The efficient and selective delivery of therapeutic drugs to the target site remains the main obstacle in the development of new drugs and therapeutic interventions. Up until today, nanomicelles have shown their prospective as nanocarriers for drug delivery owing to their small size, good biocompatibility, and capacity to effectively entrap lipophilic drugs in their core. Nanomicelles are formed via self-assembly in aqueous media of amphiphilic molecules into well-organized supramolecular structures. Molecular weights and structure of the core and corona forming blocks are important properties that will determine the size of nanomicelles and their shape. Selective delivery is achieved via novel design of various stimuli-responsive nanomicelles that release drugs based on endogenous or exogenous stimulations such as pH, temperature, ultrasound, light, redox potential, and others. This review summarizes the emerging micellar nanocarriers developed with various designs, their outstanding properties, and underlying principles that grant targeted and continuous drug delivery. Finally, future perspectives, and challenges for nanomicelles are discussed based on the current achievements and remaining issues.
Novel multiple emitting amphiphilic conjugated polythiophene‐coated CdTe quantum dots for picogram level determination of the 2,4,6‐trinitrophenol (TNP) explosive are developed. Four biocompatible sensors, cationic polythiophene nanohybrids (CPTQDs), nonionic polythiophene nanohybrids (NPTQDs), anionic polythiophene nanohybrids (APTQDs), and thiophene copolymer nanohybrids (TCPQDs), are designed using an in situ polymerization method, which shows highly enhanced fluorescence intensity and quantum yield (up to 78%). All sensors are investigated for nitroexplosive detection to provide a remarkable fluorescence quenching for TNP and the quenching efficiency reached 96% in the case of TCPQDs. The fluorescence of the sensors are quenched by TNP through inner filter effect, electrostatic, π−π, and hydrogen bonding interactions. Under optimal conditions, the detection limits of CPTQDs, NPTQDs, APTQDs, and TCPQDs are 2.56, 7.23, 4.12, and 0.56 × 10−9
m, respectively, within 60 s. More importantly, portable, cost effective, and simple to use paper strips and chitosan film are successfully applied to visually detect as little as 2.29 pg of TNP. The possibility of utilizing a smartphone with a color‐scanning APP in the determination of TNP is also established. Moreover, the practical application of the developed sensors for TNP detection in tap and river water samples is described with satisfactory recoveries of 98.02−107.50%.
Urea is an important indicator for health, environmental, and energy applications worldwide. Various analytics have been developed to detect urea rapidly and selectively for real-world interfacing; however, they still suffer from noise fluctuations due to environmental and instrumental conditions because most analytics are based on a single-signal readout system. In this study, we designed and synthesized a dual-signal, fluorometric and colorimetric, and read-out assay that integrates fluorescent carbon dot (CD) nanosensors with pH-responsive plasmonic silver nanoparticles (Ag NPs) for urea detection. The urease enzyme can specifically hydrolyze urea to generate carbon dioxide and ammonia, causing an increase in the pH, which activates the reduction affinity of tannic acid to generate plasmonic Ag NPs in situ. In situ generation of plasmonic Ag NPs is enabled by the reduction affinity of tannic acid, which is activated when the pH rises as a result of the urease enzyme hydrolyzing urea to produce carbon dioxide and ammonia. The absorption spectra of the Ag NPs overlapped closely with the fluorescence spectrum of the CDs, enabling effective quenching of the CD fluorescence upon urea exposure. This fluorogenic and chromogenic dual signal is used to quantify the accurate urea concentrations, showing a limit of detection (LOD) of 18 nM and 1.05 μM for fluorometric and colorimetric sensing within linear ranges between 100 nM−1 mM and 50 μM−1 mM, respectively�the lowest recorded LOD among fluorometric or colorimetric sensors. In addition, the dual sensor showed reliable detection of urea in real urine samples with (96−102.5%) recoveries. Finally, the dual-signal nanosensor was successfully implanted in the hydrogel matrix to facilitate a solid-state stable signal readout with an LOD of 287 nM. This dual-sensor construct provides fundamental solutions for nanomaterials in reliable and accurate urea detection applications that accelerate real-world interfacing.
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