Differential effects of the lipidic and ionic microenvironment on NPP1's phosphohydrolase and phosphodiesterase activities.

Ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) is an enzyme present in matrix vesicles (MV). NPP1 participates on the regulation of bone formation by producing pyrophosphate (PPi) from adenosine triphosphate (ATP). Here, we have used liposomes bearing dipalmitoylphosphatidylcholine (DPPC), sphingomyelin (SM), and cholesterol (Chol) harboring NPP1 to mimic the composition of MV lipid rafts to investigate ionic and lipidic influence on NPP1 activity and mineral propagation. Atomic force microscopy (AFM) revealed that DPPC-liposomes had spherical and smooth surface. The presence of SM and Chol elicited rough and smooth surface, respectively. NPP1 insertion produced protrusions in all the liposome surface. Maximum phosphodiesterase activity emerged at 0.082 M ionic strength, whereas maximum phosphomonohydrolase activity arose at low ionic strength. Phosphoserine-Calcium Phosphate Complex (PS-CPLX) and amorphous calcium-phosphate (ACP) induced mineral propagation in DPPC- and DPPC:SM-liposomes and in DPPC:Chol-liposomes, respectively. Mineral characterization revealed the presence of bands assigned to HAp in the mineral propagated by NPP1 harbored in DPPC-liposomes without nucleators or in DPPC:Chol-liposomes with ACP nucleators. These data show that studying how the ionic and lipidic environment affects NPP1 properties is important, especially for HAp obtained under controlled conditions in vitro.

Strontium-driven physiological to pathological transition of bone-like architecture: A dose-dependent investigation.

Whilst strontium (Sr2+) is widely investigated for treating osteoporosis, it is also related to mineralization disorders such as rickets and osteomalacia. In order to clarify the physiological and pathological effects of Sr2+ on bone biomineralization , we performed a dose-dependent investigation in bone components using a 3D scaffold that displays the hallmark features of bone tissue in terms of composition (osteoblast, collagen, carbonated apatite) and architecture (mineralized collagen fibrils hierarchically assembled into a twisted plywood geometry). As the level of Sr2+ is increased from physiological-like to excess, both the mineral and the collagen fibrils assembly are destabilized, leading to a drop in the Young modulus, with strong implications on pre-osteoblastic cell proliferation. Furthermore, the microstructural and mechanical changes reported here correlate with that observed in bone-weakening disorders induced by Sr2+ accumulation, which may clarify the paradoxical effects of Sr2+ in bone mineralization. More generally, our results provide physicochemical insights into the possible effects of inorganic ions on the assembly of bone extracellular matrix and may contribute to the design of safer therapies for treating osteoporosis. STATEMENT OF SIGNIFICANCE: Physiological-like (10% Sr2+) and excess accumulation-like (50% Sr2+) doses of Sr2+ are investigated in 3D biomimetic assemblies possessing the high degree of organization found in the extracellular of bone. Above the physiological dose, the organic and inorganic components of the bone-like scaffold are destabilized, resulting in impaired cellular activity, which correlates with bone-weakening disorders induced by Sr2+.

Seizures and epilepsy associated with central nervous system tuberculosis.

Central nervous system (CNS) tuberculosis is a life-threatening condition that usually presents with seizures, particularly in children and HIV-infected patients. Tuberculous meningitis (TBM) and tuberculomas are the two forms of CNS tuberculosis that can present with seizures. Seizures usually resolve after successful treatment of the underlying infection. However, the success of the treatment is usually based on an early diagnosis. Delay in the treatment of CNS tuberculosis increases the risk of its associated complications, such as stroke. This would lead to the development of epilepsy. Early seizures may be related to meningeal irritation and cerebral edema, whereas late seizures are often associated with structural brain lesions that generally require more advanced and prolonged treatment. Risk factors associated with the development of epilepsy include young age, refractory seizures, tuberculoma, cortical involvement, epileptiform discharges, and residual lesions. Treatment of CNS tuberculosis is based on early initiation of appropriate anti-tuberculous drugs, antiseizure medications, and correction of associated predisposing factors. Finally, further research into the mechanisms of seizures and the development of epilepsy in CNS tuberculosis could help improve management of these conditions.

Fungal Communities of the Pine Wilt Disease Complex: Studying the Interaction of Ophiostomatales With Bursaphelenchus xylophilus.

