Guidelines for the experimental design of pharmacokinetic studies with nanomaterials in preclinical animal models

Effects of Commonly used Surfactants, Poloxamer 188 and Tween 80, on the Drug Transport Capacity of Intestinal Glucose Transporters

Some glycoside drugs can be transported through intestinal glucose transporters (IGTs). The surfactants used in oral drug preparations can affect the function of transporter proteins. This study aimed to investigate the effect of commonly used surfactants, Poloxamer 188 and Tween 80, on the drug transport capacity of IGTs. Previous studies have shown that gastrodin is the optimal drug substrate for IGTs. Gastrodin was used as a probe drug to evaluate the effect of these two surfactants on intestinal absorption in SD rats through pharmacokinetic and in situ single-pass intestinal perfusion. Then, the effects of the two surfactants on the expression of glucose transporters and tight-junction proteins were examined using RT-PCR and western blotting. Additionally, the effect of surfactants on intestinal permeability was evaluated through hematoxylin-eosin staining. The results found that all experimental for Poloxamer 188 (0.5%, 2.0% and 8.0%) and Tween 80 (0.1% and 2.0%) were not significantly different from those of the blank group. However, the AUC(0-∞) of gastrodin increased by approximately 32% when 0.5% Tween 80 was used. The changes in IGT expression correlated with the intestinal absorption of gastrodin. A significant increase in the expression of IGTs was observed at 0.5% Tween 80. In conclusion, Poloxamer 188 had minimal effect on the drug transport capacity of IGTs within the recommended limits of use. However, the expression of IGTs increased in response to 0.5% Tween 80, which significantly enhanced the drug transport capacity of IGTs. However, 0.1% and 2.0% Tween 80 had no significant effect.

Quantitative Pharmacokinetics Reveal Impact of Lipid Composition on Microbubble and Nanoprogeny Shell Fate

Microbubble-enabled focused ultrasound (MB-FUS) has revolutionized nano and molecular drug delivery capabilities. Yet, the absence of longitudinal, systematic, quantitative studies of microbubble shell pharmacokinetics hinders progress within the MB-FUS field. Microbubble radiolabeling challenges contribute to this void. This barrier is overcome by developing a one-pot, purification-free copper chelation protocol able to stably radiolabel diverse porphyrin-lipid-containing Definity® analogues (pDefs) with >95% efficiency while maintaining microbubble physicochemical properties. Five tri-modal (ultrasound-, positron emission tomography (PET)-, and fluorescent-active) [64 Cu]Cu-pDefs are created with varying lipid acyl chain length and charge, representing the most prevalently studied microbubble compositions. In vitro, C16 chain length microbubbles yield 2-3x smaller nanoprogeny than C18 microbubbles post FUS. In vivo, [64 Cu]Cu-pDefs are tracked in healthy and 4T1 tumor-bearing mice ± FUS over 48 h qualitatively through fluorescence imaging (to characterize particle disruption) and quantitatively through PET and γ-counting. These studies reveal the impact of microbubble composition and FUS on microbubble dissolution rates, shell circulation, off-target tissue retention (predominantly the liver and spleen), and FUS enhancement of tumor delivery. These findings yield pharmacokinetic microbubble structure-activity relationships that disrupt conventional knowledge, the implications of which on MB-FUS platform design, safety, and nanomedicine delivery are discussed.

Recent advancements on in vitro blood-brain barrier model: A reliable and efficient screening approach for preclinical and clinical investigation

INTRODUCTION

The efficiency of brain therapeutics is greatly hindered by the blood-brain barrier (BBB). BBB's protective function, selective permeability, and dynamic functionality maintain the harmony between the brain and peripheral region. Thus, the design of any novel drug carrier system requires the complete study and investigation of BBB permeability, efflux transport, and the effect of associated cellular and non-vascular unit trafficking on BBB penetrability. The in vitro BBB models offer a most promising, and reliable mode of initial investigation of BBB permeability and associated factors as strong evidence for further preclinical and clinical investigation.

AREA COVERED

This review work covers the structure and functions of BBB components and different types of in vitro BBB models along with factors affecting BBB model development and model selection criteria.

