The ability to efficiently deliver a drug to a tumor site is dependent on a wide range of physiologically imposed design constraints. Nanotechnology provides the possibility of creating delivery vehicles where these design constraints can be decoupled, allowing new approaches for reducing the unwanted side effects of systemic delivery, increasing targeting efficiency and efficacy. Here we review the design strategies of the two FDA-approved antibody-drug conjugates (Brentuximab vedotin and Trastuzumab emtansine) and the four FDA-approved nanoparticle-based drug delivery platforms (Doxil, DaunoXome, Marqibo, and Abraxane) in the context of the challenges associated with systemic targeted delivery of a drug to a solid tumor. The lessons learned from these nanomedicines provide important insight into the key challenges associated with the development of new platforms for systemic delivery of anti-cancer drugs.
The ability to efficiently deliver a drug or gene to a tumor site is dependent on a wide range of factors including circulation time, interactions with the mononuclear phagocyte system, extravasation from circulation at the tumor site, targeting strategy, release from the delivery vehicle, and uptake in cancer cells. Nanotechnology provides the possibility of creating delivery systems where the design constraints are decoupled, allowing new approaches for reducing the unwanted side effects of systemic delivery, increasing tumor accumulation, and improving efficacy. The physico-chemical properties of nanoparticle-based delivery platforms introduce additional complexity associated with pharmacokinetics, tumor accumulation, and biodistribution. To assess the impact of nanoparticle-based delivery systems, we first review the design strategies and pharmacokinetics of FDA-approved nanomedicines. Next we review nanomedicines under development, summarizing the range of nanoparticle platforms, strategies for targeting, and pharmacokinetics. We show how the lack of uniformity in preclinical trials prevents systematic comparison and hence limits advances in the field.
A field-effect transistor-based cortisol sensor was demonstrated in physiological conditions. An antibody-embedded polymer on the remote gate was proposed to overcome the Debye length issue (λ). The sensing membrane was made by linking poly(styrene- co-methacrylic acid) (PSMA) with anticortisol before coating the modified polymer on the remote gate. The embedded receptor in the polymer showed sensitivity from 10 fg/mL to 10 ng/mL for cortisol and a limit of detection (LOD) of 1 pg/mL in 1× PBS where λ is 0.2 nm. A LOD of 1 ng/mL was shown in lightly buffered artificial sweat. Finally, a sandwich ELISA confirmed the antibody binding activity of antibody-embedded PSMA.
Doxil, a liposomal formulation of the chemotherapeutic drug doxorubicin, is FDA-approved for multiple indications. Doxil liposomes are designed to retain doxorubicin in circulation, minimize clearance by the mononuclear phagocyte system, and limit uptake in healthy tissue. Although pharmacokinetic data and survival statistics from clinical trials provide insight into distribution and efficacy, many details of the mechanism of action remain unresolved, despite the importance in translating liposome-based drug delivery systems to other molecules and cargo. Therefore, the objective of this study is to quantitatively assess the kinetics of doxorubicin leakage from Doxil liposomes. In contrast to previous studies, we consider three processes: dissolution of solid doxorubicin, protonation/deprotonation of soluble doxorubicin, and passive transport of neutral doxorubicin across the lipid bilayer of the liposomes. Experiments were performed for Doxil, Doxil-like liposomes, and Doxil-like liposomes with reduced cholesterol and pegylation. To mimic physiological conditions, we also performed experiments in serum and under slightly acidic conditions at pH5. We show that crystalline doxorubicin dissolution can be described by a first order rate constant of 1.0×10cms at 37°C. Doxorubicin leakage can be described by first order rate constant for transport across the lipid bilayer with values in the range from 1 to 3×10cms at 37°C. Based on these results we discuss implications for the mechanism of action, taking Doxil pharmacokinetics into account.
Systemic drug delivery to a solid tumor involves a sequence of steps that determine efficacy and survival. Extravasation from circulation at the tumor site is a critical step in this sequence since it regulates how much of the drug accumulates in the tumor. Despite its importance in determining outcomes, extravasation from circulation remains a “black box.” The objective of this study is to develop predictive tools for optimization of drug delivery systems. By comparing pharmacokinetics of liposomal doxorubicin in tumor-free and tumor bearing mice we quantitatively assess the rate constants for distribution, elimination, and tumor accumulation. We then relate these rate constants to the tumor-type and drug delivery system. We compare tumor accumulation in three tumor types and show a 10-fold difference between a colorectal adenocarcinoma and a pancreatic adenocarcinoma. Finally, we show how quantitative predictions of changes in tumor accumulation can be used to optimize drug delivery systems.
Organic field-effect transistor (OFET)-based biosensors with antibody receptors are widely considered for protein antigen detection. To the authors' knowledge, there are no comparative evaluations to date of different choices for the matrix polymer to which the antibodies are attached. Herein, multiple acrylic copolymers are studied as receptor layers with myelin basic protein and its corresponding antibody as an archetypal antibodyantigen pair. Stability against multiple washing steps and the capacity for immobilizing antibodies on polymers on device surfaces with the help of fluorescein isothiocyanate-labeled antibodies are compared. Electronic detection and selectivity are also observed. The conclusions provide guidance on the selection of bioreceptor material for increasing sensitivity and process stability of OFET biosensors.
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