Non-immediate drug hypersensitivity reactions secondary to intravitreal anti-vascular endothelial growth factors.

PURPOSE: To describe a series of non-immediate drug hypersensitivity reactions after intravitreal anti-vascular endothelial growth factors (anti-VEGFs). PATIENTS AND METHODS: Retrospective report of 6 patients with cutaneous non-immediate drug hypersensitivity reactions following intravitreal anti-VEGF injections, 4 after ranibizumab, 1 after bevacizumab and 1 after aflibercept. RESULTS: Clinical manifestations ranged from mild maculopapular rash, purpura to severe generalized erythroderma, with or without systemic involvement such as microscopic hematuria and proteinuria or fever. In two out of the six patients, reintroduction of either the same or an alternative anti-VEGF drug did induce a recurrence of the drug hypersensitivity reaction, while 4 patients showed no recurrence. CONCLUSION: Cutaneous non-immediate drug hypersensitivity reactions secondary to intravitreal anti-VEGF may occur. Continuation of the same drug or switch to another anti-VEGF may either induce recurrence or be well supported by the patient. The decision of drug discontinuation should be guided by the severity of the disease.

[Spanish Society of Anaesthesia (SEDAR) guidelines for pre-anaesthesia checking procedures]. / Directrices de procedimientos de comprobación y validación («chequeo¼) previos a la anestesia de la Sociedad Española de Anestesiología.

We present this document as a guide to preparing a specific institutional pre-anaesthesia checklist, as recommended in the Helsinki declaration on patient safety in anaesthesiology. Also, the recently recommended WHO "safe surgery check-list" includes a check-list for anaesthesia. A working group was established in accordance with the charter of the Spanish Society of Anaesthesiology and Resuscitation (Sociedad Española de Anestesiología y Reanimación [SEDAR]). The new patient safety culture introduced into medicine, and the recommendations of European anaesthesia societies has led us to design and update protocols in order to improve results in this important part of our speciality. We have prepared these recommendations or guidelines using, as examples, updates of pre-anaesthesia check-lists by other American (ASA), British, or Canadian societies of anaesthesia. With that aim, we enlisted the help of anaesthesia ventilator experts and the participation and advice of experienced anaesthesiologists from all parts of Spain. After various corrections and modifications, the document was available at www.sedar.es, so that any anaesthesiologist could propose any correction, or give their opinion. Finally, these guidelines have been approved by the SEDAR Board of Directors, before it was sent for publication in this journal. The aims of this document are to provide: a guideline applicable to all anaesthesia machines, a descriptive pre-anaesthesia check-list that include everything necessary for the anaesthesia procedure, and a resumed check-list to be available in all the anaesthesia machines or other equivalent, but prepared for each institution, which should include anaesthetic equipment and drugs. So, in order to ensure the aims and requirements of the European Board of Anaesthesiology, the European Society of Anaesthesiology, and the WHO are met, each institution should have a protocol for checking equipment and drugs. These guidelines are applicable to any anaesthesia equipment, enabling every institution to develop their own checking protocols, adapted to their anaesthesia machines and their procedures. With the consent of the SEDAR, this group will collaborate with anaesthesia machines providers in order to develop specific checklists for each of their models that will be available at www.sedar.es.

Directrices de procedimientos de comprobación y validación («chequeo») previos a la anestesia de la Sociedad Española de Anestesiología / Spanish Society of Anaesthesia (SEDAR) guidelines for pre-anaesthesia checking procedures

