Maria I. Montañez

Stability and biocompatibility of a library of polyester dendrimers in comparison to polyamidoamine dendrimers

Dendrimers can be designed for several biomedical applications due to their well-defined structure, functionality and dimensions. The present study focused on the in vitro biocompatibility evaluation of a library of aliphatic polyester dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) with an overall diameter of 0.5-2 nm. In addition, dendrimers with two different chemical surfaces (neutral with hydroxyl end group and anionic with carboxylic end group) and dendrons corresponding to the structural fragments of the dendrimers were evaluated. Commercial polyamidoamine dendrimers (PAMAM) with cationic (amine) or neutral (hydroxyl) end group were also included for comparison. Cell viability studies were conducted in human cervical cancer (HeLa) and acute monocytic leukemia cells (THP.1) differentiated into macrophage-like cells as well as in primary human monocyte-derived macrophages. Excellent biocompatibility was observed for the entire hydroxyl functional bis-MPA dendrimer library, whereas the cationic, but not the neutral PAMAM exerted dose-dependent cytotoxicity in cell lines and primary macrophages. Studies to evaluate material stability as a function of pH, temperature, and time, demonstrated that the stability of the 4th generation hydroxyl functional bis-MPA dendrimer increased at acidic pH. Taken together, bis-MPA dendrimers are degradable and non-cytotoxic to human cell lines and primary cells.

Cephalosporin chemical reactivity and its immunological implications.

Purpose of reviewThe aim of this article is to analyze the chemical reactivity of cephalosporins resulting in the epitope responsible for recognition by IgE antibodies and to establish the basis of the allergenicity. Recent findingsIncreasing evidence supports the role of cephalosporins in IgE hypersensitivity reactions. Third and fourth generation cephalosporins appear to be more involved in specific IgE reactions and often no cross-reactivity with traditional benzyl penicillin determinants exists. In some instances selective responses to unique cephalosporins occur and in others common side-chain similarities exist. SummaryLack of knowledge of the exact chemical structure of cephalosporin antigenic determinants has hindered clinical interpretation of allergic reactions to these drugs and hampered understanding of the specific recognition by IgE molecules of these determinants. Data indicate that R2 is not present in the final conjugate and that recognition by IgE antibodies is mainly directed to the R1 acyl side chain and to the β-lactam fragment that remains linked to the carrier protein in the cephalosporin conjugation process.

Role of minor determinants of amoxicillin in the diagnosis of immediate allergic reactions to amoxicillin

To cite this article: Torres MJ, Ariza A, Fernández J, Moreno E, Laguna JJ, Montañez MI, Ruiz‐Sanchez AJ, Blanca M. Role of minor determinants of amoxicillin in the diagnosis of immediate allergic reactions to amoxicillin. Allergy 2010; 65: 590–596.

Bifunctional Dendronized Cellulose Surfaces as Biosensors

Well-defined dendronized cellulose substrates displaying multiple representations of dual-functionality were constructed by taking advantage of the efficiency of the click reaction combined with traditional anhydride chemistry. First, activated cellulose surfaces were decorated with several generations of dendrons, and their peripheral reactive groups were subsequently reacted with a trifunctional orthogonal monomer. The generated substrate tool box was successfully explored by accurately tuning the surface function using a versatile orthogonal dual postfunctionalization approach. In general, the reactions were monitored by using a click-dye reagent or a quartz crystal microbalance (QCM) technique, and the resulting surfaces were well-characterized using XPS, FT-IR, and contact angle measurements. Utilizing this approach two different surfaces have been obtained; that is, triethylenglycol oligomers and amoxicillin molecules were efficiently introduced to the dendritic surface. As a second example, mannose-decorated hydroxyl functional surfaces illustrated their potential as biosensors by multivalent detection of lectin protein at concentration as low as 5 nM.

Immediate allergic reactions to betalactams: facts and controversies.

Purpose of reviewTo analyse the available data in the field of immediate allergic reactions to β-lactams, with particular emphasis on more recent studies, and to comment on the future role of this group of antibiotics. Recent findingsThe world of β-lactams has become more complex than initially thought, due to the increased number of chemical structures available, the wide variety of indications for their use in treating different infectious diseases, and possibly also due to the interaction of other as yet undetermined factors. Benzyl penicillin, the original inducer of allergic reactions, has now largely been replaced by amoxicillin and, to a lesser extent, by cephalosporins in inducing IgE-mediated allergic reactions. These structures often share extensive cross-reactivity, eliciting clinical reactions to many compounds, especially amongst penicillins. In other circumstances selective responses are observed which are restricted to one group or one single compound, as occurs in the group of cephalosporins. The application of new determinants for skin testing and the use of adapted in-vitro studies have enabled these findings to be confirmed in detail. SummaryResults indicate that evaluation of immediate reactions to β-lactams requires the use of several determinants for both in-vitro and in-vivo testing, and which must reflect the relevant drug involved in eliciting the response. This tendency will be strengthened in the future if use of benzyl penicillin continues to decrease as a drug to which populations are exposed.

