Chemical Amplifier Research Articles

Chemical Amplification-Enabled Topological Modification of Nucleic Acid Aptamers for Enhanced Cancer-Targeted Theranostics.

Site-specific chemical conjugation has long been a challenging endeavor in the field of ligand-directed modification to produce homogeneous conjugates for precision medicine. Here, we develop a chemical amplification-enabled topological modification (Chem-ATM) methodology to establish a versatile platform for the programmable modification of nucleic acid aptamers with designated functionalities. Differing from conventional conjugation strategies, a three-dimensional artificial base is designed in Chem-ATM as a chemical amplifier, giving access to structurally and functionally diversified conjugation of aptamers, with precise control over loading capacity but in a sequence-independent manner. Meanwhile, the sp3 hybridized atom-containing amplifier enables planar-to-stereo conformational transformation of the entire conjugate, eliciting high steric hindrance against enzymatic degradation in complex biological environments. The versatility of Chem-ATM is successfully demonstrated by its delivery of anticancer drugs and imaging agents for enhanced therapy and high-contrast noninvasive tumor imaging in xenograft and orthotopic tumor models. This study offers a different perspective for ligand-directed chemical conjugation to enrich the molecular toolbox for bioimaging and drug development.

Characteristics of O3 Production in the Western Suburb of Hefei in Summer Based on the Observation of Total Peroxy Radical

In August 2020, the observations of total peroxy radical concentrations were carried out in the western suburb site of Hefei using a peroxy radical chemical amplifier (PERCA) instrument. The ozone production and its sensitivity were characterized with the measured O3 and its precursors. The results showed that the daily variation in total peroxy radical concentrations exhibited an obvious convex tend, with the highest value at approximately 12:00; the average peak peroxy radical concentration was 43.8×10-12; and the concentrations of the peroxy radical and ozone were driven by strong solar radiation and high temperature. The photochemical ozone production rate could be determined with peroxy radical and NO concentration. The average ozone peak production rate in summer was 10.6×10-9 h-1, which was more sensitive to NO concentration. Based on the ratio of the radical loss rate due to reactions with NOx to the radical loss rate (Ln/Q), the characteristics of O3 production in the western suburb of Hefei in summer were analyzed. The results showed that O3 production sensitivity varied greatly during the day. The summer O3 production regime shifted from the VOC-sensitive chemistry in the early morning to NOx-sensitive chemistry in the afternoon, and this regime transition typically occurred in the morning.

Highly sensitive acetylcholine biosensing via chemical amplification of enzymatic processes in nanochannels.

Acetylcholinesterase-modified nanochannels are proposed as reliable and reproducible nanofluidic sensors for highly sensitive detection of acetylcholine. The operation mechanism relies on the use of weak polyelectrolytes as "chemical amplifiers" that adjust/reconfigure the nanochannel surface charge in the presence of local pH changes induced by the enzymatic reaction. Experimental results show that the presence of acetylcholine can be transduced into measurable ionic signals with a low limit of detection.

Effect of hydrogen enrichment on the flame propagation, emissions formation and energy balance of the natural gas spark ignition engine

Technically, using hydrogen in the natural gas (NG) will increase the combustion rate of the spark ignition (SI) engine, particularly at the lean burn condition, which also benefits to improve the thermal efficiency and combustion efficiency. The aim of this study was to investigate the effect of hydrogen addition on the flame propagation, emissions formation, energy balance and the relationships between exhaust emissions and mediate species during the flame propagation in the natural gas (NG) SI engine. The 1D and 3D simulation models of the NG SI engine were built and validated against with experimental data. The results indicated that the initial spark kernel volume of the NG SI engine with hydrogen addition was larger than that of without hydrogen enriched. The NO concentration increased with the hydrogen due to its higher peak combustion temperature. The NO emission mainly generated inside the flame front, where located in the high temperature combustion zone. In addition, the CO formation rate of the NG SI engine with the hydrogen addition was faster and oxidized more completely. With adding hydrogen in natural gas, the amount of H and OH were significantly increased due to the chemical amplifiers, thereby enhancing the radical pool. The HC and soot emissions of the NG SI engine were much lower with the hydrogen addition. Furthermore, the energy efficiency and fuel economy of the NG SI engine were improved with the hydrogen addition, particularly at the lean mixture conditions.