Este documento que presentamos pretende servir de guía para la elaboración por cada centro de una lista de chequeo previo a la anestesia o pre-anestesia, tal y como recomienda la reciente declaración de Helsinki sobre seguridad del paciente en anestesia. Además, la reciente implantación del «check-list quirúrgico de la OMS» (safe surgery check-list) incluye un epígrafe de chequeo de anestesia. El grupo de trabajo se constituyó con este fin según los estatutos de la Sociedad Española de Anestesiología, Reanimación y Tratamiento del Dolor (SEDAR). La nueva cultura de seguridad del paciente que se está implantando en la práctica médica y las recomendaciones de las sociedades europeas de anestesia nos obligan a actualizar y realizar protocolos que mejoren los resultados en este aspecto fundamental de nuestra especialidad. Tomando como ejemplo las actualizaciones de las listas de comprobación de diferentes asociaciones de anestesiólogos como la americana, británica o canadiense, hemos elaborado esta propuesta. Para ello hemos contado con la ayuda de expertos en respiradores y la colaboración y consejos de anestesiólogos expertos de todas las comunidades autónomas. Después de sucesivas correcciones, fue publicada en la página web de la SEDAR para que cualquier anestesiólogo pudiera aportar sus correcciones o su opinión. Finamente el documento ha sido aprobado por la junta directiva de la SEDAR, antes de ser enviado para su publicación en esta revista. Los objetivos de este documento son: proporcionar unas directrices o recomendaciones de comprobación aplicables a todos los sistemas de anestesia, realizar un listado descriptivo de comprobación que incluya todos los elementos necesarios para el procedimiento anestésico y aportar un listado con los elementos del chequeo en forma de esquema para disponer de él en cada equipo de anestesia o de otro similar realizado por cada centro, que incluya respirador, monitores, material auxiliar y fármacos. Por tanto, para cumplir con las recomendaciones de seguridad del paciente del European Board of Anaesthesiology (EBA), European Society of Anaesthesiology (ESA) y de la OMS, cada centro debe elaborar una lista de comprobación y verificación (en adelante «chequeo») previo a la anestesia. Este documento proporciona unas directrices aplicables a todos los sistemas de anestesia de tal manera que cada departamento pueda desarrollar sus propios protocolos de comprobación, adaptados a sus equipos de anestesia y a sus procedimientos de trabajo. De acuerdo con la directiva de la SEDAR, este grupo de trabajo colaborará con los fabricantes de equipos de anestesia para desarrollar listas de comprobación específicas de cada uno de sus modelos para que estén disponibles en www.sedar.es(AU)

We present this document as a guide to preparing a specific institutional pre-anaesthesia checklist, as recommended in the Helsinki declaration on patient safety in anaesthesiology. Also, the recently recommended WHO "safe surgery check-list" includes a check-list for anaesthesia. A working group was established in accordance with the charter of the Spanish Society of Anaesthesiology and Resuscitation (Sociedad Española de Anestesiología y Reanimación [SEDAR]). The new patient safety culture introduced into medicine, and the recommendations of European anaesthesia societies has led us to design and update protocols in order to improve results in this important part of our speciality. We have prepared these recommendations or guidelines using, as examples, updates of pre-anaesthesia check-lists by other American (ASA), British, or Canadian societies of anaesthesia. With that aim, we enlisted the help of anaesthesia ventilator experts and the participation and advice of experienced anaesthesiologists from all parts of Spain. After various corrections and modifications, the document was available at www.sedar.es, so that any anaesthesiologist could propose any correction, or give their opinion. Finally, these guidelines have been approved by the SEDAR Board of Directors, before it was sent for publication in this journal. The aims of this document are to provide: a guideline applicable to all anaesthesia machines, a descriptive pre-anaesthesia check-list that include everything necessary for the anaesthesia procedure, and a resumed check-list to be available in all the anaesthesia machines or other equivalent, but prepared for each institution, which should include anaesthetic equipment and drugs. So, in order to ensure the aims and requirements of the European Board of Anaesthesiology, the European Society of Anaesthesiology, and the WHO are met, each institution should have a protocol for checking equipment and drugs. These guidelines are applicable to any anaesthesia equipment, enabling every institution to develop their own checking protocols, adapted to their anaesthesia machines and their procedures. With the consent of the SEDAR, this group will collaborate with anaesthesia machines providers in order to develop specific checklists for each of their models that will be available at www.sedar.es(AU)

Abordaje multidisciplinar en el tratamiento de una hemoptisis grave con amenaza vital / Multidisciplinary approach to treating lifethreatening massive hemoptysis

