Novel nanostructured lipid carriers loading Apigenin for anterior segment ocular pathologies.

Dry eye disease (DED) is a chronic multifactorial disorder of the ocular surface caused by tear film dysfunction and constitutes one of the most common ocular conditions worldwide. However, its treatment remains unsatisfactory. While artificial tears are commonly used to moisturize the ocular surface, they do not address the underlying causes of DED. Apigenin (APG) is a natural product with anti-inflammatory properties, but its low solubility and bioavailability limit its efficacy. Therefore, a novel formulation of APG loaded into biodegradable and biocompatible nanoparticles (APG-NLC) was developed to overcome the restricted APG stability, improve its therapeutic efficacy, and prolong its retention time on the ocular surface by extending its release. APG-NLC optimization, characterization, biopharmaceutical properties and therapeutic efficacy were evaluated. The optimized APG-NLC exhibited an average particle size below 200 nm, a positive surface charge, and an encapsulation efficiency over 99 %. APG-NLC exhibited sustained release of APG, and stability studies demonstrated that the formulation retained its integrity for over 25 months. In vitro and in vivo ocular tolerance studies indicated that APG-NLC did not cause any irritation, rendering them suitable for ocular topical administration. Furthermore, APG-NLC showed non-toxicity in an epithelial corneal cell line and exhibited fast cell internalization. Therapeutic benefits were demonstrated using an in vivo model of DED, where APG-NLC effectively reversed DED by reducing ocular surface cellular damage and increasing tear volume. Anti-inflammatory assays in vivo also showcased its potential to treat and prevent ocular inflammation, particularly relevant in DED patients. Hence, APG-NLC represent a promising system for the treatment and prevention of DED and its associated inflammation.

Development of a controlled-environment assay to induce iron deficiency chlorosis in soybean by adjusting calcium carbonates, pH, and nodulation.

BACKGROUND: Soybean iron deficiency chlorosis (IDC) is an important nutrient stress frequently found in high pH and/or soils high in calcium carbonates. To advance the understanding of IDC resistance in soybean, a rapid (21-day) controlled-environment assay was developed to investigate the effects of nodulation, pH, and calcium carbonate levels on soybean iron deficiency traits. This system was tested on four genotypes known to exhibit differences in iron efficiency, including two standard IDC check cultivars and a pair of near-isogenic lines exhibiting variation at an IDC resistance quantitative trait locus. Visual score, chlorophyll content, plant height, root dry mass, and shoot dry mass were measured to quantify iron stress. RESULTS: Calcium carbonate levels and nodulation were found to have the greatest effects on IDC severity. Increasing calcium carbonate levels worsened IDC symptoms, while nodulation reduced symptoms in all genotypes. Higher pH levels increased iron deficiency symptoms in check genotypes 'Corsoy 79' and 'Dawson', but did not induce iron deficiency symptoms in near-isogenic lines. A significant interaction was observed between genotype, nodulation, and calcium carbonate level, indicating that a specific treatment level could discern IDC symptoms between genotypes differing in resistance to IDC. CONCLUSIONS: IDC symptoms were successfully induced in the Check Genotypes Experiment as well as the NIL Experiment, indicating the success of using this assay for inducing IDC in controlled environments. However, our results suggest that treatment levels that best differentiate genotypes for their IDC resistance may need to be determined for each experiment because of the unique way in which different genotypes display symptoms and respond to iron deficiency conditions.

[Failure mode effect analysis for safety improvement in the automatic drug dispensing systems]. / Aplicación de un análisis modal de fallos y efectos para la mejora de la seguridad en la utilización de los sistemas automatizados de dispensación de medicamentos.