EXPERT OPINION

In vivo models assume to reciprocate the physiological environment to the maximum extent. However, the interspecies variability, NVUs trafficking, dynamic behavior of BBB, etc., lead to non-reproducible results. The in vitro models are comparatively less complex, and flexible, as per the study design, could generate substantial evidence and help identify suitable in vivo animal model selection.

Strain differences in the drug transport capacity of intestinal glucose transporters in Sprague-Dawley versus Wistar rats, C57BL/6J versus Kunming mice

Designing oral drug delivery systems using intestinal glucose transporters (IGTs) may be one of the strategies for improving oral bioavailability of drugs. However, little is known about the biological factors affecting the drug transport capacity of IGTs. Gastrodin is a sedative drug with a structure very similar to glucose. It is a highly water-soluble phenolic glucoside. It can hardly enter the intestine through simple diffusion but exhibits good oral bioavailability of over 80%. We confirmed that gastrodin is absorbed via the intestinal glucose transport pathway. It has the highest oral bioavailability among the reported glycosides' active ingredients through this pathway. Thus, gastrodin is the most selective drug substrate of IGTs and can be used to evaluate the drug transport capacity of IGTs. Obviously, strain is one of the main biological factors affecting drug absorption. This study firstly compared the drug transport capacity of IGTs between SD rats and Wistar rats and between C57 mice and KM mice by pharmacokinetic experiments and single-pass intestinal perfusion experiments of gastrodin. Then, the sodium-dependent glucose transporter type 1 (SGLT1) and sodium-independent glucose transporters type 2 (GLUT2) in the duodenum, jejunum, ileum and colon of these animals were quantified using RT-qPCR and Western blot. The results showed that the oral bioavailability of gastrodin in Wistar rats was significantly higher than in SD rats and significantly higher in KM mice than in C57 mice. Gastrodin absorption significantly differed among different intestinal segments in SD rats, C57 mice and KM mice, except Wistar rats. RT-qPCR and Western blot demonstrated that the intestinal expression distribution of SGLT1 and GLUT2 in SD rats and C57 mice was duodenum ≈ jejunum > ileum > colon. SGLT1 expression did not differ among different intestinal segments in KM mice, whereas the intestinal expression distribution of GLUT2 was duodenum ≈ jejunum ≈ ileum > colon. However, the expression of SGLT1 and GLUT2 did not differ among different intestinal segments in Wistar rats. It was reported that the intestinal expression distribution of SGLT1 and GLUT2 in humans is duodenum > jejunum > ileum > colon. Hence, the intestinal expression distribution of SGLT1 and GLUT2 of SD rats and C57 mice was more similar to that in humans. In conclusion, the drug transport capacity of IGTs differs in different strains of rats and mice. SD rats and C57 mice are more suitable for evaluating the pharmacokinetics of glycosides' active ingredients absorbed via the intestinal glucose transport pathway.

Smart Nanosystems for Overcoming Multiple Biological Barriers in Cancer Nanomedicines Transport: Design Principles, Progress, and Challenges

The development of smart nanosystems, which could overcome diverse biological barriers of nanomedicine transport, has received intense scientific interest in improving the therapeutic efficacies of traditional nanomedicines. However, the reported nanosystems generally hold disparate structures and functions, and the knowledge of involved biological barriers is usually scattered. There is an imperative need for a summary of biological barriers and how these smart nanosystems conquer biological barriers, to guide the rational design of the new-generation nanomedicines. This review starts from the discussion of major biological barriers existing in nanomedicine transport, including blood circulation, tumoral accumulation and penetration, cellular uptake, drug release, and response. Design principles and recent progress of smart nanosystems in overcoming the biological barriers are overviewed. The designated physicochemical properties of nanosystems can dictate their functions in biological environments, such as protein absorption inhibition, tumor accumulation, penetration, cellular internalization, endosomal escape, and controlled release, as well as modulation of tumor cells and their resident tumor microenvironment. The challenges facing smart nanosystems on the road heading to clinical approval are discussed, followed by the proposals that could further advance the nanomedicine field. It is expected that this review will provide guidelines for the rational design of the new-generation nanomedicines for clinical use.