Dilution gas and hydrogen enrichment on the laminar flame speed and flame structure of the methane/air mixture

In this study, the mechanisms of the chemical, thermal and dilution effects of the CO2, H2O, N2 and EGR quantitatively analyzed on the laminar flame speed, laminar flame structure and key radicals profiles of the premixed methane/air mixture. Moreover, the artificial species of the FCO2, FH2O, FN2 and FEGR were used to separate the combined chemical and physical effects. Furthermore, the impacts of the hydrogen enrichment coupled with the EGR on the laminar flame speed, the laminar flame structure and key radicals profiles of the premixed methane/air mixture was also studied in detailed. The results indicated that the chemical effect of the CO2 dilution gas produced the greatest impacts on the laminar flame speed, adiabatic combustion temperature and key radicals formation of the methane/air, and followed by the H2O vapor, EGR and N2. In addition, the dilution limitation of the CO2 in the methane/air was smallest, followed by the H2O vapor, EGR and N2. Moreover, the thermal effect of the CO2 in the methane/air was strongest due to its highest specific heat capacity, followed by the H2O vapor, EGR and N2. The laminar flame speed and adiabatic combustion temperature of the methane/hydrogen/air increased with increasing the hydrogen. Furthermore, the lean-burn limitation of the methane/air was extended with the increase of the hydrogen. The radical pool, such as H, O, OH, accelerated the chain branching reactions and the chain propagation reactions, and thereby increasing the effect of the chemical amplifier during the combustion of the premixed methane/air mixture.

Dynamic Complex Emulsions as Amplifiers for On-Chip Photonic Cavity-Enhanced Resonators.

Despite the recent emergence of microcavity resonators as label-free biological and chemical sensors, practical applications still require simple and robust methods to impart chemical selectivity and reduce the cost of fabrication. We introduce the use of hydrocarbon-in-fluorocarbon-in-water (HC/FC/W) double emulsions as a liquid top cladding that expands the versatility of optical resonators as chemical sensors. The all-liquid complex emulsions are tunable droplets that undergo dynamic and reversible morphological transformations in response to a change in the chemical environment (e.g., exposure to targeted analytes). This chemical-morphological coupling drastically modifies the effective refractive index, allowing the complex emulsions to act as a chemical transducer and signal amplifier. We detect this large change in the refractive index by tracking the shift of the enveloped resonant spectrum of a silicon nitride (Si3N4) racetrack resonator-based sensor, which correlates well with a change in the morphology of the complex droplets. This combination of soft materials (dynamic complex emulsions) and hard materials (on-chip resonators) provides a unique platform for liquid-phase, real-time, and continuous detection of chemicals and biomolecules for miniaturized and remote, environmental, medical, and wearable sensing applications.

Characterization of a chemical amplifier for peroxy radical measurements in the atmosphere

Peroxy radicals (HO2 and RO2) are key species in atmospheric chemistry. They are produced during the oxidation of volatile organic compounds (VOCs) and are involved in the formation of photochemical pollutants such as ozone (O3) and secondary organic aerosols (SOA). However, ambient measurements of these reactive species are still challenging and only a few techniques can achieve both a good selectivity and a detection limit that is low enough for ambient measurements. In this publication we present the characterization of a Chemical Amplifier (CA) using two different approaches for ambient measurements of peroxy radicals, including the PEroxy Radical Chemical Amplifier (PERCA) and the Ethane based CHemical AMPlification (ECHAMP). At 50% Relative Humidity (RH), the experimental Chain Length (CL) for PERCA was found to be higher by approximately a factor of 3.7 compared to ECHAMP. The RH-dependence of the CL was also found to be larger for PERCA by a factor of 1.12. Box modeling of the chemistry taking place in the instrument highlighted that the formation of HNO3 from the HO2+NO reaction has a strong impact on the CL for both approaches. In addition, experiments conducted to quantify the RO2–to-HO2 conversion efficiency for a large range of organic peroxy radicals confirmed that it mainly depends on the organic nitrate (RONO2) formation yield, while the alkyl nitrite (RONO) yield is not limiting the CL in most cases. Ambient measurements using the PERCA approach are shown to illustrate the performances of this new instrument.