OBJECTIVE: To identify the risks in automated dispensing cabinet use in order to improve routine procedure safety. METHODS: We used the Failure Mode Effect Analysis (FMEA) methodology. A multidisciplinary team identified potential failure modes of the procedure through a brainstorming session. We assessed the impact associated with each failure mode with the Risk Priority Number (RPN), which involves three variables: occurrence, severity, and detectability. Improvement measures were established for failure modes with RPN>100 considered critical. The final RPN (theoretical) that would result from the proposed measures was also calculated. RESULTS: The process was divided into five sub-processes: automatic delivery of order replacement, to prepare order in a pyramidal cart, transport of the pyramidal cart from the pharmacy service to the automated dispensing cabinet, replacement of the automated dispensing cabinet by the pharmacy technician and dispensing/returning by nursing staff. Twenty-two failure modes, with 25 cases and with varying effects (severity 2-8) were evaluated. The sub-process with more failure modes with NPR>100 was dispensing/returning by nursing staff. CONCLUSIONS: The FMEA methodology was a useful tool when applied to automated dispensing cabinet system use. The implementation of improvement actions significantly reduced the risk.

The role of check dams in retaining organic carbon and nutrients. A study case in the Sierra de Ávila mountain range (Central Spain).

Soil organic carbon plays an important role in the global carbon cycle, accounting for 70% of the Earth's carbon. However, soil erosion can have a major impact on the stocks of soil carbon and other soil nutrients, such as nitrogen and phosphorous. Soil and water conservation techniques, such as the building of check dams, are usually employed to control sediment yields and the losses of other soil components. The aim of this research is thus to quantify the soil organic carbon (SOC), soil nitrogen (SN) and soil phosphorous (SP) retained by the check dams of a hydrologic and forest restoration project in the Sierra de Ávila mountain range (Ávila, Central Spain). Soil samples were taken from the sediment wedges of 30 check dams and from 30 native soils. Soil texture, electric conductivity, pH, C, N and P were measured in all the soil samples. The volume of sediment retained by the check dams was calculated by the Sections Method, which is very accurate in estimating the real volume of the sediment wedges. The total sediment yield in the area was thus estimated at 6.40 Mg·ha-1·yr-1 and the mean SOC, SN and SP densities were respectively 13.76, 0.48 and 0.05 kg·m-2. These findings thus are very reliable and allow us to conclude that check dams constitute an important instrument for controlling losses of SOC, SN and SP, and preventing these substances from passing into watercourses downstream of the area.

Multiplex polymerase chain reaction in combination with gel electrophoresis-inductively coupled plasma mass spectrometry: A powerful tool for the determination of gene copy number variations and gene expression changes.

During the last few years multiplex real-time or quantitative polymerase chain reaction PCR (qPCR) has become the method of choice for multiplex gene expression changes and gene copy number variations (CNVs) analysis. However, such determinations require the use of different fluorescent labels for the different amplified sequences, which increases significantly the costs of the analysis and limits the applicability of the technique for simultaneous amplification of many targets of interest in a single reaction. In this regard, the use of the coupling between gel electrophoresis (GE) separation with inductively coupled plasma mass spectrometry (ICP-MS) detection allows the label-free determination of multiplex PCR-amplified sequences (amplicons) by monitoring the P present in the DNA backbone. The quantitative dimension is obtained since under optimal and controlled multiplex PCR conditions the peak areas of the separated amplicons are directly proportional to the amount of DNA template in the original sample. Moreover, the calibration of the GE-ICP-MS system with a DNA ladder permits direct estimation of the size (bp) of the PCR products. The suitability of the proposed multiplex strategy has been evaluated addressing two different situations: determination of CNVs and gene expression changes in human ovarian cancer cells. In the first case, the results obtained for the simultaneous quantitation of CNVs of four genes (HER2, CCNE1, GSTM1, ACTB) on DNA obtained from OVCAR-3 cells were in accordance with the literature data, and also with the results obtained by conventional simplex qPCR. In the second case, multiplex gene expression changes of BAX, ERCC1 and CTR1 genes, using ACTB as constitutive gene, on A2780cis respect to A2780 cells, resistant and sensitive to cisplatin, respectively, provided the same information as single reaction reverse transcription (RT)-qPCR.