Linear dendritic polymeric amphiphiles with intrinsic biocompatibility: synthesis and characterization to fabrication of micelles and honeycomb membranes

Linear dendritic hybrid materials enable a range of architectural variations which offers novel possibilities in the tailoring of polymeric materials. In this study dendrons based on the 2,2-bis(methylol)propionic acid (bis-MPA) building block, bearing click chemistry moieties in the core and peripheral hydroxyl functionalities, have been used as macroinitiators for ring opening polymerization of e-caprolactone. A library of star branched polymers with poly(e-caprolactone) chains was initially constructed using dendrons up to 4th generation. In a second step, the popular CuAAC or thiol–ene click reaction was efficiently used to attach poly(ethylene glycol) chains of different lengths to the core. Potential applications of the resulted amphiphilic linear dendritic hybrids were investigated. Both self-assembled micelles loaded with doxorubicin anticancer drug and ordered honeycomb membranes with enhanced surface area were successfully fabricated and characterized.

Skin testing for immediate hypersensitivity to betalactams: comparison between two commercial kits

Introduction:  Skin testing with major and minor determinants of benzylpenicillin is the recommended standard practice to evaluate subjects with immediate hypersensitivity to betalactams. The withdrawal of these products from the market has set us back to the early days, before the introduction of reagents for in vivo testing.

Highly Adhesive Phenolic Compounds as Interfacial Primers for Bone Fracture Fixations

Bone fractures are today stabilized with screws and metal plates. More complicated fractures require alternative treatments that exclude harsh surgical conditions. By adapting the benign and UV initiated thiol-ene reaction, we efficiently fabricated triazine-based, fiber-reinforced adhesive patches within 2 s. To enhance their bone adhesion properties, we found that a pre-treatment step of bone surfaces with phenolic dopamine and poly(parahydroxystyrene) compounds was successful. The latter display the greatest E-module of 3.4 MPa in shear strength. All patches exhibited low cytotoxicity and can therefore find potential use in future treatments of bone fractures.

Dendrimerized cellulose as a scaffold for artificial antigens with applications in drug allergy diagnosis.

Cellulose-based dendrimerized material was prepared and its quality was assessed by determining the number of amine functional groups incorporated. Based on the results for a series of preparations, the material was obtained in a highly reproducible manner thanks to the particular chemical construction method used. The number of amine groups incorporated and the amount of dendrimer attached are directly related to the dendrimer generation. The combination of the properties of the cellulose polymer and those of the dendrimeric state provides biocompatible materials amenable to easy chemical characterization. The proposed method provides an effective tool for developing clinically testable materials with a view to studying adverse immunological responses to drugs in humans.

Dendrimer-Modified Solid Supports: Nanostructured Materials with Potential Drug Allergy Diagnostic Applications

Complex functional materials consisting of bioactive molecules immobilized on solid supports present potential applications in biosensoring. Advances in the fabrication of these surface materials are of growing interest for antibody-based diagnosis. This work exploits dendrimers as versatile nanostructures for templating sensor surfaces and the critical role of the immobilization protocol in the solid supports cellulose and zeolites, of organic and inorganic composition respectively. The fabrication and characterization, including the degree of functionalization and reproducibility, of different nanostructured materials are described. To validate the approach, the fabricated supports were further used as a solid phase for developing a radioimmunoassay to detect immunoglobulin E (IgE) specific to penicillin, the antibody involved in immediate allergy responses to this drug. The dendrimer-modified supports provide assays with significantly enhanced sensitivity, as well as increase the availability of biomolecules for specific interaction and minimize nonspecific adsorptions through appropriate functionalization protocols in each case. The manufacturing methodology involved the use of a long, flexible hydrophilic spacer in the cellulose materials, and a higher surface density of the immobilized dendrimers in the zeolite crystals. The ability of hybrid zeolite materials in such biosensing applications was evaluated for the first time. The assays were validated in human serum samples from patients allergic to penicillin and from non-allergic controls. The specificity and improved sensitivity of the dendrimer- modified supports make these strategies versatile for different bioactive molecules and could have significant implications for the quantification of a wide range of specific IgE antibodies and other biomolecules of diagnostic interest.