Counting the Clicks in Fluorescent Polymer Networks.

We introduce a fluorescence-based methodology enabling the quantification of ligation points in photochemically prepared polymer networks. Well-defined α,ω-tetrazole-capped polymer strands prepared via RAFT polymerization are crosslinked under UV irradiation by a trimaleimide via nitrile imine mediated tetrazole-ene cycloaddition. Thus, for each linkage point a fluorescent pyrazoline ring is formed, resulting in fluorescent networks, which are degradable by aminolysis of the trithiocarbonate functionalities, leading to soluble fragments. The fluorescence emission of the soluble network fragments correlates directly with the number of pyrazoline moieties originally present in the network, thus providing a direct measure of the number of ligation points constituting the network. The herein introduced strategy based on a fluorescence readout is a powerful yet simple approach to quantify network formation processes applicable to a wide class of polymers accessible via RAFT.

6-(Aryldiazenyl)pyrazolo[1,5-a]pyrimidines as Strategic Intermediates for the Synthesis of Pyrazolo[5,1-b]purines.

A microwave-assisted approach for the regioselective synthesis of functionalized 6-(aryldiazenyl)pyrazolo[1,5-a]pyrimidin-7-amines from the cyclization of 3-oxo-2-(2-arylhydrazinylidene)butanenitriles with 5-amino-1H-pyrazoles under solvent-free conditions has been developed. This methodology was distinguished by its broad substrate scope, operational simplicity, high atom economy, and high-yielding without requiring chromatographic purification. In addition, an efficient and versatile palladium-catalyzed reductive azo cleavage is disclosed for the synthesis of diverse heteroaromatic 1,2-diamines, a valuable synthetic building block to develop new fused heteroaromatic systems. As synthetic example, several substituted pyrazolo[5,1-b]purines were synthesized in yields up to 96% by using microwave irradiation in the cyclocondensation of these 1,2-diamines with orthoesters.

7-Amino-5-methyl-2-phenyl-6-(phenyldiazenyl)pyrazolo[1,5-a]pyrimidine crystallizes with Z' = 2: pseudosymmetry and the formation of complex sheets built from N-H...N and C-H...pi(arene) hydrogen bonds.

The title compound, C(19)H(16)N(6), crystallizes with Z' = 2 in the space group P2(1)/n. The two molecules in the selected asymmetric unit are approximate mirror images of one another; most corresponding pairs of atoms are related by an approximate half-cell translation along [100]. Each molecule contains an intramolecular N-H...N hydrogen bond and the molecules are linked into complex sheets by a combination of two intermolecular N-H...N and four C-H...pi(arene) hydrogen bonds. Comparisons are made with some other 7-aminopyrazolo[1,5-a]pyrimidines.

Clinical and Endoscopic Characterization of Gastrointestinal Kaposi's Sarcoma in an Institution in Southwestern Colombia between 2011 and 2020

Kaposi's sarcoma is an angioproliferative neoplasm associated with the human herpesvirus 8. According to the clinical characteristics and the degree of immunosuppression, there are four epidemiological forms: classic, endemic, iatrogenic, and epidemic. The latter is associated with acquired immunodeficiency syndrome (AIDS) and 40% GI involvement. There is little epidemiological, clinical, and endoscopic evidence of the disease. This study sought to characterize this condition in a Colombian population and compare the findings with publications from other countries. One hundred thirty-five records of patients who consulted between 2011 and 2020 for Kaposi's sarcoma were reviewed, of which 24 had GI involvement. Epidemiological, clinical, endoscopic, and treatment characteristics were obtained. Twenty-two patients were men. There were 21 patients infected with human immunodeficiency virus (HIV; 87.5%) and 19 receiving antiretroviral therapy (90%); 33.3% had HIV viral load > 100,000 copies/mL. The CD4+ count was <50 cells/µL in 28.6% of cases, between 50 and 100 cells/µL in 19.0%, and between 100 and 200 cells/µL in 14.4%. The rate of infection by other opportunistic infections was 41.7%. There were GI symptoms in 33% of the patients, and the most frequent were hematochezia, abdominal pain, nausea, and diarrhea. Most had concomitant skin lesions (70.8%). GI lesions were located mainly in the oropharynx (41.7%), stomach (20.8%), and colon (16.7%). The most common endoscopic finding was maculopapular erythema. This article provided insight into the local epidemiology of gastrointestinal Kaposi's sarcoma. In contrast to studies in other populations, GI symptoms were more frequent in this one, and there was a difference in endoscopic findings. Studies with larger populations are needed.