Enhanced case management can be delivered for patients with EVD in Africa: Experience from a UK military Ebola treatment centre in Sierra Leone.

BACKGROUND: Limited data exist describing supportive care management, laboratory abnormalities and outcomes in patients with Ebola virus disease (EVD) in West Africa. We report data which constitute the first description of the provision of enhanced EVD case management protocols in a West African setting. METHODS: Demographic, clinical and laboratory data were collected by retrospective review of clinical and laboratory records of patients with confirmed EVD admitted between 5 November 2014 and 30 June 2015. RESULTS: A total of 44 EVD patients were admitted (median age 37 years (range 17-63), 32/44 healthcare workers), and excluding those evacuated, the case fatality rate was 49% (95% CI 33%-65%). No pregnant women were admitted. At admission 9/44 had stage 1 disease (fever and constitutional symptoms only), 12/44 had stage 2 disease (presence of diarrhoea and/or vomiting) and 23/44 had stage 3 disease (presence of diarrhoea and/or vomiting with organ failure), with case fatality rates of 11% (95% CI 1%-58%), 27% (95% CI 6%-61%), and 70% (95% CI 47%-87%) respectively (p = 0.009). Haemorrhage occurred in 17/41 (41%) patients. The majority (21/40) of patients had hypokalaemia with hyperkalaemia occurring in 12/40 patients. Acute kidney injury (AKI) occurred in 20/40 patients, with 14/20 (70%, 95% CI 46%-88%) dying, compared to 5/20 (25%, 95% CI 9%-49%) dying who did not have AKI (p = 0.01). Ebola virus (EBOV) PCR cycle threshold value at baseline was mean 20.3 (SD 4.3) in fatal cases and 24.8 (SD 5.5) in survivors (p = 0.007). Mean national early warning score (NEWS) at admission was 5.5 (SD 4.4) in fatal cases and 3.0 (SD 1.9) in survivors (p = 0.02). Central venous catheters were placed in 37/41 patients and intravenous fluid administered to 40/41 patients (median duration of 5 days). Faecal management systems were inserted in 21/41 patients, urinary catheters placed in 27/41 and blood component therapy administered to 20/41 patients. CONCLUSIONS: EVD is commonly associated life-threatening electrolyte imbalance and organ dysfunction. We believe that the enhanced levels of protocolized care, scale and range of medical interventions we report, offer a blueprint for the future management of EVD in resource-limited settings.

Lipid nanoparticles (SLN, NLC): Overcoming the anatomical and physiological barriers of the eye - Part I - Barriers and determining factors in ocular delivery.

Ocular drug delivery is still a challenge for researchers in the field of pharmaceutical technology due to anatomical and physiological eye characteristics. The tissue barriers (such as cornea, conjunctiva, blood aqueous barrier, and blood-retinal barrier) limit the access of drugs to their targets. Taking into account the short retention time in the precorneal area of classical ocular dosage forms (e.g. solutions, suspensions or ointments) which are rapidly eliminated by tears and eyelid movement, only less than five percent of the administered drug attains intraocular structures. With the aim to overcome ocular barriers, drug delivery systems, able to increase ocular bioavailability reducing side effects, are recognized as promising alternative. In this review, the main barriers and strategies to increase drug transport in ocular delivery are comprehensively discussed, highlighting the factors involved in ocular transport of SLN and NLC.

Lipid nanoparticles (SLN, NLC): Overcoming the anatomical and physiological barriers of the eye - Part II - Ocular drug-loaded lipid nanoparticles.