Peroxy radical measurements by ethane – nitric oxide chemical amplification and laser-induced fluorescence during the IRRONIC field campaign in a forest in Indiana

Abstract. Peroxy radicals were measured in a mixed deciduous forest atmosphere in Bloomington, Indiana, USA, during the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) during the summer of 2015. Total peroxy radicals ([XO2]≡[HO2]+Σ[RO2]) were measured by a newly developed technique involving chemical amplification using nitric oxide (NO) and ethane (C2H6) followed by NO2 detection by cavity-attenuated phase-shift spectroscopy (hereinafter referred to as ECHAMP – Ethane CHemical AMPlifier). The sum of hydroperoxy radicals (HO2) and a portion of organic peroxy radicals ([HO2*]=[HO2]+Σαi[RiO2], 0<α<1) was measured by the Indiana University (IU) laser-induced fluorescence–fluorescence assay by gas expansion instrument (LIF-FAGE). Additional collocated measurements include concentrations of NO, NO2, O3, and a wide range of volatile organic compounds (VOCs) and meteorological parameters. XO2 concentrations measured by ECHAMP peaked between 13:00 and 16:00 local time (LT), with campaign average concentrations of 41±15 ppt (1σ) at 14:00 LT. Daytime concentrations of isoprene averaged 3.6±1.9 ppb (1σ), whereas average concentrations of NOx ([NO] + [NO2]) and toluene were 1.2 and 0.1 ppb, respectively, indicating a low impact from anthropogenic emissions at this site. We compared ambient measurements from both instruments and conducted a calibration source comparison. For the calibration comparison, the ECHAMP instrument, which is primarily calibrated with an acetone photolysis method, sampled the output of the LIF-FAGE calibration source which is based on the water vapor photolysis method and, for these comparisons, generated a 50 %–50 % mixture of HO2 and either butane or isoprene-derived RO2. A bivariate fit of the data yields the relation [XO2]ECHAMP=(0.88±0.02;[HO2]+[RO2])IU_cal+(6.6±4.5) ppt. This level of agreement is within the combined analytical uncertainties for the two instruments' calibration methods. A linear fit of the daytime (09:00–22:00 LT) 30 min averaged [XO2] ambient data with the 1 min averaged [HO2*] data (one point per 30 min) yields the relation [XO2]=(1.08±0.05)[HO2*]-(1.4±0.3). Day-to-day variability in the [XO2]/[HO2*] ratio was observed. The lowest [XO2]/[HO2*] ratios between 13:00 and 16:00 LT were 0.8 on 13 and 18 July, whereas the highest ratios of 1.1 to 1.3 were observed on 24 and 25 July – the same 2 d on which the highest concentrations of isoprene and ozone were observed. Although the exact composition of the peroxy radicals during IRRONIC is not known, zero-dimensional photochemical modeling of the IRRONIC dataset using two versions of the Regional Atmospheric Chemistry Mechanism (RACM2 and RACM2-LIM1) and the Master Chemical Mechanism (MCM 3.2 and MCM 3.3.1) all predict afternoon [XO2]/[HO2*] ratios of between 1.2 and 1.5. Differences between the observed ambient [XO2]/[HO2*] ratio and that predicted with the 0-D modeling can be attributed to deficiencies in the model, errors in one of the two measurement techniques, or both. Time periods in which the ambient ratio was less than 1 are definitely caused by measurement errors (including calibration differences), as such ratios are not physically meaningful. Although these comparison results are encouraging and demonstrate the viability in using the new ECHAMP technique for field measurements of peroxy radicals, further research investigating the overall accuracy of the measurements and possible interferences from both methods is warranted.

Characterization of ozone production in San Antonio, Texas, using measurements of total peroxy radicals

Abstract. Observations of total peroxy radical concentrations ([XO2] ≡ [RO2] + [HO2]) made by the Ethane CHemical AMPlifier (ECHAMP) and concomitant observations of additional trace gases made on board the Aerodyne Mobile Laboratory (AML) during May 2017 were used to characterize ozone production at three sites in the San Antonio, Texas, region. Median daytime [O3] was 48 ppbv at the site downwind of central San Antonio. Higher concentrations of NO and XO2 at the downwind site also led to median daytime ozone production rates (P(O3)) of 4.2 ppbv h−1, a factor of 2 higher than at the two upwind sites. The 95th percentile of P(O3) at the upwind site was 15.1 ppbv h−1, significantly lower than values observed in Houston. In situ observations, as well as satellite retrievals of HCHO and NO2, suggest that the region was predominantly NOx-limited. Only approximately 20 % of observations were in the VOC-limited regime, predominantly before 11:00 EST, when ozone production was low. Biogenic volatile organic compounds (VOCs) comprised 55 % of total OH reactivity at the downwind site, with alkanes and non-biogenic alkenes responsible for less than 10 % of total OH reactivity in the afternoon, when ozone production was highest. To control ozone formation rates at the three study sites effectively, policy efforts should be directed at reducing NOx emissions. Observations in the urban center of San Antonio are needed to determine whether this policy is true for the entire region.