Considered one of the most devastating plant-parasitic nematodes worldwide, Bursaphelenchus xylophilus (commonly known as pinewood nematode, PWN) is the causal agent of the pine wilt disease in the Eurasian coniferous forests. This migratory parasitic nematode is carried by an insect vector (Monochamus spp.) into the host tree (Pinus species), where it can feed on parenchymal cells and reproduce massively, resulting in the tree wilting. In declining trees, PWN populations are strongly dependent on fungal communities colonizing the host (predominantly ophiostomatoid fungi known to cause sapwood blue-staining, the blue-stain fungi), which not only influence their development and life cycle but also the number of individuals carried by the insect vector into a new host. Our main aim is to understand if PWN-associated mycobiota plays a key role in the development of PWD, in interaction with the PWN and the insect vector, and to what extent it can be targeted to disrupt the disease cycle. For this purpose, we characterized the fungal communities of Pinus pinaster trees infected and non-infected with PWN in three collection sites in Continental Portugal with different PWD temporal incidences. Our results showed that non-infected P. pinaster mycoflora is more diverse (in terms of abundance and fungal richness) than PWN-infected pine trees in the most recent PWD foci, as opposed to the fungal communities of long-term PWD history sites. Then, due to their ecological importance for PWN survival, representatives of the main ophiostomatoid fungi isolated (Ophiostoma, Leptographium, and Graphilbum) were characterized for their adaptative response to temperature, competition in-between taxa, and as food source for PWN. Under the conditions studied, Leptographium isolates showed promising results for PWN control. They could outcompete the other species, especially O. ips, and significantly reduce the development of PWN populations when compared to Botrytis cinerea (routinely used for PWN lab culturing), suggesting this to be a natural antagonist not only for the other blue-stain species but also for the PWN.

Insights into the Role of Fungi in Pine Wilt Disease.

Pine wilt disease (PWD) is a complex disease that severely affects the biodiversity and economy of Eurasian coniferous forests. Three factors are described as the main elements of the disease: the pinewood nematode (PWN) Bursaphelenchus xylophilus, the insect-vector Monochamus spp., and the host tree, mainly Pinus spp. Nonetheless, other microbial interactors have also been considered. The study of mycoflora in PWD dates back the late seventies. Culturomic studies have revealed diverse fungal communities associated with all PWD key players, composed frequently of saprophytic fungi (i.e., Aspergillus, Fusarium, Trichoderma) but also of necrotrophic pathogens associated with bark beetles, such as ophiostomatoid or blue-stain fungi. In particular, the ophiostomatoid fungi often recovered from wilted pine trees or insect pupal chambers/tunnels, are considered crucial for nematode multiplication and distribution in the host tree. Naturally occurring mycoflora, reported as possible biocontrol agents of the nematode, are also discussed in this review. This review discloses the contrasting effects of fungal communities in PWD and highlights promising fungal species as sources of PWD biocontrol in the framework of sustainable pest management actions.

Guillain-Barré Syndrome Outbreak in Peru 2019 Associated With Campylobacter jejuni Infection.

OBJECTIVE: To identify the clinical phenotypes and infectious triggers in the 2019 Peruvian Guillain-Barré syndrome (GBS) outbreak. METHODS: We prospectively collected clinical and neurophysiologic data of patients with GBS admitted to a tertiary hospital in Lima, Peru, between May and August 2019. Molecular, immunologic, and microbiological methods were used to identify causative infectious agents. Sera from 41 controls were compared with cases for antibodies to Campylobacter jejuni and gangliosides. Genomic analysis was performed on 4 C jejuni isolates. RESULTS: The 49 included patients had a median age of 44 years (interquartile range [IQR] 30-54 years), and 28 (57%) were male. Thirty-two (65%) had symptoms of a preceding infection: 24 (49%) diarrhea and 13 (27%) upper respiratory tract infection. The median time between infectious to neurologic symptoms was 3 days (IQR 2-9 days). Eighty percent had a pure motor form of GBS, 21 (43%) had the axonal electrophysiologic subtype, and 18% the demyelinating subtype. Evidence of recent C jejuni infection was found in 28/43 (65%). No evidence of recent arbovirus infection was found. Twenty-three cases vs 11 controls (OR 3.3, confidence interval [CI] 95% 1.2-9.2, p < 0.01) had IgM and/or IgA antibodies against C jejuni. Anti-GM1:phosphatidylserine and/or anti-GT1a:GM1 heteromeric complex antibodies were strongly positive in cases (92.9% sensitivity and 68.3% specificity). Genomic analysis showed that the C jejuni strains were closely related and had the Asn51 polymorphism at cstII gene. CONCLUSIONS: Our study indicates that the 2019 Peruvian GBS outbreak was associated with C jejuni infection and that the C jejuni strains linked to GBS circulate widely in different parts of the world.