In the recent decades, various controlled delivery systems have been introduced with the aim to improve solubility, stability and bioavailability of poorly absorbed drugs. Among all, lipid nanoparticles gather interesting properties as drug or gene delivery carriers. These systems, composed either of solid lipids (SLN) or of solid and liquid lipids (NLC) stabilized with surfactants, combine the advantages of other colloidal particles such as polymeric nanoparticles, fat emulsions and liposomes avoiding their main disadvantages. Lipid nanoparticles represent an interesting approach for eye drug delivery as they can improve the corneal absorption of drugs enhancing their bioavailability. The Generally Recognized as Safe status of formulation excipients, the scaling-up facilities and the possibility of sterilization, make them suitable for industrial production. In this review, the latest findings, potential applications, and challenges related to the use of lipid nanoparticles for ocular drug delivery are comprehensively discussed.

PEGylated PLGA nanospheres optimized by design of experiments for ocular administration of dexibuprofen-in vitro, ex vivo and in vivo characterization.

Dexibuprofen-loaded PEGylated PLGA nanospheres have been developed to improve the biopharmaceutical profile of the anti-inflammatory drug for ocular administration. Dexibuprofen is the active enantiomer of ibuprofen and therefore lower doses may be applied to achieve the same therapeutic level. According to this, two batches of nanospheres of different drug concentrations, 0.5 and 1.0mg/ml respectively, have been developed (the latter corresponding to the therapeutic ibuprofen concentration for inflammatory eye diseases). Both batches were composed of negatively charged nanospheres (--14.1 and --15.9mV), with a mean particle size below 200nm, and a high encapsulation efficiency (99%). X-ray, FTIR, and DSC analyses confirmed that the drug was dispersed inside the matrix of the nanospheres. While the in vitro release profile was sustained up to 12h, the ex vivo corneal and scleral permeation profile demonstrated higher drug retention and permeation in the corneal tissue rather than in the sclera. These results were also confirmed by the quantification of dexibuprofen in ocular tissues after the in vivo administration of drug-loaded nanospheres. Cell viability studies confirmed that PEGylated-PLGA nanospheres were less cytotoxic than free dexibuprofen in the majority of the tested concentrations. Ocular in vitro (HET-CAM test) and in vivo (Draize test) tolerance assays demonstrated the non-irritant character of both nanosphere batches. In vivo anti-inflammatory effects were evaluated in albino rabbits before and after inflammation induction. Both batches confirmed to be effective to treat and prevent ocular inflammation.

[Visitation policy, design and comfort in Spanish intensive care units]. / Política de visitas, diseño y confortabilidad en las unidades de cuidados intensivos españolas.

OBJECTIVE: To determine the design and comfort in the Intensive Care Units (ICUs), by analysing visiting hours, information, and family participation in patient care. DESIGN: Descriptive, multicentre study. SETTING: Spanish ICUs. METHODS: A questionnaire e-mailed to members of the Spanish Society of Intensive Care Medicine, Critical and Coronary Units (SEMICYUC), subscribers of the Electronic Journal Intensive Care Medicine, and disseminated through the blog Proyecto HU-CI. RESULTS: A total of 135 questionnaires from 131 hospitals were analysed. Visiting hours: 3.8% open 24h, 9.8% open daytime, and 67.7% have 2 visits a day. Information: given only by the doctor in 75.2% of the cases, doctor and nurse together in 4.5%, with a frequency of once a day in 79.7%. During weekends, information is given in 95.5% of the cases. Information given over the phone 74.4%. Family participation in patient care: hygiene 11%, feeding 80.5%, physiotherapy 17%. Personal objects allowed: mobile phone 41%, computer 55%, sound system 77%, and television 30%. Architecture and comfort: all individual cubicles 60.2%, natural light 54.9%, television 7.5%, ambient music 12%, clock in the cubicle 15.8%, environmental noise meter 3.8%, and a waiting room near the ICU 68.4%. CONCLUSIONS: Visiting policy is restrictive, with a closed ICU being the predominating culture. On average, technological communication devices are not allowed. Family participation in patient care is low. The ICU design does not guarantee privacy or provide a desirable level of comfort.

Quantitative evaluation of cellular uptake, DNA incorporation and adduct formation in cisplatin sensitive and resistant cell lines: Comparison of different Pt-containing drugs.