La hemoptisis masiva es una situación clínica alarmante en la que la asfixia por aspiración de sangre constituye la principal amenaza para la vida. Su etiología requiere un amplio diagnóstico diferencial y queda sin determinar en un 5-20% de los casos. La hipoxemia y el resangrado son complicaciones que pueden ser mortales. Presentamos el caso de un paciente de 68 años de edad sin antecedentes patológicos de interés, que pudo ser tratado con éxito de las complicaciones de una hemoptisis masiva gracias a un consenso multidisciplinar(AU)

Massive hemoptysis is an alarming event in which asphyxiation due to aspiration of blood is the main threat. The differential diagnosis taking into consideration a wide range of potential causes is required, and in 5% to 20% of cases, the reason for bleeding is never established. Hypoxemia and rebleeding are the main life-threatening complications. We describe the case of a 68-year-old man with no relevant medical history whose massive hemoptysis and complications were treated successfully by a multidisciplinary team(AU)

[Multidisciplinary approach to treating life-threatening massive hemoptysis]. / Abordaje multidisciplinar en el tratamiento de una hemoptisis grave con amenaza vital.

Massive hemoptysis is an alarming event in which asphyxiation due to aspiration of blood is the main threat. The differential diagnosis taking into consideration a wide range of potential causes is required, and in 5% to 20% of cases, the reason for bleeding is never established. Hypoxemia and rebleeding are the main life-threatening complications. We describe the case of a 68-year-old man with no relevant medical history whose massive hemoptysis and complications were treated successfully by a multidisciplinary team.

Desviación traqueal secundaria a un bocio / No disponible

No disponible

[Problem-based learning in an undergraduate medical school course on anesthesiology, recovery care, and pain management]. / El aprendizaje basado en problemas aplicado a la asignatura de pregrado de anestesiología, reanimación y terapéutica del dolor.

INTRODUCTION: We describe our experience with problem-based learning (PBL) in an undergraduate course in anesthesiology and recovery care. MATERIAL AND METHODS: The study was carried out over 5 consecutive academic years from 2000 through 2005. In total, 168 students took part. PBL was started in seminars in the first 3 years the course was given. In the last 2 years, PBL was used throughout the entire course, which consisted of 12 seminars. At the end, each student evaluated the activities overall, the tutor's intervention, the student's own participation, and the time invested in searching for information and preparing for discussions. RESULTS: In the first 3 years, most students considered they had better assimilated the knowledge presented and that they had participated more. In the last 2 years, assessment of the course overall reached a score of 8.47 (SD, 1.24); of the instructor, 8.84 (0.98); and of student participation, 7.38 (1.29). The students used 2.11 (1.43) hours to search for information and 1.74 (1.14) hours to prepare for discussion. CONCLUSIONS: The medical students' level of satisfaction with and acceptance of PBL in this anesthesiology course were high. The instructor's intervention and student participation were assessed highly. A large amount of time was used for study.

El aprendizaje basado en problemas aplicado a la asignatura de pregrado de Anestesiología, Reanimación y Terapéutica del Dolor / Problem-based learning in an undergraduate medical school course on anesthesiology, recovery care, and pain management

INTRODUCCIÓN: El objetivo de este trabajo es presentarnuestra experiencia con el método de “Aprendizajebasado en problemas” (ABP) en la enseñanza universitariade Anestesiología y Reanimación.MATERIAL Y MÉTODOS: El estudio se realizó durante 5cursos consecutivos desde el 2000 hasta el 2005, y en élparticiparon 168 estudiantes. En los 3 primeros años seinició el ABP con tres seminarios. En los dos últimos elsistema se utilizó para toda la asignatura y consistió en12 seminarios al final de los cuales el alumno tenía queevaluar globalmente la actividad, la intervención deltutor, su propia participación y el tiempo empleado en labúsqueda de la información y en la preparación de ladiscusión.RESULTADOS: En los tres primeros años, la mayor partede los estudiantes consideraron tener una mayor asimilaciónde conocimientos y una mayor participación enclase. En los dos últimos, la valoración global de la asignaturafue de 8,47 ± 1,24 (x ± DS), el papel del tutor 8,84± 0,98 y la participación del alumno de 7,38 ± 1,29. Elnúmero de horas/alumno empleadas en la búsqueda dela información fue de 2,11 ± 1,43 y en la preparación deltema de 1,74 ± 1,14.CONCLUSIONES: El grado de satisfacción y la aceptacióndel ABP por parte de los alumnos de pregrado deAnestesiología son altos. La intervención del tutor y laparticipación del alumno fueron elevadas. El tiempoempleado en el proceso es largo