Principles and Applications of Nucleic Acid Strand Displacement Reactions.

Dynamic DNA nanotechnology, a subfield of DNA nanotechnology, is concerned with the study and application of nucleic acid strand-displacement reactions. Strand-displacement reactions generally proceed by three-way or four-way branch migration and initially were investigated for their relevance to genetic recombination. Through the use of toeholds, which are single-stranded segments of DNA to which an invader strand can bind to initiate branch migration, the rate with which strand displacement reactions proceed can be varied by more than 6 orders of magnitude. In addition, the use of toeholds enables the construction of enzyme-free DNA reaction networks exhibiting complex dynamical behavior. A demonstration of this was provided in the year 2000, in which strand displacement reactions were employed to drive a DNA-based nanomachine (Yurke, B.; et al. Nature 2000, 406, 605-608). Since then, toehold-mediated strand displacement reactions have been used with ever increasing sophistication and the field of dynamic DNA nanotechnology has grown exponentially. Besides molecular machines, the field has produced enzyme-free catalytic systems, all DNA chemical oscillators and the most complex molecular computers yet devised. Enzyme-free catalytic systems can function as chemical amplifiers and as such have received considerable attention for sensing and detection applications in chemistry and medical diagnostics. Strand-displacement reactions have been combined with other enzymatically driven processes and have also been employed within living cells (Groves, B.; et al. Nat. Nanotechnol. 2015, 11, 287-294). Strand-displacement principles have also been applied in synthetic biology to enable artificial gene regulation and computation in bacteria. Given the enormous progress of dynamic DNA nanotechnology over the past years, the field now seems poised for practical application.

Fog geoengineering to abate local ozone pollution at ground level by enhancing air moisture

High concentrations of ozone (O3) at ground level in urban and industrial regions worldwide have long been a major air pollution issue, notably during daytime because sunlights induce the photochemical production of ozone. After a review of actual techniques to clean O3 pollution in urban and industrial regions, I present a fog geoengineering scheme for abating ozone pollution at ground level by enhancing ambient moisture locally through spraying water mist into the atmosphere. This scheme is based on my results showing that ozone levels decrease with air relative humidity. For instance, the mean O3 concentrations decrease from 70.0 to 21.2 ppbv when relative humidity increases from below 40% to more than 80%, in Hangzhou city at midday times (11:00–16:00) without precipitation, during the “ozone season” from May to October of 2017. The mechanism of fog geoengineering is that atmosphere moisture inhibits O3 formation by lowering air temperature, decreasing the chain length of peroxy radical chemical amplifiers (HO2, RO2, and RC(O)O2), and decreasing the chain length of NO2 by enhancing particle water, and destroys the existing O3 photo-chemically by water vapor through catalytic O3 destruction cycle. Ozone mitigation by fog geoengineering has several advantages such as being a nature-like process, quick response, technological feasibility, efficacy, relatively low cost, and cooling effects. The proposed fog geoengineering to decrease the local O3 at ground level could potentially be on avenue for addressing heavy O3 pollution during the hot summer in megacities globally as expected.

Chemical Tools for Targeted Amplification of Reactive Oxygen Species in Neutrophils.

A number of chemical compounds are known, which amplify the availability of reactive oxygen species (ROS) in neutrophils both in vitro and in vivo. They can be roughly classified into NADPH oxidase 2 (NOX2)-dependent and NOX2-independent reagents. NOX2 activation is triggered by protein kinase C agonists (e.g., phorbol esters, transition metal ions), redox mediators (e.g., paraquat) or formyl peptide receptor (FPR) agonists (e.g., aromatic hydrazine derivatives). NOX2-independent mechanisms are realized by reagents affecting glutathione homeostasis (e.g., l-buthionine sulfoximine), modulators of the mitochondrial respiratory chain (e.g., ionophores, inositol mimics, and agonists of peroxisome proliferator-activated receptor γ) and chemical ROS amplifiers [e.g., aminoferrocene-based prodrugs (ABPs)]. Since a number of inflammatory and autoimmune diseases, as well as cancer and bacterial infections, are triggered or enhanced by aberrant ROS production in neutrophils, it is tempting to use ROS amplifiers as drugs for the treatment of these diseases. However, since the known reagents are not cell specific, their application for treatment likely causes systemic enhancement of oxidative stress, leading to severe side effects. Cell-targeted ROS enhancement can be achieved either by using conjugates of ROS amplifiers with ligands binding to receptors expressed on neutrophils (e.g., the GPI-anchored myeloid differentiation marker Ly6G or FPR) or by designing reagents activated by neutrophil function [e.g., phagocytic activity or enzymatic activity of neutrophil elastase (NE)]. Since binding of an artificial ligand to a receptor may trigger or inhibit priming of neutrophils the latter approach has a smaller potential for severe side effects and is probably better suitable for therapy. Here, we review current approaches for the use of ROS amplifiers and discuss their applicability for treatment. As an example, we suggest a possible design of neutrophil-specific ROS amplifiers, which are based on NE-activated ABPs.

