorption spectroscopy. A Fano line shape is observed in the Raman spectra for films with a boron concentration in a narrow range near 1021 cm−3. The appearance of the Fano line shape is correlated with the disappearance of discrete electronic transitions of the boron acceptor observed in the IR spectrum and the shift of the broadened peak to lower energy. The Fano interaction is attributed to a quantum mechanical interference between the Raman phonon (0.165 eV) and transitions from the broadened impurity band to continuum states composed of excited acceptor and valence band states.

Phosphorus‐doped polycrystalline and homoepitaxial diamond films were grown using both microwave and dc plasma assisted chemical vapor deposition. P incorporation was quantified using secondary ion mass spectrometry, and was approximately ten times greater for polycrystalline films deposited using dc plasmas compared to microwave plasmas. For microwave‐assisted growth, P incorporation was approximately ten times greater in polycrystalline than homoepitaxial films. These effects appear to be due to preferential incorporation at grain boundaries, since higher levels of P are measured in samples with smaller grains. The films were highly electrically resistive, with conductivities of 10−10–10−9/Ω cm at room temperature.

The electrical characteristics of chemically vapor deposited (CVD) diamond films were measured as a function of film thickness. The samples studied were polycrystalline with the average grain size increasing from approximately 1 μm on the substrate side to approximately 30 μm on the growth surface for the thickest sample. Using time‐resolved transient photoconductivity and charged‐particle induced conductivity, the collection distance (d) that a free carrier drifts under the influence of an applied electric field was measured. Our data indicate that there is a gradient in the collection distance through the material. This gradient in electrical properties has implications for electronic uses of CVD diamond.

The discovery of new markers for the identification and discrimination of cell types such as neoplastic cells is one of the principal objectives in diagnostics. Using random M13 phage display libraries on the whole U937 cells, we selected a clone, named EIII6, displaying a peptide RKIVHAQTP that preferentially recognizes these cells. The human promonocytic cell line U937 is a model for leukemia, cancer therapeutics and in vitro hematopoietic cell differentiation. Therefore, we directly labeled the phage clone EIII6 with fluo rescein isothiocyanate (FITC) for microscopy imaging application. This method allowed to identify fixed U937 cells, while preserving binding affinity of labeled phage clones. Microscopic observations showed that U937 cells were fluorescently labeled. In order to further investigate the interaction between U937 cells and EIII6, we utilized Raman Spectroscopy. Spectral peaks observed at about 980, 1008, 1185, 1215, 1320,1340,1455, 1589 and 1660 cm- 1 , are commonly assignable to proteins, saccharides and lipids components of U937. These Raman peaks in U937-EIII6 complex are shifted in position or reduced in intensity when compared to U937 alone, suggesting that phage-probe were selectively localized at cell membrane. Thereafter, we realised networks consisting of EIII6 phage clone and Ag-Nanoparticles (AgNPs) as signal reporters in Surface Enhanced Raman Spectroscopy (SERS) to better discriminate U937 cells. With this approach, U937-EIII6 Raman spectral features become sharper and more intense, confirming the selective phage-cell interaction. Both methodological approaches, proposed in this work, allows to quickly and selectively identify U937 and could be extended to the identification of other types of neoplastic cells.

A high-quality, low-stress 200 gim epitaxial diamond film has been grown on a 400 μm thick high-temperature-high-pressure Ila diamond. X-ray diffraction images of the film indicate that a large region of the film is fairly defect free and individual dislocations have been imaged in this region. Depth-resolved Raman results indicate that the region of the film with a low density of defects also has lower stress than in the higher defect density region. Transient photoconductivity measurements were performed on the high and low line defect density regions of the homoepitaxial diamond film to determine the effects of the stress and defect density on the combined electron-hole mobility and carrier lifetime. The correlation between the electrical properties and the x-ray diffraction imaging suggests that line defects may not be the limiting factor in the carrier transport at the present film quality

A thick homoepitaxial CVD diamond film was grown on a large high temperature, high pressure (HTHP) Ha diamond to study the defects present in the CVD film. The HTHP diamond had dimensions of 6 mm x 6 mm x 0.44 mm. The thickness of the diamond was increased to 0.84 mm by microwave plasma CVD. X-ray topographs were taken before and after growth to compare the defects in CVD diamond to those in the HTHP diamond. Prior to growth the substrate was unstrained and the characteristic microstructure of stacking faults and dislocations was observed. There was also a surface relief, visible optically, on the substrate of lines along the [100] which are probably due to polishing. After deposition of the CVD film, the crystal was strained with the film in tension. The defect structure observed throughout the CVD film followed the surface relief of the substrate. Cathodoluminescence spectra indicate that the film contains nitrogen defect complexes which are not present in the substrate. Cathodoluminescence also indicates that there are more non-radiative recombination centers in the film than in the substrate. Electrical results from transient photoconductivity measurements indicate that while the mobilities of the film and the substrate are comparable, the lifetime is much shorter in the film, possibly reflecting the higher concentration of non-radiative recombination centers.

