Drug Delivery Monitoring Research Articles

Fluorescence resonance energy transfer monitoring of pH-responsive doxorubicin release from carbon dots/aptamer functionalized magnetic mesoporous silica.

Aim: To develop a novel theranostic nanoplatform for simultaneous fluorescent monitoring and stimuli-triggered drug delivery. Materials & methods: Different microscopic and spectroscopic techniques were used for the characterization of nanocarriers. MCF-7 and human umbilical vein endothelial cell lines were cultured and treated with different doses of doxorubicin-loaded nanocarriers. The cell viability and drug release were studied using MTT assay and fluorescence microscopy. Results: Biocompatible and mono-disperse nanocarriers represent hollow and mesoporous structures with the calculated surface area of 552.83m2.g-1, high magnetic activity (12.6 emu.g-1), appropriate colloidal stability and high drug loading capacity (up to 61%). Conclusion: Taxane-based carbon dots act as the pH-responsive gatekeepers for the controlled release of doxorubicin into cancer cells and provide a fluorescence resonance energy transfer system for real-time monitoring of drug delivery.

Stimuli‐Responsive Nanotheranostics

Stimuli‐Responsive Nanotheranostics

Conjugated Polymer Nanoparticles Based on Copper Coordination for Real-Time Monitoring of pH-Responsive Drug Delivery.

Metal coordination-driven composite systems have excellent stability and pH-responsive ability, making them suitable for specific drug delivery in physiological conditions. In this study, an anionic conjugated polymer PPEIDA with a poly(p-phenylene ethynylene) backbone and iminodiacetic acid (IDA) side chains is used as a drug carrier to construct a class of pH-responsive nanoparticles, PPEIDA-Cu-DOX conjugated polymer nanoparticles (CPNs), by taking advantage of the metal coordination interaction of Cu2+ with PPEIDA and the drug doxorubicin (DOX). PPEIDA-Cu-DOX CPNs have high drug loading and encapsulation efficiency (EE), calculated to be 54.30 ± 1.10 and 95.80 ± 0.84%, respectively. Due to the good spectral overlap, Förster resonance energy transfer (FRET) takes place between PPEIDA and the drug DOX, which enables the observation of the loading and the release of DOX from CPNs in an acidic environment by monitoring fluorescence emission changes. Therefore, PPEIDA-Cu-DOX CPNs can also be used in real-time cell imaging to monitor drug release in addition to delivering DOX targeting tumor cells. Compared with free DOX, PPEIDA-Cu-DOX CPNs show a similar inhibition to tumor cells and lower toxicity to normal cells. Our results demonstrate the feasibility and potential of constructing pH-responsive CPNs via metal-ligand coordination interactions for cancer treatment.

Dual-dye systems comprising activatable fluorescein dye and hydrophobic or hydrophilic Cy5 reference fluorophore for ratiometric drug delivery monitoring

Ratiometric fluorescence detection in biological samples in vitro and in vivo mitigates several issues in conventional single-signal measurements such as light absorption and scattering, dye photobleaching, and instrumental parameters. Herein, two new systems for ratiometric monitoring of drug delivery are synthesized and investigated. These systems comprise a non-fluorescent fluorescein-based dye, Flu, bound to the anticancer drug, azatoxin (Aza), through a hydrolytically cleavable acrylate ester linker and either hydrophobic (Cy5h) or hydrophilic (Cy5s) pentamethine cyanine dye providing a red-light reference signal. Upon drug release, the green Flu fluorescence notably increases enabling ratiometric tracking of drug release events. The spectral properties of the developed conjugates and fluorescently monitored drug release rates are investigated in biologically relevant media with respect of the Cy5 dye hydrophilicity.