INTRODUCTION:We describe our experience with problem-based learning (PBL) in an undergraduate course inanesthesiology and recovery care.MATERIAL AND METHODS: The study was carried outover 5 consecutive academic years from 2000 through2005. In total, 168 students took part. PBL was startedin seminars in the first 3 years the course was given. Inthe last 2 years, PBL was used throughout the entirecourse, which consisted of 12 seminars. At the end, eachstudent evaluated the activities overall, the tutor's intervention,the student's own participation, and the timeinvested in searching for information and preparing fordiscussions.RESULTS: In the first 3 years, most students consideredthey had better assimilated the knowledge presentedand that they had participated more. In the last 2years, assessment of the course overall reached a score of8.47 (SD, 1.24); of the instructor, 8.84 (0.98); and of studentparticipation, 7.38 (1.29). The students used 2.11(1.43) hours to search for information and 1.74 (1.14)hours to prepare for discussion.CONCLUSIONS: The medical students' level of satisfactionwith and acceptance of PBL in this anesthesiologycourse were high. The instructor's intervention and studentparticipation were assessed highly. A large amountof time was used for study

[Anesthesia in 2 cases of resection of a renal tumor involving the vena cava]. / Anestesia en dos casos de resección de un tumor renal con extensión a la vena cava.

Renal tumors can be associated with a thrombus that affects the renal vein and even the inferior vena cava. Radical surgery may require a 2-phase approach involving different anesthetic techniques: an abdominal approach for removal of the kidney and a thoracic approach for extraction of the thrombus, with extracorporeal circulation and in some cases cessation of blood circulation. We present 2 cases in which nephrectomy and thrombectomy were carried out with the support of extracorporeal circulation. The thrombus was in the renal vein and the inferior vena cava, extending to the outlet to the right atrium in both cases. In 1 case a portion reached the bifurcation of the pulmonary artery. The operation was performed under hypothermia to reduce circulation and did not require aortic clamping, cardioplegia, or cessation of blood flow.

Anestesia en dos casos de resección de un tumor renal con extensión a la vena cava / Anesthesia in 2 cases of resection of a renal tumor involving the vena cava

Los tumores renales pueden asociarse a un tromboque afecte a la vena renal e incluso a la vena cava inferior.La cirugía radical puede requerir de una intervenciónen dos tiempos con necesidades anestésicas diferentes:un abordaje abdominal para la resección del riñón yotro torácico para la extracción del trombo con circulaciónextracorpórea y en algunos casos de parada circulatoria.Presentamos dos casos en que se realizó nefrectomía ytrombectomía con soporte de circulación extracorpórea.El trombo se encontraba en la vena renal y vena cavainferior hasta la entrada de la aurícula derecha enambos casos y en uno de ellos un fragmento se desprendióhasta la bifurcación de la arteria pulmonar. La intervenciónse realizó con hipotermia para disminuir los flujoscirculatorios y no requirió de pinzamiento aórtico,cardioplejia, ni parada circulatoria

Renal tumors can be associated with a thrombus thataffects the renal vein and even the inferior vena cava.Radical surgery may require a 2-phase approach involvingdifferent anesthetic techniques: an abdominal approachfor removal of the kidney and a thoracic approachfor extraction of the thrombus, with extracorporeal circulationand in some cases cessation of blood circulation.We present 2 cases in which nephrectomy and thrombectomywere carried out with the support of extracorporealcirculation. The thrombus was in the renal veinand the inferior vena cava, extending to the outlet to theright atrium in both cases. In 1 case a portion reachedthe bifurcation of the pulmonary artery. The operationwas performed under hypothermia to reduce circulationand did not require aortic clamping, cardioplegia, orcessation of blood flow

[Transvaginal contrast sonography of the uterus in the diagnosis of abnormal uterine blood loss: less hysteroscopies needed]. / Transvaginale contrastechoscopie van de uterus in de diagnostiek van abnormaal uterien bloedverlies: minder hysteroscopieën nodig.