Advances in the deposition process have led to dramatic improvements in the electronic properties of polycrystalline diamond films produced by chemical vapor deposition (CVD). It is now possible to produce CVD diamond with properties approaching those of IIa natural diamonds. The combined electron-hole mobility, as measured by transient photoconductivity at low carrier density, is 4000 square centimeters per volt per second at an electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond and 300 picoseconds for single-crystal diamond. The collection distance at a field of 10 kilovolts per centimeter is 15 micrometers for the CVD diamond as compared to 30 micrometers for natural diamonds. The electrical qualities appear to correlate with the width of the diamond Raman peak. Also, although the collection distance at the highest fields in the films nearly equals the average grain size, there is no evidence of deleterious grain boundary effects.

The electrical properties associated with carrier mobility, μ, and lifetime, τ, have been investigated for the chemical vapor deposited (CVD) diamond films using charged particle-induced conductivity and time resolved transient photo-induced conductivity. The collection distance, d, the average distance which electron and hole depart when driven by an applied electric field E, was measured by both methods. The collection distance is related to the carrier mobility and lifetime by d = μEτ Our measurements show that the collection distance increases linearly with sample thickness for CVD diamond films. The collection distance at the growth side of the CVD diamond film is comparable to that of single crystal natural type IIa diamond; at the substrate side of the film, the collection distance is near zero. No saturation of the collection distance is observed for film thickness up to 500 microns.

Degradation in optical and electrical properties has been observed for high-purity and high-mobility p-type GaAs layers which contain significant concentrations of an unidentified shallow acceptor-like defect, labeled “A”, that is frequently incorporated in crystals grown by molecular beam epitaxy. Low-temperature photoluminescence and variable temperature Hall-effect measurements were employed to monitor the aging process in samples stored for about one year at room temperature. Profound changes in the exciton recombination spectra, indicative of increasing concentration of the “A” defect, have been accompanied by a decrease in hole mobility and an increase in carrier concentration. These results are discussed in the context of the acceptor-pair defect model, originally proposed by Eaves and Halliday [J. Phys. C: Solid State Phys. 17, L705 (1984)].

The incorporation of the Group IV impurities Si, Ge and C, as well as other defects, during MBE epitaxial growth of GaAs has been studied by photoluminescence, photothermal ionization spectroscopy, and variable temperature Hall effect measurements. Growth with constant Si doping flux but with different V/III flux ratios has shown that the sticking coefficient for Si under ordinary MBE growth conditions is not unity, but varies with the V/III flux ratio. The Si donor concentration increases substantially with increasing As 4 /Ga flux ratio, while the Si acceptor concentration remains nearly constant at less than 10 14 cm −3 . Thus, the commonly observed variation of carrier concentration with V/III ratio during Si doping is not due to the amphoteric behavior of Si, but is due to the variation with V/III ratio of the non-unity sticking coefficient of Si. This variation is explained by the kinetic effects associated with the surface reaction processes involved in Si impurity incorporation. The orientation dependence of the amphoteric behavior of Si, Ge and C has also been studied, and can be explained by different kinetic effects on the different orientations. The simple arguments concerning single or double dangling bonds and site availability as often worked, cannot explain the observed orientation dependence.

Electron‐paramagnetic‐resonance (EPR) studies demonstrate the presence of nitrogen point defects in microwave‐assisted chemical vapor deposition (CVD) diamond thin films. Polycrystalline powder pattern EPR spectra are interpreted with g=2.0023, A∥=114.0 MHz, and A⊥=81.3 MHz. These spin parameters are identical to those of nitrogen in single crystal natural diamonds. Quantitative EPR and secondary ion‐mass spectrometry (SIMS) results of CVD diamond thin films suggest that nitrogen point defect formation is favored over aggregate nitrogen formation.

Deep levels in high‐purity n‐type molecular beam epitaxy (MBE) GaAs and in undoped n‐type metalorganic chemical vapor deposition (MOCVD) GaAs samples annealed with various As overpressures were investigated using constant capacitance deep level transient spectroscopy on evaporated Au Schottky barrier diodes. Anomalous hole traps, which could be measured because of a surface effect, were observed in all annealed samples. EL2 traps were created in the MBE material by the annealing, while the concentration of EL2 in the annealed MOCVD material was about the same as that before annealing. The effect of annealing on the other electron traps in these samples is also studied and reported.

A shallow acceptor-like defect labeled “A” is frequently incorporated in molecular beam epitaxial GaAs. We report here anomalous photoluminescence effects that are induced by this defect. With increasing concentration of the “A” defect: (1) neutral and ionized donor-bound exciton peaks disappear almost completely even for donor concentration as high as 7×1014 cm-3 and compensation ratio ND/NA≈0.3; (2) a new, sharp line emerges at 1.5138 eV, and (3) the relative intensity and line shape of the free exciton transition change dramatically. These observations are discussed in the perspective of previous reports, where similar effects were, in our opinion, misinterpreted.

The current high level of interest in the growth of InP/InGaAsP/InGaAs lattice matched to InP, has influenced many researchers to consider the use of gas sources in growth by MBE. For gas flows greater than a few sccm, pumping speed requirements dictate the use of turbomolecular or diffusion pumps. GaAs samples with higher p-type mobilities than previously reported have been grown with a diffusion pumped molecular beam epitaxial system. This demonstration of the inherent cleanliness of a properly designed diffusion pumping system indicates that a diffusion pump is an excellent inexpensive and reliable choice for growth by molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.