Manipulation of cutaneous leishmaniasis lesions: case series in a peruvian hospital. / Manipulación de lesiones en pacientes con leishmaniasis cutánea: serie de casos en un hospital peruano.

In cutaneous leishmaniasis endemic areas it is a common practice for patients to manipulate their lesions with traditional treatments as a first therapeutic option. A case series study was conducted in order to describe the frequency and the variations of the patient manipulation of cutaneous leishmaniasis lesions at the Cayetano Heredia Hospital. The study included 124 patients with cutaneous leishmaniasis. From the patient population it was found that 54% (67/124) manipulated their lesions. Of this, 92.5% (62/67) did so with chemicals, and 43.3% (29/67) with plants. The most frequent local changes reported by patients were increased lesion size in 35.8% (24/67) and increased inflammation in 28.4% (19/67). Manipulation by patients decreased the positivity of the parasitological diagnosis in those patients with ulcerative lesions.

En áreas endémicas de leishmaniasis cutánea es común que los pacientes manipulen sus lesiones con tratamientos tradicionales como primera opción terapéutica. Con el objetivo de describir la frecuencia y los cambios de la manipulación de lesiones de leishmaniasis cutánea de pacientes en el Hospital Cayetano Heredia, se realizó un estudio tipo serie de casos. Se incluyeron 124 pacientes con leishmaniasis cutánea. El 54% (67/124) manipuló sus lesiones; el 92,5% (62/67) lo hizo con productos químicos, y el 43,3% (29/67), con plantas. Los cambios locales más frecuentemente reportados por los pacientes fueron aumento de tamaño de la lesión en el 35,8% (24/67) e incremento de inflamación en el 28,4% (19/67). La manipulación disminuyó la positividad del diagnóstico parasitológico en aquellos pacientes con lesiones ulcerativas.

Strontium Calcium Phosphate Nanotubes as Bioinspired Building Blocks for Bone Regeneration.

Calcium phosphate (CaP)-based ceramics are the most investigated materials for bone repairing and regeneration. However, the clinical performance of commercial ceramics is still far from that of the native tissue, which remains as the gold standard. Thus, reproducing the structural architecture and composition of bone matrix should trigger biomimetic response in synthetic materials. Here, we propose an innovative strategy based on the use of track-etched membranes as physical confinement to produce collagen-free strontium-substituted CaP nanotubes that tend to mimic the building block of bone, i.e., the mineralized collagen fibrils. A combination of high-resolution microscopic and spectroscopic techniques revealed the underlying mechanisms driving the nanotube formation. Under confinement, poorly crystalline apatite platelets assembled into tubes that resembled the mineralized collagen fibrils in terms of diameter and structure of bioapatite. Furthermore, the synergetic effect of Sr2+ and confinement gave rise to the stabilization of amorphous strontium CaP nanotubes. The nanotubes were tested in long-term culture of osteoblasts, supporting their maturation and mineralization without eliciting any cytotoxicity. Sr2+ released from the particles reduced the differentiation and activity of osteoclasts in a Sr2+ concentration-dependent manner. Their bioactivity was evaluated in a serum-like solution, showing that the particles spatially guided the biomimetic remineralization. Further, these effects were achieved at strikingly low concentrations of Sr2+ that is crucial to avoid side effects. Overall, these results open simple and promising pathways to develop a new generation of CaP multifunctional ceramics that are active in tissue regeneration and able to simultaneously induce biomimetic remineralization and control the imbalanced osteoclast activity responsible for bone density loss.