OBJECTIVE: To determine the value of transvaginal saline-infusion sonography of the uterus in patients with abnormal uterine blood loss in terms of avoiding hysteroscopy. DESIGN: Prospective. METHOD: According to the protocol, transvaginal saline-infusion sonography was carried out on all consecutive patients with abnormal uterine blood loss (post-menopausal patients with an endometrial thickness of > or = 5 mm and all pre-menopausal patients with menorrhagia or metrorrhagia) in the St. Joseph hospital in Veldhoven, the Netherlands, during the period 1999-2001. If sonography did not provide an image suitable for assessment, or if intracavitary (pedunculated) lesions such as polyps or myomas were suspected, a planned therapeutic hysteroscopy was carried out. Patients indicated their perception of pain on a visual analogue scale. RESULTS: Saline-infusion sonography of the uterus was performed in 457 patients (age: 40-69 years). In 32 patients (7%) it did not result in a representative image. In 138 (32%) of the remaining 425 patients, a pedunculated lesion was suspected. In 262 (59%) of the 457 patients, diagnostic efforts were restricted to ultrasonic examination. This was combined with endometrial aspiration in 161 (61%) of these patients. In total, hysteroscopy was carried out in 195 of the 457 patients (43%). There were no complications. Pain was scored as 'none-little' by 292 patients (64%), 'moderate' by 76 (17%) and 'a great deal' by 48 (10%) patients. CONCLUSION: Saline-infusion sonography of the uterus is a safe diagnostic method in patients with abnormal uterine blood loss, which, in more than half the cases, can replace less well-tolerated diagnostic procedures.

Tumor cell killing by in vitro affinity-matured recombinant human monoclonal antibodies.

We have developed a method that allows the rapid improvement of the affinity of phage-displayed antibody fragments by selection on intact eukaryotic cells. A single chain Fv fragment, specific for the tumor-associated Ep-Cam molecule, was mutagenized by shuffling of the immunoglobulin light chain variable region and DNA shuffling of both heavy and light chain variable regions. Higher-affinity mutants were selected from small phage display libraries by cell panning under stringent conditions. When converted to an intact fully human antibody, the mutagenized anti-tumor monoclonal antibody displayed an affinity of 0.4 nM, a 15-fold improvement over the affinity of the original antibody. Compared to previously reported affinity maturation schemes, panning on intact cells does not require purified targets for selection and may be particularly useful when the target molecule can not be expressed as a recombinant molecule or easily purified without disrupting its native configuration. In vitro tumor cell killing assays demonstrated an improved performance of the higher-affinity antibody in complement-mediated tumor cell killing. In contrast, the lower-affinity antibody performed somewhat better in antibody-dependent cellular cytotoxicity assays and penetrated better in multicell spheroids of tumor cells, an in vitro model for the tumor penetration capacity of antibodies.

Structure-based design and evaluation of MHC class II binding peptides.

Structural information regarding binding of peptides to the major histocompatibility complex (MHC) class II molecule is of great use for the design of compounds that intervene in the interaction between the MHC-peptide-T-cell receptor (TCR) complex. These compounds can be applied in the treatment of T-cell-mediated auto-immune disease for specific modulation of the disease process. In case no crystal structure of the MHC molecule is available, homology models of the MHC molecule can be of importance. Here we describe the construction of a homology model of the MHC class II molecule and binding of the peptide, that are involved in experimental auto-immune encephalomyelitis, a rat model for human multiple sclerosis. The validity of the model was investigated using experimental data of peptides binding to this MHC molecule.

Exploring computational lead optimisation with affinity constants obtained by surface plasmon resonance for the interaction of PorA epitope peptides with antibody against Neisseria meningitidis.