Simple and Ultrasensitive Chemically Amplified Electrochemical Detection of Ferrocenemethanol on 4-Nitrophenyl Grafted Glassy Carbon Electrode

Chemically amplified electrochemical detection, redox-active probe being amplified its electrochemical anodic current by a sacrificial electron donor presenting in solution, holds great potential for simple and quantitative bioanalytical analysis. Herein, we report the chemically amplified electrochemical analysis that drastically enhanced a detection of ferrocenemethanol (analyte) by ferrocyanide (chemical amplifier) on 4-nitrophenyl grafted glassy carbon electrodes at 60°C. The glassy carbon electrode grafted with a 4-nitrophenyl group using an electrochemical reduction suppressed the oxidation of ferrocyanide and thus enabled detection of ferrocenemethanol with excellent selectivity. The ferrocenemethanol was detected down to an nM range using a linear sweep voltammetry under kinetically optimized conditions. The detection limit was improved by decreasing the concentration of the ferrocyanide and increasing temperature. Keywords: Chemically amplified electrochemical detection, Ferrocenemethanol, Ferrocyanide, Nanomolar electrochemical detection, 4-nitrophenyl grafted glassy carbon electrode

Ethane-Based Chemical Amplification Measurement Technique for Atmospheric Peroxy Radicals

Peroxy radicals play important roles in the atmospheric oxidation of organic compounds and the formation of ozone and secondary organic aerosol. There are few peroxy radical measurement techniques; the most common, chemical amplification using CO and NO, requires the use of toxic reagents, and its calibration factor is very sensitive to relative humidity. We present a new method for quantifying atmospheric peroxy radicals, ECHAMP (Ethane CHemical AMPlifier). Sampled air is mixed with NO and C2H6 (rather than CO), effecting a series of reactions that ultimately produces 25 molecules of NO2 per sampled peroxy radical under dry conditions. This “amplification” factor decreases to 17 at a relative humidity of 50%, yielding a 1σ precision for 90 s average measurements of 0.8–2.5 ppt depending on the atmospheric variability of ozone. We demonstrated the utility of the new technique with measurements in Bloomington, IN, in July 2015.

Chemical amplification--cavity attenuated phase shift spectroscopy measurements of atmospheric peroxy radicals.

We describe a new instrument for the quantification of atmospheric peroxy radicals (HO2, CH3O2, C2H5O2, etc.) using the chemical amplification method. Peroxy radicals are mixed with high concentrations of NO and CO, causing a chain reaction that produces a measurable increase in NO2 which is quantified by cavity attenuated phase shift (CAPS) spectroscopy, a highly sensitive spectroscopic detection technique. The instrument utilizes two identical reaction chambers, each with a dedicated CAPS NO2 sensor. Similar to all dual-channel chemical amplifiers, one reaction chamber operates in amplification or "ROx" mode and the other in background or "Ox" mode. The peroxy radical mixing ratio is determined by the difference between the two channels' NO2 readings divided by a laboratory-determined chain length. Each reaction chamber alternates between ROx and Ox mode on an anti-synchronized schedule, eliminating the effect of CAPS baseline offsets on the calculated peroxy radical concentrations. The chain length is determined by a new calibration method: peroxyacetyl and methyl peroxy radicals are produced by the photolysis of acetone and quantified as NO2 following reaction with excess NO. We demonstrate the performance of the instrument with results from ambient sampling in Amherst and several diagnostics of its precision. The detection limit while sampling ambient air at a relative humidity (RH) of 40% is 0.6 ppt (1 min average, signal-to-noise ratio =2), with an estimated accuracy of 25% (2σ).