Nanocarriers of Eu<sup>3+</sup> doped silica nanoparticles modified by APTES for luminescent monitoring of cloxacillin

<abstract> <p>Drug nanocarriers have been continuously improved to promote satisfactory release control. In this sense, luminescent materials have become an alternative option in clinical trials due to their ability to monitor drug delivery. Among the nanocarriers, silica stands out for structural stability, dispersibility, and surface reactivity. When using ceramic nanocarriers, one of the challenges is their interaction and selectivity capability for organic molecules, such as drugs. In order to overcome such adversity, superficial modifications can be carried out to enable a higher affinity for the desired drug. Thus, the present study aimed to obtain silica nanoparticles (NPs) doped with low concentrations of europium (III) superficially modified by (3-aminopropyl)triethoxysilane (APTES) to assess their interaction with the model drug cloxacillin benzathine. This drug was chosen because it is part of the ampicillin family and is commonly used in several treatments. Near-spherical and homogeneous silica NPs were obtained via sol-gel synthesis, with particle sizes of approximately 21 nm. It was possible to verify the fluorescence capacity of the silica NPs when doped with europium (III) in a mole percent that varied from 0.5 to 3.0%. A 10% volume percent of APTES caused the silica nanoparticles to increase the degree of hydrophobicity, with a shift in the contact angle from 8° to 51°. After surface modification by APTES, the silica nanocarrier (10 g·L<sup>-1</sup>) achieved a satisfactory degree of CLOX incorporation (25 g·L<sup>-1</sup>), increasing the adsorptive capacity to values above 50%. Therefore, silica NPs doped with europium (III) in a low percent of 0.5% (mole) modified by APTES showed promising results as an alternative option for trials and clinical studies of drug incorporation.</p> </abstract>

Microfluidic Assisted Flash Precipitation of Photocrosslinkable Fluorescent Organic Nanoparticles for Fine Size Tuning and Enhanced Photoinduced Processes.

Highly concentrated dispersions of fluorescent organic nanoparticles (FONs), broadly used for optical tracking, bioimaging and drug delivery monitoring, are obtained using a newly designed micromixer chamber involving high impacting flows. Fine size tuning and narrow size distributions are easily obtained by varying independently the flow rates of the injected fluids and the concentration of the dye stock solution. The flash nanoprecipitation process employed herein is successfully applied to the fabrication of bicomposite FONs designed to allow energy transfer. Considerable enhancement of the emission signal of the energy acceptors is promoted and its origin is found to result from polarity rather than steric effects. Finally, we exploit the high spatial confinement encountered in FONs and their ability to encapsulate hydrophobic photosensitizers to induce photocrosslinking. An increase in the photocrosslinked FON stiffness is evidenced by measuring the elastic modulus at the nanoscale using atomic force microscopy. These results pave the way toward the straightforward fabrication of multifunctional and mechanically photoswitchable FONs, opening novel opportunities in sensing, multimodal imaging, and theranostics.

Passive acoustic mapping utilizing compressed-domain processing for real-time monitoring of cavitation-enhanced drug delivery

Ultrasound-induced cavitation has been shown to improve the delivery of a range of therapeutics including small-molecule drugs, oncolytic viruses and immunotherapies, potentially enhancing their delivery and reducing their toxicity for treatment of solid tumours. Real-time monitoring methods such as passive acoustic mapping (PAM) may be employed to map cavitation activity during treatment. However, while advances in acquisition hardware facilitate outstanding monitoring capability, transfer, storage and processing of the resulting data remains a challenge. Previously we investigated the use of compressed sensing (CS) techniques to sparsely reconstruct full-rate time-series array data for subsequent conventional PAM. Here we extend this approach to directly perform PAM using the compressed-domain (or CS) data. In our approach the CS data is obtained from projections that jointly compress the full-rate array data. The PAM image is computed directly from the CS data using a sparse matching pursuit algorithm, with a dictionary formed from a discretized model using a reference sensor. Results showing accurate localization of cavitation activity using CS-PAM are obtained with simulated and in-vivo (porcine) measured data but processing only 1% of the full-rate data. Finally, common issues with voxel grid density that affect source localization in CS-PAM and conventional PAM are highlighted.