Role of Nanomaterials in the Fabrication of bioNEMS/MEMS for Biomedical Applications and towards Pioneering Food Waste Utilisation

bioNEMS/MEMS has emerged as an innovative technology for the miniaturisation of biomedical devices with high precision and rapid processing since its first R&D breakthrough in the 1980s. To date, several organic including food waste derived nanomaterials and inorganic nanomaterials (e.g., carbon nanotubes, graphene, silica, gold, and magnetic nanoparticles) have steered the development of high-throughput and sensitive bioNEMS/MEMS-based biosensors, actuator systems, drug delivery systems and implantable/wearable sensors with desirable biomedical properties. Turning food waste into valuable nanomaterials is potential groundbreaking research in this growing field of bioMEMS/NEMS. This review aspires to communicate recent progress in organic and inorganic nanomaterials based bioNEMS/MEMS for biomedical applications, comprehensively discussing nanomaterials criteria and their prospects as ideal tools for biomedical devices. We discuss clinical applications for diagnostic, monitoring, and therapeutic applications as well as the technological potential for cell manipulation (i.e., sorting, separation, and patterning technology). In addition, current in vitro and in vivo assessments of promising nanomaterials-based biomedical devices will be discussed in this review. Finally, this review also looked at the most recent state-of-the-art knowledge on Internet of Things (IoT) applications such as nanosensors, nanoantennas, nanoprocessors, and nanobattery.

Toxicokinetics, dose-response, and risk assessment of nanomaterials: Methodology, challenges, and future perspectives

The rapid growth of nanomaterial applications has raised safety concerns for human health. A number of studies have been conducted to assess the toxicokinetics, toxicology, dose-response, and risk assessment of different nanomaterials using in vitro and in vivo animal and human models. However, current studies cannot meet the demand for efficient assessment of toxicokinetics, dose-response relationships, or the toxicological risk arising from the rapidly increasing number of newly synthesized nanomaterials. In this article, we review the methods for conducting toxicokinetics, hazard identification, dose-response, exposure, and risk assessment studies of nanomaterials, identify the knowledge gaps, and discuss the challenges remaining. We provide the rationale behind the appropriate design of nanomaterial plasma toxicokinetic and tissue distribution studies, including caveats on the interpretation and correlation of in vitro and in vivo toxicology studies. The potential of using physiologically based pharmacokinetic (PBPK) models to extrapolate toxicokinetic and toxicity findings from in vitro to in vivo and from animals to humans is discussed, and the knowledge gaps of PBPK modeling for nanomaterials are identified. While challenges still exist, there has been progress in the toxicokinetics, hazard identification, and risk assessment of nanomaterials in the past two decades. Recent advancements in the field are highlighted with relevant examples. We also share latest guidelines as well as our perspectives on future studies needed to characterize the toxicokinetics, toxicity, and dose-response relationship in support of nanomaterial risk assessment. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

FRET as the tool for in vivo nanomedicine tracking

Advanced drug delivery system utilizing a nanocarrier is the major application of nanotechnology on pharmacotherapeutics. However, despite the promising benefits and a leading trend in pharmaceutical research, nanomedicine development suffers from a poor clinical translation problem as only a handful of nanomedicine products reach the market yearly. The conventional pharmacokinetic study generally focuses only on monitoring the level of a free drug but ignores the nanocarrier's role in pharmacokinetics. One hurdle is that it is difficult to directly track intact nanocarriers in vivo to explore their pharmacokinetics. Although several imaging techniques such as radiolabeling, nuclear imaging, fluorescence imaging, etc., have been developed over the past few years, currently, one method that can successfully track the intact nanocarriers in vivo directly is by Förster resonance energy transfer (FRET). This review summarizes the application of FRET as the in vivo nanoparticle tracker for studying the in vivo pharmacokinetics of the organic nanocarriers and gives elaborative details on the techniques utilized.