The use of Pt-containing compounds as chemotherapeutic agents facilitates drug monitoring by using highly sensitive elemental techniques like inductively coupled plasma mass spectrometry (ICP-MS). However, methodological problems arise when trying to compare different experiments due to the high variability of biological parameters. In this work we have attempted to identify and correct such variations in order to compare the biological behavior of cisplatin, oxaliplatin and pyrodach-2 (a novel platinum-containing agent). A detailed study to address differential cellular uptake has been conducted in three different cell lines: lung adenocarcinoma (A549); cisplatin-sensitive ovarian carcinoma (A2780); and cisplatin-resistant ovarian carcinoma (A2780cis). The normalization of Pt results to cell mass, after freeze-drying, has been used to minimize the errors associated with cell counting. Similarly, Pt accumulation in DNA has been evaluated by referencing the Pt results to the DNA concentration, as measured by (31)P monitoring using flow-injection and ICP-MS detection. These strategies have permitted to address significantly lower Pt levels in the resistant cells when treated with cisplatin or oxaliplatin as well as an independent behaviour from the cell type (sensitive or resistant) for pyrodach-2. Similarly, different levels of incorporation in DNA have been found for the three drugs depending on the cell model revealing a different behavior regarding cell cisplatin resistance. Further speciation experiments (by using complementary HPLC-ICP-MS and HPLC-ESI-Q-TOF MS) have shown that the main target in DNA is still the N7 of the guanine but with different kinetics of the ligand exchange mechanism for each of the compounds under evaluation.

Enhanced detection of DNA sequences using end-point PCR amplification and online gel electrophoresis (GE)-ICP-MS: determination of gene copy number variations.

The design and evaluation of analytical methods that permit quantitative analysis of specific DNA sequences is exponentially increasing. For this purpose, highly sensitive methodologies usually based on labeling protocols with fluorescent dyes or nanoparticles are often explored. Here, the possibility of label-free signal amplification using end-point polymerase chain reaction (PCR) are exploited using on-column agarose gel electrophoresis as separation and inductively coupled plasma-mass spectrometry (ICP-MS) for the detection of phosphorus in amplified DNA sequences. The calibration of the separation system with a DNA ladder permits direct estimation of the size of the amplified gene fragment after PCR. With this knowledge, and considering the compound-independent quantification capabilities exhibited by ICP-MS for phosphorus (it is only dependent on the number of P atoms per molecule), the correlation of the P-peak area of the amplified gene fragment, with respect to the gene copy numbers (in the starting DNA), is then established. Such a relationship would permit the determination of copy number variations (CNVs) in genomic DNA using ICP-MS measurements. The method detection limit, in terms of the required amount of starting DNA, is ∼6 ng (or 1000 cells if 100% extraction efficiency is expected). The suitability of the proposed label-free amplification strategy is applied to CNVs monitoring in cells exposed to a chemical agent capable of deletion induction, such as cisplatin.

Conocimiento sobre el ácido fólico en la prevención de defectos de cierre del tubo neural: una encuesta a mujeres que viven en Santiago de Chile / Awareness of post partum women on the effects of folie acid in the prevention of congenital anomalies

Background: Wheat flour in Chile is fortified with folie acid and pregnant women are also supplemented with the vitamin, but the population level of knowledge or awareness about this vitamin and its use by pregnant women is unknown. Aim: To assess the level of knowledge that postpartum women from Santiago de Chile have about folie acid. Material and methods: A questionnaire about folie acid and its efects on the prevention of neural tube defects was developed adapting questionnaires designed abroad. It was applied by medical students to puerperal women, hospitalized in public hospitals. Results: The questionnaire was applied to 342 women aged 26 ± 7 years. Sixty one percent were housewives and 55 percent completed high school education. Forty seven percent of these women had heard about folie acid, 9.6 percent knew that it was able to prevent congenital defects and only one received an adequate supplementation during pregnancy. Women aged 25 to 34 years and those with an adequate medical care during pregnancy had a significantly better knowledge about folie acid and its role in the prevention of congenital anormalies. The more commom means to receive information about folie acid were midwifes (34 percent), mass media (28 percent) and doctors (20 percent). Two hundred eleven women (62 percent) agreed to take folie acid in a future gestation and 58 percent preferred to do so using fortified foods. Conclusions: Post partum women from Santiago have a poor knowledge about the relevance of folie acid supplementation.