Comparison of photoacoustic and fluorescence tomography for the in vivo imaging of ICG-labelled liposomes in the medullary cavity in mice

Few reports quantitatively compare the performance of photoacoustic tomography (PAT) versus fluorescence molecular tomography (FMT) in vivo. We compared both modalities for the detection of signals from injected ICG liposomes in the tibial medullary space of 10 BALB/c mice in vivo and ex vivo. Signals significantly correlated between modalities (R² = 0.69) and within each modality in vivo versus ex vivo (PAT: R² = 0.70, FMT: R² = 0.76). Phantom studies showed that signals at 4 mm depth are detected down to 3.3 ng ICG by PAT and 33 ng by FMT, with a nominal spatial resolution below 0.5 mm in PAT and limited to 1 mm in FMT. Our study demonstrates comparable in vivo sensitivity, but superior ex vivo sensitivity and in vivo resolution for our ICG liposomes of the VevoLAZR versus the FMT2500. PAT provides a useful new tool for the high-resolution imaging of bone marrow signals, for example for monitoring drug delivery.

Imaging With Therapeutic Acoustic Wavelets-Short Pulses Enable Acoustic Localization When Time of Arrival is Combined With Delay and Sum.

Passive acoustic mapping (PAM) is an algorithm that reconstructs the location of acoustic sources using an array of receivers. This technique can monitor therapeutic ultrasound procedures to confirm the spatial distribution and amount of microbubble activity induced. Current PAM algorithms have an excellent lateral resolution but have a poor axial resolution, making it difficult to distinguish acoustic sources within the ultrasound beams. With recent studies demonstrating that short-length and low-pressure pulses-acoustic wavelets-have the therapeutic function, we hypothesized that the axial resolution could be improved with a quasi-pulse-echo approach and that the resolution improvement would depend on the wavelet's pulse length. This article describes an algorithm that resolves acoustic sources axially using time of flight and laterally using delay-and-sum beamforming, which we named axial temporal position PAM (ATP-PAM). The algorithm accommodates a rapid short pulse (RaSP) sequence that can safely deliver drugs across the blood-brain barrier. We developed our algorithm with simulations (k-wave) and in vitro experiments for one-, two-, and five-cycle pulses, comparing our resolution against that of two current PAM algorithms. We then tested ATP-PAM in vivo and evaluated whether the reconstructed acoustic sources mapped to drug delivery within the brain. In simulations and in vitro, ATP-PAM had an improved resolution for all pulse lengths tested. In vivo, experiments in mice indicated that ATP-PAM could be used to target and monitor drug delivery into the brain. With acoustic wavelets and time of flight, ATP-PAM can locate acoustic sources with a vastly improved spatial resolution.

Internally Responsive Nanomaterials for Activatable Multimodal Imaging of Cancer.

Advances in technology and nanomedicine have led to the development of nanoparticles that can be activated for multimodal imaging of cancer, where a stimulus induces a material modification that enhances image contrast. Multimodal imaging using nanomaterials with this capability can combine the advantages and overcome the limitations of any single imaging modality. When designed with stimuli-responsive abilities, the target-to-background ratio of multimodal imaging nanoprobes increases because specific stimuli in the tumor enhance the signal. Several aspects of the tumor microenvironment can be exploited as an internal stimulus response for multimodal imaging applications, such as the pH gradient, redox processes, overproduction of various enzymes, or combinations of these. In this review, design strategies are discussed and an overview of the recent developments of internally responsive multimodal nanomaterials is provided. Properly implementing this approach improves noninvasive cancer diagnosis and staging as well as provides a method to monitor drug delivery and treatment response.

Synthesis and characterization of proanthocyanidin-chitosan nanoparticles: An assessment on human colorectal carcinoma HT-29 cells

Cancer nanotheranostic materials are helpful in monitoring drug delivery and efficacy against tumor cells. Current chemotherapeutic may have adverse side effects and this necessity to discover the new modern therapeutic nano-drugs. In the present study, we designed the new targeted and degradable polymer of bio-active chitosan nanoparticles with proanthocyanidin (PAC-CSNPs) and evaluated its apoptotic effects against human colorectal carcinoma cells (HT-29). The functional groups were characterized by Fourier-transform infrared spectroscopy and transmission electron microscope. Further, their dispersion of spherical form nanoparticle with an average size of 73.43 nm used for drug delivery system. The PAC-CSNPs were targeted to inhibit the cyclin-dependent kinases and prevent cell cycle/cell division in cancer cells. At high concentrations of PAC (25 μg/mL) exposure, cell viability of HT-29 cells was greater than 80%. However, at low concentrations of PAC-CSNPs (6.25 μg/mL) exposure, HT-29 cell mortality was high, which may be due to the efficient drug release by CSNPs. The percentage of reactive oxygen species (ROS) levels were 12 ± 2.52% (control), 39 ± 4.32% (PAC), and 85.06 ± 3.54% (PAC-CSNPs). The over production of ROS by PAC-CSNPs can prompt DNA damage, cell death and apoptosis in HT-29 cells. The in vivo toxicity of synthesized PAC-CSNPs was tested against zebra fish observed at dose-time-dependent intervals. In conclusion, the PAC-CSNPs enhanced HT-29 cell death and shows promise as a novel future nano-therapy for cancer.