Nanosafety: An Evolving Concept to Bring the Safest Possible Nanomaterials to Society and Environment

The use of nanomaterials has been increasing in recent times, and they are widely used in industries such as cosmetics, drugs, food, water treatment, and agriculture. The rapid development of new nanomaterials demands a set of approaches to evaluate the potential toxicity and risks related to them. In this regard, nanosafety has been using and adapting already existing methods (toxicological approach), but the unique characteristics of nanomaterials demand new approaches (nanotoxicology) to fully understand the potential toxicity, immunotoxicity, and (epi)genotoxicity. In addition, new technologies, such as organs-on-chips and sophisticated sensors, are under development and/or adaptation. All the information generated is used to develop new in silico approaches trying to predict the potential effects of newly developed materials. The overall evaluation of nanomaterials from their production to their final disposal chain is completed using the life cycle assessment (LCA), which is becoming an important element of nanosafety considering sustainability and environmental impact. In this review, we give an overview of all these elements of nanosafety.

Pharmacokinetic Variability in Pre-Clinical Studies: Sample Study with Abiraterone in Rats and Implications for Short-Term Comparative Pharmacokinetic Study Designs

One of the major concerns for all in vivo experiments is intra- and inter-subject variability, which can be a great source of inaccuracy. The aim of this study is, therefore, to estimate the ability of parallel vs. cross-over design studies in order to describe the relative pharmacokinetic performance of the studied drug formulations. We analyzed the data from a drug development program that examined the performance of innovative abiraterone acetate formulations against the identical reference product in three stages. In stages 1–3, groups A–F were dosed with the reference product once in a parallel manner. Stage 4 was performed to evaluate the intra-individual variability (IIV) by repeated administration of the reference product to the same animals. Although the geometric mean (90% CI) values of abiraterone AUC_last in groups A–F were similar to the IIV group (24.36 (23.79–41.00) vs. 26.29 (20.56–47.00) mg/mL·min·g), the results generated in the isolated parallel groups provided imprecise estimates of the true AUC_last values ranging from 9.62 to 44.62 mg/mL·min·g due to chance. Notably, in 4 out of 15 possible pair comparisons between the parallel groups, the confidence intervals did not include 100%, which is the true ratio for all comparisons tested after identical formulation administration to all groups. A cross-over design can significantly improve the methodology in short-term comparative pre-clinical pharmacokinetic studies, and can provide more precise and accurate results in comparison to more traditional pre-clinical study designs.

Pharmacokinetics, Tissue Distribution, and Human Serum Albumin Binding Properties of Delicaflavone, a Novel Anti-Tumor Candidate

Delicaflavone (DF), a natural active ingredient from Selaginella doederleinii Hieron, has been reported to have favorable anticancer effects and is thus considered a potential anticancer agent. However, its pharmacokinetics and plasma protein binding properties remain unknown. Here, we investigated the pharmacokinetic profile of DF in rats using a validated HPLC-MS/MS methods, as well as its human serum albumin (HSA) binding properties through multi-spectroscopic and in silico methods. The results showed that DF was rapidly eliminated and had a widespread tissue distribution after intravenous administration. DF showed linear dynamics in the dose range of 30–60 mg/kg and poor oral bioavailability. The major distribution tissues of DF were the liver, lungs, and kidneys. Ultraviolet and fluorescence spectroscopy and molecular docking demonstrated that DF had a static quenching effect on HSA, with one binding site, and relatively strong binding constants. Thermodynamic analysis of the binding data revealed that hydrogen bonding and van der Waals interactions played major roles in binding. The results of this study further our understanding of the pharmacokinetic and plasma protein binding properties of the potential anticancer agent DF and shed light on pharmacological strategies that may be useful for the development of novel cancer therapeutics.

NIR-activated self-sensitized polymeric micelles for enhanced cancer chemo-photothermal therapy

NIR-activated therapies based on light-responsive drug delivery systems are emerging as a remote-controlled method for cancer precise therapy. In this work, fluorescent dye indocyanine green (ICG)-conjugated and bioactive compound gambogic acid (GA)-loaded polymeric micelles (GA@PEG-TK-ICG PMs) were smoothly fabricated via the self-assembly of the reactive oxygen species (ROS)-responsive thioketal (TK)-linked amphiphilic polymer poly(ethyleneglycol)-thioketal-(indocyanine green) (PEG-TK-ICG). The resultant micelles demonstrated increased resistance to photobleaching, enhanced photothermal conversion efficiency, NIR-controlled drug release behavior, preferable biocompatibility, and excellent tumor accumulation performance. Moreover, upon an 808 nm laser irradiation, the micellar photoactive chromophore ICG converted the absorbed optical energy to both hyperthermia for photothermal therapy (PTT) and ROS as the feedback trigger to the micelles for the tumor-specific release of GA, which could serve as not only a chemotherapeutic drug to directly kill tumor cells but also a heat shock protein 90 (HSP90) inhibitor to realize the photothermal sensitization. As a result, an extremely high tumor inhibition rate (97.9%) of mouse 4 T1 breast cancer models was achieved with negligible side effects after the chemo-photothermal synergistic therapy. This NIR-activated nanosystem with photothermal self-sensitization function may provide a feasible option for the effective treatment of aggressive breast cancers.