Manipulación de lesiones en pacientes con leishmaniasis cutánea: serie de casos en un hospital peruano / Manipulation of cutaneous leishmaniasis lesions: case series in a peruvian hospital

RESUMEN En áreas endémicas de leishmaniasis cutánea es común que los pacientes manipulen sus lesiones con tratamientos tradicionales como primera opción terapéutica. Con el objetivo de describir la frecuencia y los cambios de la manipulación de lesiones de leishmaniasis cutánea de pacientes en el Hospital Cayetano Heredia, se realizó un estudio tipo serie de casos. Se incluyeron 124 pacientes con leishmaniasis cutánea. El 54% (67/124) manipuló sus lesiones; el 92,5% (62/67) lo hizo con productos químicos, y el 43,3% (29/67), con plantas. Los cambios locales más frecuentemente reportados por los pacientes fueron aumento de tamaño de la lesión en el 35,8% (24/67) e incremento de inflamación en el 28,4% (19/67). La manipulación disminuyó la positividad del diagnóstico parasitológico en aquellos pacientes con lesiones ulcerativas.

ABSTRACT In cutaneous leishmaniasis endemic areas it is a common practice for patients to manipulate their lesions with traditional treatments as a first therapeutic option. A case series study was conducted in order to describe the frequency and the variations of the patient manipulation of cutaneous leishmaniasis lesions at the Cayetano Heredia Hospital. The study included 124 patients with cutaneous leishmaniasis. From the patient population it was found that 54% (67/124) manipulated their lesions. Of this, 92.5% (62/67) did so with chemicals, and 43.3% (29/67) with plants. The most frequent local changes reported by patients were increased lesion size in 35.8% (24/67) and increased inflammation in 28.4% (19/67). Manipulation by patients decreased the positivity of the parasitological diagnosis in those patients with ulcerative lesions.

Clinical significance of anti-NMDAR concurrent with glial or neuronal surface antibodies.

OBJECTIVE: To determine the frequency and significance of concurrent glial (glial-Ab) or neuronal-surface (NS-Ab) antibodies in patients with anti-NMDA receptor (NMDAR) encephalitis. METHODS: Patients were identified during initial routine screening of a cohort (C1) of 646 patients consecutively diagnosed with anti-NMDAR encephalitis and another cohort (C2) of 200 patients systematically rescreened. Antibodies were determined with rat brain immunostaining and cell-based assays. RESULTS: Concurrent antibodies were identified in 42 patients (4% from C1 and 7.5% from C2): 30 (71%) with glial-Ab and 12 (29%) with NS-Ab. Glial-Ab included myelin oligodendrocyte glycoprotein (MOG) (57%), glial fibrillary acidic protein (GFAP) (33%), and aquaporin 4 (AQP4) (10%). NS-Ab included AMPA receptor (AMPAR) (50%), GABAa receptor (GABAaR) (42%), and GABAb receptor (8%). In 39 (95%) of 41 patients, concurrent antibodies were detected in CSF, and in 17 (41%), concurrent antibodies were undetectable in serum. On routine clinical-immunologic studies, the presence of MOG-Ab and AQP4-Ab was suggested by previous episodes of encephalitis or demyelinating disorders (8, 27%), current clinical-radiologic features (e.g., optic neuritis, white matter changes), or standard rat brain immunohistochemistry (e.g., AQP4 reactivity). GFAP-Ab did not associate with distinct clinical-radiologic features. NS-Ab were suggested by MRI findings (e.g., medial temporal lobe changes [AMPAR-Ab], or multifocal cortico-subcortical abnormalities [GABAaR-Ab]), uncommon comorbid conditions (e.g., recent herpesvirus encephalitis), atypical tumors (e.g., breast cancer, neuroblastoma), or rat brain immunostaining. Patients with NS-Ab were less likely to have substantial recovery than those with glial-Ab (5 of 10 [50%] vs 17 of 19 [89%], p = 0.03). CONCLUSIONS: Between 4% and 7.5% of patients with anti-NMDAR encephalitis have concurrent glial-Ab or NS-Ab. Some of these antibodies (MOG-Ab, AQP4-Ab, NS-Ab) confer additional clinical-radiologic features and may influence prognosis.

Formation of stable strontium-rich amorphous calcium phosphate: Possible effects on bone mineral.