Hybrid and Passive Tissue-Anchoring Mechanism for Ingestible Resident Devices

This work presents a hybrid tissue-anchoring mechanism that combines a pre-compressed microspring for autonomous actuation and a barbed microneedle (MN) for robust tissue anchoring with minimized preloading. The springmicroneedle unit (SMU) allows facile integration with potential ingestible resident systems to enable prolonged operation in the gastrointestinal (GI) tract (e.g. biomarker monitoring and therapeutic drug delivery). Utilizing high-precision direct laser writing (DLW), the SMU is directly fabricated on a flexible polyimide substrate, which that can be conveniently attached onto the exterior packages of ingestible devices to reduce the form factor and therefore to save room for multifunctional system components. The 3-D printed microspring can be compressed and embedded within a thin layer of dissolvable polymer (polyethylene glycol) and autonomously actuated with a ~140-μm displacement upon polymer dissolution in aqueous media at 37°C. Mechanical calibration of the SMU demonstrated an average release force of 8 mN for a 100-μm actuation. According to our previous research into barbed MNs, this actuation force provides a large enough preload for a MN to achieve robust tissue-anchoring. Above all, the novel and effective tissue-anchoring mechanism has a great potential for enabling long-term operation of miniature biosensing and drug delivery systems. [2020-0169].

Optical Projection Tomography Using a Commercial Microfluidic System.

Optical projection tomography (OPT) is the direct optical equivalent of X-ray computed tomography (CT). To obtain a larger depth of field, traditional OPT usually decreases the numerical aperture (NA) of the objective lens to decrease the resolution of the image. So, there is a trade-off between sample size and resolution. Commercial microfluidic systems can observe a sample in flow mode. In this paper, an OPT instrument is constructed to observe samples. The OPT instrument is combined with commercial microfluidic systems to obtain a three-dimensional and time (3D + T)/four-dimensional (4D) video of the sample. “Focal plane scanning” is also used to increase the images’ depth of field. A series of two-dimensional (2D) images in different focal planes was observed and compared with images simulated using our program. Our work dynamically monitors 3D OPT images. Commercial microfluidic systems simulate blood flow, which has potential application in blood monitoring and intelligent drug delivery platforms. We design an OPT adaptor to perform OPT on a commercial wide-field inverted microscope (Olympusix81). Images in different focal planes are observed and analyzed. Using a commercial microfluidic system, a video is also acquired to record motion pictures of samples at different flow rates. To our knowledge, this is the first time an OPT setup has been combined with a microfluidic system.

Improved Biosafety and Transdermal Delivery of Aconitine via Diethylene Glycol Monoethyl Ether-Mediated Microemulsion Assisted with Microneedles.

In the current study, diethylene glycol monoethyl ether-mediated microemulsions were combined with microneedles for enhanced transdermal aconitine delivery. The oil-in-water microemulsion increasedaconitine solubility and enhanced transdermal drug delivery and assistance with metal microneedles enhanced permeation of the aconitine-loaded microemulsion. Carried by the microemulsion, the in vitro permeability of aconitine was significantly enhanced, and further improved using microneedles. In vivo microdialysis revealed that the subcutaneous local drug concentration reached a high level within 30 min and remained relatively consistent to the end of the experimental period. AUC0-t of the microemulsion group was significantly higher than that of the aqueous solution group, and the microemulsion combined with microneedles group achieved the highest AUC0-t among the tested groups. The microemulsion and microdialysis probe also showed good biocompatibility with skin tissue. The microemulsion could be internalized by HaCaT and CCC-ESF-1 cells via lysosomes. The in vitro cytotoxicity of aconitine toward skin cells was reduced via encapsulation by microemulsion, and the prepared microemulsion developed no skin irritation. Hence, transdermal aconitine delivery and drug biosafety were effectively improved by loading into the microemulsion and assisting with microneedles, and in vivo microdialysis technique is suitable for realtime monitoring of transdermal drug delivery with microemulsion-based drug vehicles.