LUDI is a program used for de novo structure-based design of ligands and can predict binding of ligands quantitatively using a scoring function. Here we evaluate LUDI in a lead optimisation study with ligands for the antibody MN12H2, that has been raised against outer membrane protein PorA epitope P1.16 of Neisseria meningitidis. The ligands were synthetic peptides that are derived from the smallest binding epitope (182)DTNNN(186). LUDI's fragment building rules are used for the proposal of new peptide-ligands for MN12H2 and were focused on replacements of Asp(186) in the epitope. Accordingly, a series of peptides was synthesised with isosteric mutations. The interaction of the peptides with MN12H2 was analysed with a surface plasmon resonance competition assay yielding equilibrium binding constants in solution (K(S)). The binding affinity seems to be largely determined by entropy, and the side chain of Asn(186) is sensitive for charge, inversion, hydrophobicity and size. Head-to-tail cyclisation of the peptide in a nine-amino-acid ring gives little reduction in affinity. It is concluded that the scoring function of LUDI does not help in optimisation of the peptide lead for MN12H2 binding. Other more elaborate molecular mechanics calculations show similar results. This implies that our current knowledge of molecular recognition is insufficient for explaining a case of peptide-protein binding, where the design process requires subtle changes in structure (from lead finding to lead optimisation).

Comparison of transvaginal ultrasonography and saline infusion sonography for the detection of intracavitary abnormalities in premenopausal women.

OBJECTIVE: To compare the diagnostic accuracy of transvaginal sonography (TVS) and saline infusion sonography (SIS) for detecting intracavitary abnormalities in premenopausal women with abnormal uterine bleeding. METHOD: Consecutive premenopausal women who underwent hysterectomy for abnormal uterine bleeding were included. All women underwent TVS and SIS before their hysterectomy. The findings at TVS and SIS were compared with the findings of the hysterectomy specimen. Sensitivity, specificity, and likelihood ratios were calculated. RESULTS: The results of 50 patients with abnormal uterine bleeding were evaluated. Histological examination revealed normal endometrial histology in 27 patients, submucous myomas in 13 patients and intracavitary polyps in 10 patients. The sensitivity of TVS in directly visualizing intracavitary abnormalities was 61% for a specificity of 96%. The likelihood ratio of presence of an intracavitary abnormality was 16 and the likelihood ratio of absence of such a finding was 0.41. When defining abnormality at TVS as direct visualization of an intracavitary abnormality or an increased endometrial thickness (cut-off level 5 mm), the sensitivity of TVS was 87% for a specificity of 56%, with corresponding likelihood ratios of 2 and 0.23, respectively. The sensitivity and specificity of SIS was 100% and 85% with likelihood ratios of 6 and 0.0, respectively. No intracavitary abnormality was missed by SIS. CONCLUSION: The diagnostic accuracy of SIS is higher than the accuracy of TVS. A combined approach using endometrial thickness measurement by TVS and, reserving SIS for patients with increased (> 5 mm) endometrial thickness, or endometrium inadequately visualized on TVS, is the optimal method of reducing the hysteroscopy rate.

Comparison of transvaginal sonography, saline infusion sonography, and hysteroscopy in premenopausal women with abnormal uterine bleeding.