Bone, tooth enamel, and dentin accumulate Sr2+, a natural trace element in the human body. Sr2+ comes from dietary and environmental sources and is thought to play a key role in osteoporosis treatments. However, the underlying impacts of Sr2+on bone mineralization remain unclear and the use of synthetic apatites (which are structurally different from bone mineral) and non-physiological conditions have led to contradictory results. Here, we report on the formation of a new Sr2+-rich and stable amorphous calcium phosphate phase, Sr(ACP). Relying on a bioinspired pathway, a series of Sr2+ substituted hydroxyapatite (HA) that combines the major bone mineral features is depicted as model to investigate how this phase forms and Sr2+ affects bone. In addition, by means of a comprehensive investigation the biomineralization pathway of Sr2+ bearing HA is described showing that not more than 10 at% of Sr2+, i.e. a physiological limit incorporated in bone, can be incorporated into HA without phase segregation. A combination of 31P and 1H solid state NMR, energy electron loss spectromicroscopy, transmission electron microscopy, electron diffraction, and Raman spectroscopy shows that Sr2+ introduces disorder in the HA culminating with the unexpected Sr(ACP), which co-exists with the HA under physiological conditions. These results suggest that heterogeneous Sr2+ distribution in bone is associated with regions of low structural organization. Going further, such observations give clues from the physicochemical standpoint to understand the defects in bone formation induced by high Sr2+ doses. STATEMENT OF SIGNIFICANCE: Understanding the role played by Sr2+ has a relevant impact in physiological biomineralization and provides insights for its use as osteoporosis treatments. Previous studies inspired by the bone remodelling pathway led to the formation of biomimetic HA in terms of composition, structures and properties in water. Herein, by investigating different atomic percentage of Sr2+ related to Ca2+ in the synthesis, we demonstrate that 10% of Sr2+ is the critical loads into the biomimetic HA phase; similarly to bone. Unexpectedly, using higher amount leads to the formation of a stable Sr2+-rich amorphous calcium phosphate phase that may high-dose related pathologies. Our results provide further understanding of the different ways Sr2+ impacts bone.

Is alkaline phosphatase biomimeticaly immobilized on titanium able to propagate the biomineralization process?

Tissue-nonspecific alkaline phosphatase (TNAP) is a key enzyme in the biomineralization process as it produces phosphate from a number of phospho-substrates stimulating mineralization while it also inactivates inorganic pyrophosphate, a potent mineralization inhibitor. We have previously reported on the reconstitution of TNAP on Langmuir monolayers as well as proteoliposomes. In the present study, thin films composed of dimyristoylphosphatidic acid (DMPA) were deposited on titanium supports by the Langmuir-Blodgett (LB) technique, and we determined preservation of TNAP's phosphohydrolytic activity after incorporation into the LB films. Increased mineralization was observed after exposing the supports containing the DMPA:TNAP LB films to solutions of phospho-substrates, thus evidencing the role of TNAP on the growth of calcium phosphates after immobilization. These coatings deposited on metallic supports can be potentially applied as osteoconductive materials, aiming at the optimization of bone-substitutes integration in vivo.

Synthesis of Sr-morin complex and its in vitro response: decrease in osteoclast differentiation while sustaining osteoblast mineralization ability.

Strontium ranelate (SrR) has been used as the ultimate choice for osteoporosis treatment. However, the development of more tolerable and bioactive Sr2+ carriers is still a need. The design of Sr2+-based platforms has moved towards the obtention of anion carriers that can also exhibit a positive effect on bone metabolism. In this sense, we used morin, a natural flavonoid, as a new arrangement for Sr2+ carriage in the synthesis of an Sr2+ complex. It has been claimed that phenolic compounds promote bone health. Therefore, we hypothesized that the association of Sr2+ with morin could improve its anabolic effects. Complexes with the general formula [(C15H9O7)Sr(H2O)2]Cl·3H2O were synthesized and characterized by elemental analysis, thermogravimetry, UV-Vis and infrared absorption spectroscopies and 1H-nuclear magnetic resonance. We showed that the complexation between morin and Sr2+ occurred among the 3-OH and 4C[double bond, length as m-dash]O groups of morin. Preosteoclasts cultures with the Sr-morin complex exhibited a reduced osteoclast differentiation rate and sustained osteoblast mineralization ability. The response of Sr-morin was higher than that observed for SrR at the same concentration range. Considering the above-mentioned observations, the Sr-morin complex could be an interesting approach to be further exploited not only as an alternative treatment for osteoporosis but also in the design of materials for faster osteointegration.

Different compact hybrid Langmuir-Blodgett-film coatings modify biomineralization and the ability of osteoblasts to grow.