Organosilica colloids as nitric oxide carriers: Pharmacokinetics and biocompatibility

Nitric oxide (NO) is a potential therapeutic agent for various diseases. However, it is challenging to deliver this unstable, free-radical gaseous molecule in the body. Various nanoparticle-based drug delivery systems have been investigated as promising NO carriers without detailed characterization of their biological fate. The purpose of this study is to investigate the pharmacokinetics and biocompatibility of organosilica-based NO-delivering nanocarriers. Two distinct NO nanoformulations, namely NO-SiNP-1 and NO-SiNP-2, were prepared from a thiol-functionalized organosilane using nanoprecipitation and direct aqueous synthesis, respectively. During the preparation, the thiol group was converted to S-nitrosothiol (SNO) under a nitrosation condition. The final products contain SNO-loaded organosilica particles of similar sizes (~130 nm), but of different morphologies and surface charges (between the two formulations). In the in vitro release kinetics study, NO-SiNP-1 exhibited a much slower NO release rate than NO-SiNP-2 (by 5-fold); therefore, the former is considered as a slow NO releaser, and the latter a fast NO releaser. However, in the rat pharmacokinetic study (IV bolus of 50 μmol/kg), NO-SiNP-1 was rapidly eliminated from the blood (within 20 min); in contrast, NO-SiNP-2 was slowly eliminated with an extended circulation time of 12 h for plasma SNO, along with markedly higher plasma levels of nitrite and nitrate. The two formulations are generally biocompatible. In conclusion, the paper presents contrast biological fates of two organosilica colloidal formulations for nitric oxide delivery.

Blood-brain barrier models: Rationale for selection

Brain delivery is a broad research area, the outcomes of which are far hindered by the limited permeability of the blood-brain barrier (BBB). Over the last century, research has been revealing the BBB complexity and the crosstalk between its cellular and molecular components. Pathologically, BBB alterations may precede as well as be concomitant or lead to brain diseases. To simulate the BBB and investigate options for drug delivery, several in vitro, in vivo, ex vivo, in situ and in silico models are used. Hundreds of drug delivery vehicles successfully pass preclinical trials but fail in clinical settings. Inadequate selection of BBB models is believed to remarkably impact the data reliability leading to unsatisfactory results in clinical trials. In this review, we suggest a rationale for BBB model selection with respect to the addressed research question and downstream applications. The essential considerations of an optimal BBB model are discussed.

Can Natural Products Exert Neuroprotection without Crossing the Blood-Brain Barrier?

The scope of evidence on the neuroprotective impact of natural products has been greatly extended in recent years. However, a key question that remains to be answered is whether natural products act directly on targets located in the central nervous system (CNS), or whether they act indirectly through other mechanisms in the periphery. While molecules utilized for brain diseases are typically bestowed with a capacity to cross the blood–brain barrier, it has been recently uncovered that peripheral metabolism impacts brain functions, including cognition. The gut–microbiota–brain axis is receiving increasing attention as another indirect pathway for orally administered compounds to act on the CNS. In this review, we will briefly explore these possibilities focusing on two classes of natural products: omega-3 polyunsaturated fatty acids (n-3 PUFAs) from marine sources and polyphenols from plants. The former will be used as an example of a natural product with relatively high brain bioavailability but with tightly regulated transport and metabolism, and the latter as an example of natural compounds with low brain bioavailability, yet with a growing amount of preclinical and clinical evidence of efficacy. In conclusion, it is proposed that bioavailability data should be sought early in the development of natural products to help identifying relevant mechanisms and potential impact on prevalent CNS disorders, such as Alzheimer’s disease.