[Awareness and knowledge of the use of folic acid in the prevention of neural tube defects: a survey of women living in Santiago, Chile]. / Conocimiento sobre el ácido fólico en la prevención de defectos de cierre del tubo neural: una encuesta a mujeres que viven en Santiago de Chile.

BACKGROUND: Wheat flour in Chile is fortified with folie acid and pregnant women are also supplemented with the vitamin, but the population level of knowledge or awareness about this vitamin and its use by pregnant women is unknown. AIM: To assess the level of knowledge that postpartum women from Santiago de Chile have about folic acid. MATERIAL AND METHODS: A questionnaire about folic acid and its effects on the prevention of neural tube defects was developed adapting questionnaires designed abroad. It was applied by medical students to puerperal women, hospitalized in public hospitals. RESULTS: The questionnaire was applied to 342 women aged 26 +/- 7 years. Sixty one percent were housewives and 55% completed high school education. Forty seven percent of these women had heard about folic acid, 9.6% knew that it was able to prevent congenital defects and only one received an adequate supplementation during pregnancy. Women aged 25 to 34 years and those with an adequate medical care during pregnancy had a significantly better knowledge about folic acid and its role in the prevention of congenital anomalies. The more common means to receive information about folic acid were midwives (34%), mass media (28%) and doctors (20%). Two hundred eleven women (62%) agreed to take folic acid in a future gestation and 58% preferred to do so using fortified foods. CONCLUSIONS: Post partum women from Santiago have a poor knowledge about the relevance of folic acid supplementation.

Conocimiento y uso de ácido fólico periconcepcional: estudio comparativo entre puérperas adolescentes y adultas en Santiago de Chile / Knowledge and use of periconceptional folic acid

Introduction: intake of Folic Acid (FA) before conception and during early pregnancy reduces the incidence of neural tube defects (NTD). In Chile the management of the pregnant adolescent women is a relevant public health problem. So, the aim of this study was to determine the level of knowledge and intake of FA in a sample of adolescent and older parturient. Methods: a survey was conducted in one group of teenagers (group A) and another group of older puerperal (group B) corresponding to four public maternities of Santiago. Results: finally, 79 teenagers and 263 older women were surveyed. Both groups showed a poor knowledge about the benefit of intake of FA during this period. Regarding the control before pregnancy, we found an attendance of 10.1 percent in the group A and 24.7 percent in the group B, whereas only 5.1 percent of the group A and 1.9 percent of the group B had an intake of FA according to the medical recommendation. Conclusion: our patients have scanty information about the benefits of the periconceptional intake of FA. It seems necessary to design new methods and tools in order to increase the use of the FA in women of childbearing age, especially in the groups at risk for NTD.

Flurbiprofen loaded biodegradable nanoparticles for ophtalmic administration.

Poly(lactic/glycolic) acid nanoparticles incorporating flurbiprofen (FB) were prepared by the solvent displacement technique using poloxamer 188 as a stabilizer to improve the availability of the drug for the prevention of the inflammation caused by ocular surgery. A 2(3) + star design was applied to investigate the influence of several factors such as the pH of the aqueous phase, the initial concentration of the stabilizer, and the drug used to prepare the nanoparticles (NPs) on the physicochemical properties (particle size analysis, zeta potential, and drug loading efficiency) of the colloidal system. The best formulations were those prepared at pH 3.5 with a concentration of 1.5 mg/mL of FB and 10 or 20 mg/mL of poloxamer 188. These formulations showed an appropriate average size for ophthalmic administration (232.8 and 277.6 nm, respectively) and a good yield of entrapment efficiency (94.60% and 93.55%, respectively). The release behavior of FB from the developed NPs was complete and exhibited a biphasic pattern. Formulations did not show toxicity on ocular tissues. In vivo anti-inflammatory efficacy was assessed in the rabbit eye after topical instillation of sodium arachidonate (SA). A higher decrease of the SA-induced inflammation was obtained for the NP formulations.