Calcium phosphates (CaPs) are biomaterials widely used in tissue regeneration with outstanding biological performance. Although the tremendous improvements achieved in CaP's materials research over the years, their interaction with physiological environments still need to be fully understood. The aim of this study is to explore a biomimetic Langmuir-Blodgett (LB) membrane to template the growth of hydroxyapatite (HAp) coatings on Ti surfaces and the ability of these coatings in inducing biomineralization by osteoblasts cultured in vitro. Changing the phospholipids (i.e., dihexadecyl phosphate (DHP) or octadecylphosphonic acid (OPA)), we also tuned the surface Ca2+ concentration. This structural feature gave rise to different LB-hybrid surfaces where the concentration of Ca2+ in the OPA/HAp was higher than the concentration of Ca2+ in DHP/HAp coating. The higher Ca2+ amount on OPA/HAp coatings, allied to the physical-chemical features, lead to different responses on osteoblasts, stimulating or inhibiting the natural biomineralization. The OPA/HAp coating caused a delay in the osteoblast proliferation as indicated by the decrease in the cell viability at the 7th culture day. Improved cell differentiation triggered by the DHP/HAp coating resulted in higher osteoblast biomineralization. The present data underscore that besides both coatings being composed by HAp, the final interfacial composition and physical-chemical properties influence differently the osteoblast behavior. Although the best osteoblast's viability was found to OPA/HAp, our dataset attested that DHP/HAp induced mineralization more effectively than that. This unexpected finding highlight the importance of deeply understanding the biomaterial interface and suggest a promising approach to the design of biofunctional LB-based coatings with tunable properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2524-2534, 2018.

The role played by modified bioinspired surfaces in interfacial properties of biomaterials.

The success of a biomaterial relies on an appropriate interaction between the surface of that biomaterial and the surrounding environment; more specifically, the success of a biomaterial depends on how fluids, proteins, and cells interact with the foreign material. For this reason, the surface properties of biomaterial, such as composition, charge, wettability, and roughness, must be optimized for a desired application to be achieved. In this review we highlight different bioinspired approaches that are used to manipulate and fine-tune the interfacial properties of biomaterials. Inspired by noteworthy natural processes, researchers have developed materials with a functional anatomy that range from hierarchical hybrid structures to self-cleaning interfaces. In this review we focus on (1) the creation of particles and modified surfaces inspired by the structure and composition of biogenic mineralized tissues, (2) the development of biofunctional coatings, (3) materials inspired by biomembranes and proteins, and (4) the design of superwettable materials. Our intention is to point out different bioinspired methodologies that have been used to design materials for biomedical applications and to discuss how interfacial properties modified by manipulation of these materials determine their final biological response. Our objective is to present future research directions and to highlight the potential of bioinspired materials. We hope this review will provide an understanding of the interplay between interfacial properties and biological response so that successful biomaterials can be achieved.

Biomedical applications of nanotechnology.

The ability to investigate substances at the molecular level has boosted the search for materials with outstanding properties for use in medicine. The application of these novel materials has generated the new research field of nanobiotechnology, which plays a central role in disease diagnosis, drug design and delivery, and implants. In this review, we provide an overview of the use of metallic and metal oxide nanoparticles, carbon-nanotubes, liposomes, and nanopatterned flat surfaces for specific biomedical applications. The chemical and physical properties of the surface of these materials allow their use in diagnosis, biosensing and bioimaging devices, drug delivery systems, and bone substitute implants. The toxicology of these particles is also discussed in the light of a new field referred to as nanotoxicology that studies the surface effects emerging from nanostructured materials.

Biomimetic collagen/phospholipid coatings improve formation of hydroxyapatite nanoparticles on titanium.

Osseointegration between the surface of a certain material and the host tissue helps to evaluate the potential use of biomaterials in bone replacement. The physicochemical properties and biochemical composition of the material's surface regulates osseointegration. This study investigates how collagen into biomimetic matrixes affects hydroxyapatite (HAp) growth. Collagen was inserted into insoluble Langmuir monolayers containing either 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) or octadecylphosphonic acid (OPA) and transferred to titanium (Ti) supports by means of the Langmuir-Blodgett (LB) technique. The resulting films served as matrixes for HAp growth upon exposure of Ti discs to SBF. Scanning electron microscopy, atomic force microscopy, vibrational spectroscopy in the infrared region, X-ray diffraction, and energy dispersive X-ray spectroscopy aided characterization of the samples. Properties such as wettability, roughness, and surface free energy were also studied. The biocompatibility of the samples was investigated by osteoblast viability assays in vitro. Collagen interacted with DPPC and OPA at the air/water interface as evidenced by the pressure surface isotherms and the compressional modulus. Moreover, collagen in the subphase increased the stability of the phospholipid monolayer at high organization degree. Collagen incorporation into DPPC LB films induced formation of biomimetic HAp nanoparticles that resembled the HAp nanoparticles found in natural bone. Enhanced cell proliferation on the modified-Ti surfaces demonstrated that the coatings were not toxic to osteoblasts. These materials are potential candidates for bone-replacement applications.