Charged nanoparticles crystallizing and controlling crystallization: from coatings to nanoparticle surfactants to chemical amplifiers

Metal nanoparticles functionalized with self-assembled monolayers of ligands terminated in charged groups constitute a unique class of nanoscopic polyions – or “nanoions” in short – capable of assembling into higher-order structures.

An Enzymatic Chemical Amplifier Based on Mechanized Nanoparticles

A chemical amplifier was constructed based on enzyme-encapsulated mesoporous silica nanoparticles. By employing a supramolecular nanogate assembly that is capable of controlling the access to the encapsulated enzyme, selectivity toward substrate sizes is enabled. When an analyte molecule actuates the mechanical nanogate and exposes the enzymes, a catalytic production of fluorescent molecules is initiated. This study demonstrates a new concept of self-amplification of a chemical sensing process and can potentially increase the detection sensitivity.

Chemical amplifier and energy utilization principles of heat conversion cycle systems

A new concept, which is named as a chemical amplifier or CHC (chemical heat converter), was proposed to analyze the heat conversion cycle systems and its application in system innovation. This new concept primarily comprises a pair of reversible reactions, an endothermic and an exothermic reaction, which occur in the liquid–gas or solid–gas phase. By introducing the heat flux of high-temperature input and low-temperature output to meet the reactions, the CHC cycle produces two types of work capacities, wA* and wR*, which respectively employ the working fluid for the heat engine and the heat pump as carriers. These wok capacities can be used either separately or together when coupling with a heat engine sub-cycle and/or a heat pump sub-cycle, and the different heat conversion mechanisms in five kinds of heat conversion configurations were revealed using the proposed concept. And then to show a full application example of the CHC concept, an absorption power/cooling cogeneration cycle with working fluid difluoromethane and N,N-dimethylformamide was analyzed. This research exhibited that both the benefits of the increasing of expansion work in the heat engine sub-cycle and the reduction of work consumption for compression in the heat pump sub-cycle can be obtained through the work abilities output by the CHC which is driven by mid-low grade heat.

Diel peroxy radicals in a semi-industrial coastal area: nighttime formation of free radicals

Abstract. Peroxy radicals were measured by a PeRCA (Peroxy Radical Chemical Amplifier) instrument in the boundary layer during the DOMINO (Diel Oxidant Mechanisms In relation to Nitrogen Oxides) campaign at a coastal, forested site influenced by urban-industrial emissions in southern Spain in late autumn. Total peroxy radicals (RO2* = HO2 + ΣRO2) generally showed a daylight maximum between 10 and 50 pptv at 13:00 UTC, with an average of 18 pptv over the 15 days of measurements. Emissions from the industrial area of Huelva often impacted the measurement site at night during the campaign. The processing of significant levels of anthropogenic organics leads to an intense nocturnal radical chemistry accompanied by formation of organic peroxy radicals at comparable levels to those of summer photochemical conditions with peak events up to 60–80 pptv. The RO2 production initiated by reactions of NO3 with organic trace gases was estimated to be significant, but not sufficient to account for the concentrations of RO2* observed in air masses carrying high pollutant loading. The nocturnal production of peroxy radicals in those periods seems therefore to be dominated by ozonolysis of volatile organic compounds, in particular alkenes of industrial petrochemical origin. RO2* diurnal variations were consistent with HO2 measurements available at the site. HO2/RO2* ratios generally varied between 0.3 and 0.6, though on some occasions this ratio was likely to have been affected by instrumental artifacts (overestimated HO2) associated with high RO2 loads.

An enzyme-responsive system programmed for the double release of bioactive molecules through an intracellular chemical amplification process

The rise of chemical biology has led to the development of sophisticated molecular devices designed to explore and manipulate biological processes. Within this framework, we developed the first chemical system programmed for the selective internalization and subsequent enzyme-catalyzed double release of bioactive compounds inside a targeted population of cells. This system is composed of five distinct units including a targeting ligand, an enzymatic trigger, a self-immolative linker and two active compounds articulated around a chemical amplifier. Designed as such, this molecular assembly is capable in an autonomous manner to recognize a selected population of cells, penetrate into the intracellular medium through endocytosis and transform a single enzymatic activation step into the release of two active units. Demonstrating that an enzyme-catalyzed amplification process can occur spontaneously under the conditions prevailing within the cells could be an important step toward the development of innovative molecular systems for a diverse range of applications spanning drug delivery, biological sensors and diagnostics.