El sarcoma de Kaposi es una neoplasia angioproliferativa asociada al virus del herpes humano 8. Según las características clínicas y el grado de inmunosupresión, son cuatro las formas epidemiológicas: clásica, endémica, iatrogénica y epidémica, esta última asociada al síndrome de inmunodeficiencia adquirida (SIDA) y con un 40% de compromiso gastrointestinal. Existe escasa evidencia epidemiológica, clínica y endoscópica de la enfermedad. Este estudio buscó caracterizar esta condición en una población colombiana y contrastar los hallazgos con publicaciones de otros países. Se revisaron 135 registros de pacientes que consultaron entre el 2011 y 2020 por sarcoma de Kaposi, de los cuales 24 tenían compromiso gastrointestinal. Se obtuvieron características epidemiológicas, clínicas, endoscópicas y tratamientos. Veintidós pacientes eran hombres. Hubo 21 pacientes infectados por virus de la inmunodeficiencia humana (VIH; 87,5%) y 19 recibían terapia antirretroviral (90%). El 33,3% tenía carga viral VIH > 100 000 copias/mL. El recuento de CD4+ fue < 50 cel/µL en el 28,6% de los casos, entre 50 y 100 cel/µL en el 19,0%, y entre 100 y 200 cel/µL en el 14,4%. La tasa de infecciones por otros oportunistas fue de 41,7%. Hubo síntomas gastrointestinales en el 33% de los pacientes y los más frecuentes fueron hematoquecia, dolor abdominal, náuseas y diarrea. La mayoría tuvo lesiones cutáneas concomitantes (70,8%). Las lesiones gastrointestinales se localizaron principalmente en la orofaringe (41,7%), estómago (20,8%) y colon (16,7%). El hallazgo endoscópico más común fue eritema maculopapular. Este artículo mostró una visión de la epidemiología local del sarcoma de Kaposi gastrointestinal. En contraste con estudios en otras poblaciones, en este, los síntomas gastrointestinales fueron más frecuentes y hubo diferencia en los hallazgos endoscópicos. Son necesarios estudios con poblaciones más grandes.

Pre-adsorption of antibodies enables targeting of nanocarriers despite a biomolecular corona.

To promote drug delivery to exact sites and cell types, the surface of nanocarriers is functionalized with targeting antibodies or ligands, typically coupled by covalent chemistry. Once the nanocarrier is exposed to biological fluid such as plasma, however, its surface is inevitably covered with various biomolecules forming the protein corona, which masks the targeting ability of the nanoparticle. Here, we show that we can use a pre-adsorption process to attach targeting antibodies to the surface of the nanocarrier. Pre-adsorbed antibodies remain functional and are not completely exchanged or covered by the biomolecular corona, whereas coupled antibodies are more affected by this shielding. We conclude that pre-adsorption is potentially a versatile, efficient and rapid method of attaching targeting moieties to the surface of nanocarriers.

Self-Reporting Fluorescent Step-Growth RAFT Polymers Based on Nitrile Imine-Mediated Tetrazole-ene Cycloaddition Chemistry.

We introduce an inherently fluorescent self-reporting step-growth polymer system as well as a fluorescence-based methodology for accessing the kinetics of the underpinning photoinduced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) process, using an equimolar mixture of a bismaleimide linker and a bifunctional α,ω-tetrazole-chain transfer agent (CTA). Similarly, α,ω-tetrazole-capped polystyrene, prepared via RAFT polymerization, was employed as a photoreactive macromonomer. Upon UV irradiation, the tetrazole moiety readily reacts with activated dialkenes producing the fluorescent pyrazoline-containing polymer. Thus, the fluorescence emission of the step-growth polymers is directly correlated with the number of ligation points in the polymer, forming an ideal self-reporting sensor system. The viability of the fluorescence-based quantification is verified via NMR spectroscopy, evidencing that fluorescence-based polymerization monitoring is a viable avenue in cases where NMR spectroscopy is difficult to conduct.

The pro-active payload strategy significantly increases selective release from mesoporous nanocapsules.

The controlled release of payloads from mesoporous silica nanocapsules (SiNCs) consisting of stimulus-responsive shells is of considerable interest in applications such as self-healing materials and drug delivery. However, the release of payloads from SiNCs before application of external triggers (i.e. non-selective release) remains a formidable challenge. In fact, the non-selective release of payloads from SiNCs occurs because of the mesoporous nature of the silica shell that cannot trap payloads in the core of SiNCs perfectly. We establish an efficient and straightforward strategy based on the encapsulation of a pro-active payload to hinder the non-selective release of small payloads from mesoporous capsules. A pro-active payload is defined as a compound that is converted to an active functional molecule in the environment where it is needed. In this sense, it is a generalization of a prodrug. Encapsulating a pro-active payload instead of a payload allowed hindering the non-selective release of the payload from SiNCs. A selective release of the payload could be achieved upon reduction of the encapsulated pro-active payload. Furthermore, the total amount of released substance is significantly enhanced by introducing responsive groups in the silica shell. These results show that the pro-active payload strategy combined with the use of stimulus-responsive materials can be successfully exploited to achieve selective release of cargo from mesoporous nanocapsules.

Multifunctional clickable and protein-repellent magnetic silica nanoparticles.

Silica nanoparticles are versatile materials whose physicochemical surface properties can be precisely adjusted. Because it is possible to combine several functionalities in a single carrier, silica-based materials are excellent candidates for biomedical applications. However, the functionality of the nanoparticles can get lost upon exposure to biological media due to uncontrolled biomolecule adsorption. Therefore, it is important to develop strategies that reduce non-specific protein-particle interactions without losing the introduced surface functionality. Herein, organosilane chemistry is employed to produce magnetic silica nanoparticles bearing differing amounts of amino and alkene functional groups on their surface as orthogonally addressable chemical functionalities. Simultaneously, a short-chain zwitterion is added to decrease the non-specific adsorption of biomolecules on the nanoparticles surface. The multifunctional particles display reduced protein adsorption after incubation in undiluted fetal bovine serum as well as in single protein solutions (serum albumin and lysozyme). Besides, the particles retain their capacity to selectively react with biomolecules. Thus, they can be covalently bio-functionalized with an antibody by means of orthogonal click reactions. These features make the described multifunctional silica nanoparticles a promising system for the study of surface interactions with biomolecules, targeting, and bio-sensing.