Pendant-drop method coupled to ultraviolet-visible spectroscopy: A useful tool to investigate interfacial phenomena.

UV-vis spectroscopy is a powerful tool to investigate surface phenomena. Surface tension measurements coupled to spectroscopic techniques can help to elucidate how the interface organization influences the electronic properties of molecules. However, appreciable sample volumes are usually necessary to achieve strong signals during conduction of experiments. This study reports on the simultaneous acquisition of surface tension data and UV-vis spectra by axisymmetric drop shape analysis (ADSA) coupled to diffuse reflectance (DRUV) spectrophotometry using a pendant microliter-drop that requires small sample volumes and low analyte concentrations. Three example systems gave evidence of the applicability of this technique: (a) disaggregation of an organic dye driven by surfactant as a function of the surface tension and alterations in the UV-vis spectra, (b) activity of a glycosylphosphatidylinositol anchored enzyme estimated from formation of a colored product, and (c) interaction between this enzyme and biomimetic membrane systems consisting of dipalmitoylphosphaditylcholine and cholestenone. Apart from using smaller sample volume, this coupled technique allowed to investigate interfacial organization in the light of electronic spectra obtained in loco within a shorter acquisition time. This procedure provided precise interfacial information about static and dynamic systems. This has been the first study describing the kinetic activity of an enzyme in the presence of phospholipid monolayers through simultaneous determination of the surface tension and UV-vis spectra.

CdTe quantum dots as fluorescent probes to study transferrin receptors in glioblastoma cells.

BACKGROUND: Overexpression of transferrin receptors (TfRs), which are responsible for the intracellular uptake of ferric transferrin (Tf), has been described in various cancers. Although molecular biology methods allow the identification of different types of receptors in cancer cells, they do not provide features about TfRs internalization, quantification and distribution on cell surface. This information can, however, be accessed by fluorescence techniques. In this work, the quantum dots (QDs)' unique properties were explored to strengthen our understanding of TfRs in cancer cells. METHODS: QDs were conjugated to Tf by covalent coupling and QDs-(Tf) bioconjugates were applied to quantify and evaluate the distribution of TfRs in two human glioblastoma cells lines, U87 and DBTRG-05MG, and also in HeLa cells by using flow cytometry and confocal microscopy. RESULTS: HeLa and DBTRG-05MG cells showed practically the same TfR labeling profile by QDs-(Tf), while U87 cells were less labeled by bioconjugates. Furthermore, inhibition studies demonstrated that QDs-(Tf) were able to label cells with high specificity. CONCLUSIONS: HeLa and DBTRG-05MG cells presented a similar and a higher amount of TfR than U87 cells. Moreover, DBTRG-05MG cells are more efficient in recycling the TfR than the other two cells types. GENERAL SIGNIFICANCE: This is the first study about TfRs in human glioblastoma cells using QDs. This new fluorescent tool can contribute to our understanding of the cancer cell biology and can help in the development of new therapies targeting these receptors.

Formation of carrageenan-CaCO3 bioactive membranes.

The high biocompatibility and resorbability of polymeric membranes have encouraged their use to manufacture medical devices. Here, we report on the preparation of membranes consisting of carrageenan, a naturally occurring sulfated polysaccharide that forms helical structures in the presence of calcium ions. We incorporated CaCO3 particles into the membranes to enhance their bioactivity and mechanical properties. Infrared spectroscopy and X-ray diffraction data confirmed CaCO3 incorporation into the polymeric matrix. We tested the bioactivity of the samples by immersing them in a solution that mimics the ionic composition and pH of the human body fluid. The hybrid membranes generated hydroxyapatite, as attested by X-ray diffraction data. Scanning electron and atomic force microscopies aided investigation of membrane topography before and after CaCO3 deposition. The wettability and surface free energy, evaluated by contact angle measures, increased in the presence of CaCO3 particles. These parameters are important for membrane implantation in the body. Moreover, membrane stiffness was up to 110% higher in the presence of the inorganic particles, as revealed by Young's modulus.