Transition Metal-Based Prodrugs for Anticancer Drug Delivery.

Transition metal complexes, of which the platinum(II) complex cisplatin is an example, have been used in medicine to treat cancer for more than 40 years. Although many successes have been achieved, there are problems associated with the use of these drugs, such as side effects and drug resistance. Converting them into prodrugs, to make them more inert, so that they can travel to the tumour site unchanged and release the drug in its active form only there, is a strategy which is the subject of much research nowadays. The new prodrugs may be activated and release the cytotoxic agent by differences in oxygen concentration or in pH, by the action of overexpressed enzymes, by differences in metabolic rates, etc., which characteristically distinguish cancer cells from normal ones, or even by the input of radiation, which can be visible light. Converting a metal complex into a prodrug may also be used to improve its pharmacological properties. In some cases, the metal complex is a carrier which transports the active drug as a ligand. Some platinum prodrugs have reached clinical trials. So far platinum, ruthenium and cobalt have been the most studied metals. This review presents the recent developments in this area, including the types of complexes used, the mechanisms of drug action and in some cases the techniques applied to monitor drug delivery to cells.

Multiplexed non-invasive tumor imaging of glucose metabolism and receptor-ligand engagement using dark quencher FRET acceptor.

Rationale: Following an ever-increased focus on personalized medicine, there is a continuing need to develop preclinical molecular imaging modalities to guide the development and optimization of targeted therapies. Near-Infrared (NIR) Macroscopic Fluorescence Lifetime Förster Resonance Energy Transfer (MFLI-FRET) imaging offers a unique method to robustly quantify receptor-ligand engagement in live intact animals, which is critical to assess the delivery efficacy of therapeutics. However, to date, non-invasive imaging approaches that can simultaneously measure cellular drug delivery efficacy and metabolic response are lacking. A major challenge for the implementation of concurrent optical and MFLI-FRET in vivo whole-body preclinical imaging is the spectral crowding and cross-contamination between fluorescent probes.Methods: We report on a strategy that relies on a dark quencher enabling simultaneous assessment of receptor-ligand engagement and tumor metabolism in intact live mice. Several optical imaging approaches, such as in vitro NIR FLI microscopy (FLIM) and in vivo wide-field MFLI, were used to validate a novel donor-dark quencher FRET pair. IRDye 800CW 2-deoxyglucose (2-DG) imaging was multiplexed with MFLI-FRET of NIR-labeled transferrin FRET pair (Tf-AF700/Tf-QC-1) to monitor tumor metabolism and probe uptake in breast tumor xenografts in intact live nude mice. Immunohistochemistry was used to validate in vivo imaging results.Results: First, we establish that IRDye QC-1 (QC-1) is an effective NIR dark acceptor for the FRET-induced quenching of donor Alexa Fluor 700 (AF700). Second, we report on simultaneous in vivo imaging of the metabolic probe 2-DG and MFLI-FRET imaging of Tf-AF700/Tf-QC-1 uptake in tumors. Such multiplexed imaging revealed an inverse relationship between 2-DG uptake and Tf intracellular delivery, suggesting that 2-DG signal may predict the efficacy of intracellular targeted delivery.Conclusions: Overall, our methodology enables for the first time simultaneous non-invasive monitoring of intracellular drug delivery and metabolic response in preclinical studies.

Fluorescent Reporters for Drug Delivery Monitoring

AbstractMonitoring of drug delivery is an essential technique for innovative medical treatments, including cancer therapy. Fluorescence imaging has become an important tool in tracking drug delivery and thus improving treatment efficacy. Binding fluorescent reporters to therapeutic agents paves the way to real time monitoring of drug delivery and drug distribution in vitro and in vivo. This review discusses fluorescent reporters used in drug delivery monitoring and provides an overview of recent achievements in the development of fluorescence based drug delivery systems.