Influence of the saturation chain and head group charge of phospholipids in the interaction of hepatitis G virus synthetic peptides.

Using the Langmuir technique, we have studied the properties at the air/water interface and the interaction of the hepatitis G virus synthetic peptide E1(53-66) and its palmitoyl derivative with membrane phospholipids. These phospholipids had different characteristics referring to the net charge and saturation of the acyl chain. The palmitoyl derivative was more stable at the air/water interface and in the kinetic at constant area measurements showed higher incorporation to the monolayer. The interaction was higher for saturated phospholipids and those with a negative net charge. When the peptides were in the subphase, they produced changes in the miscibility of mixed monolayers composed of DPPC/DPPG or DOPC/DOPG. It can be deduced from the results obtained that electrostatic interactions play a major role, but when the peptide is derivatized with the palmitoyl chain, hydrophobic interactions are added to the former ones. The interaction is also influenced by the saturation of the acyl chain.

Stability and ocular tolerance of cyclophosphamide-loaded nanospheres.

The physical and chemical stabilities of several formulations of cyclophosphamide-loaded polybutylcyanoacrylate (PBCA) nanospheres developed for an ophthalmic application as an immunosuppressive agent were studied over 6 months of storage at 4, 25 and 40 degrees C in different experimental conditions. The physical stability of nanospheres was followed by the study of morphological (visual appearance) and morphometrical properties (mean particle size and polydispersity). The pH and tonicity of the suspensions and the association efficiency of the drug to polymeric system were also analysed to evaluate their chemical stability. The behaviour of colloidal suspensions with storage conditions was also followed by differential scanning calorimetry. The degradation of PBCA was affected by temperature and pH. The average particle size of all nanospheres remained practically unchanged throughout the study, with the polydispersity index being less than 0.1, corresponding to a monodisperse system. At 40 degrees C, a loss of 25.9% of the initial association efficiency, especially in non-buffered pH 7.2 medium, was observed. The type of polymer degradation (surface erosion) was also determined by photon correlation spectroscopy. The results obtained from in vivo study of ocular tolerance indicate a good ocular tolerance for drug loaded to nanospheres.

Synthesis and physicochemical study of the laminin active sequence: SIKVAV.

The synthesis, physicochemical characterization, and interaction with membrane model systems of a peptide derived from the PA22-2 region of laminin are described. Surface activity studies indicate that this peptide is able to spread at the air-water interface being the maximal spreading pressure 20 mN/m at subphase concentrations around 10 micro M. Besides, these peptide molecules are also able to form stable monolayers. Physicochemical studies concerning the interaction of this peptide with lipids, organized in mono and bilayers, were carried out using Langmuir balance experiments and polarization fluorescence techniques. The peptide penetrates better in monolayers of DPPC than in those of PC and forms condensed mixed monolayers with DPPC. Energies of mixing are small thus indicating that deviations from ideality were almost negligible. Interactions with bilayers were studied through microviscosity changes (DPH and TMA-DPH probes), membrane permeability alterations (CF, NBD-PE/dithionite), and fusion promotion (NBD-PE/Rh-PE, resonance energy transfer). Results indicate that this sequence interacts very softly with bilayers without promoting changes in their organization. These data as well as the lack of interaction with erythrocytes suggest that coating liposomes with this peptide through chemical amide bonds can render stable inmunoliposomes for further biological applications.