PURPOSE: Saline infusion sonography (SIS) is a relatively new technique in the evaluation of abnormal uterine bleeding. We compared the diagnostic accuracy of SIS with that of transvaginal sonography (TVS) in the detection of intracavitary abnormalities in premenopausal women with abnormal uterine bleeding. METHODS: In this prospective study, consecutive premenopausal women who underwent a hysteroscopy for abnormal uterine bleeding also underwent TVS and SIS. The findings at TVS and SIS were compared with the hysteroscopic and histologic findings. Sensitivity, specificity, and likelihood ratios were calculated. Receiver operating characteristic curves were constructed to assess the performance of endometrial thickness measured using TVS. RESULTS: Sixty-two patients were included in the study. TVS demonstrated 60% sensitivity in directly visualizing intracavitary abnormalities and 93% specificity. The likelihood ratio of the presence of an intracavitary abnormality was 8, and the likelihood ratio of the absence of an intracavitary abnormality was 0.43. Defining an abnormality at TVS as direct visualization of an intracavitary abnormality or an endometrial thickness greater than 5 mm, TVS had an 85% sensitivity and a 21% specificity, with corresponding likelihood ratios of 1.1 and 0.71, respectively. For SIS, the sensitivity, specificity, and likelihood ratios of the presence and absence of intracavitary abnormalities were 88%, 95%, 10, and 0.13, respectively. CONCLUSIONS: SIS is more accurate in the diagnosis of intracavitary abnormalities in premenopausal women than is TVS. An approach using endometrial thickness measurement by TVS and reserving SIS for patients who have an endometrial thickness greater than 5 mm or an intracavitary abnormality visualized by TVS would be the most effective method to reduce the number of hysteroscopies.

Structure-activity relationships of water-soluble cationic methacrylate/methacrylamide polymers for nonviral gene delivery.

A number of water-soluble cationic carriers was evaluated as transfectant. Almost all studied cationic methacrylate/methacrylamide polymers were able to condense the structure of plasmid DNA, yielding polymer/plasmid complexes (polyplexes) with a size of 0.1-0.3 micron and a slightly positive zeta-potential, which can be taken up by cells, e.g., via endocytosis. However, the transfection efficiency and the cytotoxicity of the polymers differed widely: the highest transfection efficiency and cytotoxicity were observed for poly[2-(dimethylamino)ethyl methacrylate], p(DMAEMA). Assuming that polyplexes enter cells via endocytosis, p(DMAEMA) apparently has advantageous properties to escape the endosome. A possible explanation is that, due to its average pK(a) value of 7.5, p(DMAEMA) is partially protonated at physiological pH and might behave as a proton sponge. This might cause a disruption of the endosome, which results in the release of both the polyplexes and cytotoxic endosomal/lysosomal enzymes into the cytosol. On the other hand, the analogues of p(DMAEMA) studied here have a higher average pKa value and have, consequently, a higher degree of protonation and a lower buffering capacity. This might be associated with a lower tendency to destabilize the endosome, resulting in both a lower transfection efficiency and a lower cytotoxicity. Furthermore, molecular modeling showed that, of all studied polymers, p(DMAEMA) has the lowest number of interactions with DNA. We therefore hypothesized that the superior transfection efficiency of p(DMAEMA) containing polyplexes can be ascribed to an intrinsic property of p(DMAEMA) to destabilize endosomes combined with an easy dissociation of the polyplex once present in the cytosol and/or the nucleus.

Mapping the binding site of the small intestinal peptide carrier (PepT1) using comparative molecular field analysis.

The present study was undertaken to examine the relationship between chemical structure (steric and electrostatic fields) and affinity for the small intestinal oligopeptide carrier (PepT1) using comparative molecular field analysis (CoMFA), a three-dimensional approach towards building quantitative structure-activity relationships. Various biological activity parameters (Kt, Jmax, Pc) and molecular descriptors (CoMFA fields, isobutylalcohol/water distribution coefficients) were examined. The resulting field map provides information on the geometry of the binding site cavity and the relative weights of various properties in different site pockets for each of the substrates considered. The results indicate that carrier permeability (Pc), calculated as the ratio of the half-maximal concentration (Kt) and the maximal carrier flux (Jmax), is sensitive to composition, size and hydrophobicity of the ligands. The best model obtained showed a high correlation between the carrier permeability (Pc) and the steric (76.3% contribution) and electrostatic (23.7% contribution) molecular fields with a cross-validated r2 (q2) of 0.754. The model fitted the experimental data with a correlation coefficient of 0.993 and a standard error of 0.041, while the regression line between experimental and calculated Pc had a slope of 0.994 with an intercept of 0.009. These results lead to a better understanding of the molecular requirements for optimal drug-carrier interactions with the intestinal peptide transporter and offers a useful visual aid for designing new potentially interesting structures with affinity for the oligopeptide transporter PepT1.