All-in-one theranostic nanoplatform with controlled drug release and activated MRI tracking functions for synergistic NIR-II hyperthermia-chemotherapy of tumors

Real-time tracking drug release behavior is fundamentally important for avoiding adverse effects or unsuccessful treatment in personalize medical treatment. However, the development of a non-invasive drug reporting platform still remains challenging. Herein the design of a novel synthetic magnetic resonance imaging (MRI) agent for drug release tracking (SMART) is reported, which integrates photothermal core and paramagnetic ion/drug loading shell with a thermal valve in a hybrid structure. Through near-infrared (NIR)-II photothermal effect originating from inner Au-Cu9S5 nanohybrid core, burst release of drugs loaded in the mesoporous silica shell is achieved. The concomitant use of a phase change material not only prevents premature drug release, but also regulates heating effect, keeping local temperature below 45 °C, enabling synergistic chemotherapy and mild hyperthermia in vitro and in vivo. Furthermore, the drug release from SMART facilitates proton accessibility to the paramagnetic ions anchored inside mesopores channels, enhancing longitudinal T1 relaxation rate and displaying positive signal correlation to the amount of released drug, thus allowing non-invasive real-time monitoring of drug release event. The current study highlights the potential of designed MRI nanophores such as SMART for real-time and in-situ monitoring of drug delivery for precision theranostic applications.

Hyperstar Polyester‐Based Functional Nanotheranostics for the Targeted Drug Delivery and Treatment of Cancer

AbstractIn this study, we have synthesized new class of hyperstar polyester (HSPE) polymer using a functional A2B monomer and bio‐based sorbitol. We hypothesize that by incorporating sorbitol, its amphiphilic nature will give the polymer greater solubility and allow for the encapsulation of wide range of anti‐cancer therapeutics. We used potassium methoxide to catalyze the melt polymerization reaction. Using the solvent diffusion method, this polymer was used to construct polymeric nanoparticles to encapsulate therapeutics, in one step, for monitoring drug delivery and treatment. The cytotoxicity of our HSPE nanoparticles was evaluated by a cell‐based MTT assays using prostate cancer cells (LNCaP) and healthy cells (CHO). In addition, the level of internalization of our HSPE nanoparticles was evaluated using fluorescence microscopy. Results showed the HSPE nanoparticles have the capability to target and concurrently image and kill cancer cells. Taken together, these studies indicate the successful development of a new drug delivery system and demonstrated its potential use in the pharmaceutical industry and the field of medicine.

Peptide-Driven Targeted Drug-Delivery System Comprising Turn-On Near-Infrared Fluorescent Xanthene-Cyanine Reporter for Real-Time Monitoring of Drug Release.

Targeted drug delivery (TDD) is an efficient strategy for cancer treatment. However, the real-time monitoring of drug delivery is still challenging because of a pronounced lack of TDD systems capable of providing a near-infrared (NIR) fluorescence signal for the detection of drug-release events. Herein, a new TDD system, comprising a turn-on NIR fluorescent reporter attached to an anticancer drug and targeting peptide, is reported. This system provides both TDD and NIR fluorescence monitoring of drug-release events in target tissue. In this TDD system, a new carboxy-derivatized xanthene-cyanine (XCy) dye is attached to an anticancer drug, chlorambucil (CLB), through a hydrolytically cleavable ester linker and coupled to a targeting peptide, octreotide amide (OCTA), which is specific to somatostatin receptors SSTR-2 and STTR-5 overexpressed on many tumor cells. This OCTA-G-XCy-CLB (G: γ-aminobutyric acid) conjugate exhibits no detectable fluorescence, whereas, upon the hydrolytic cleavage of the ester linker, a bright NIR fluorescence appears at λ≈710 nm; this signals release of the drug. Real-time TDD monitoring is demonstrated for the example of the human pancreatic cancer cell line overexpressing SSTR-2 and STTR-5, in comparison with the noncancerous Chinese hamster ovary cell line, which contains a reduced number of these receptors.