Stimuli-Responsive Aptamer-Drug Conjugates for Targeted Drug Delivery and Controlled Drug Release.

Chemotherapy is widely used for cancer therapy but with unsatisfied efficacy, mainly due to the inefficient delivery of anticancer agents. Among the critical "five steps" drug delivery process, internalization into tumor cells and intracellular drug release are two important steps for the overall therapeutic efficiency. Strategy based on active targeting or TME-responsive is developed individually to improve therapeutic efficiency, but with limited improvement. However, the combination of these two strategies could potentially augment the drug delivery efficiency and therapeutic efficiency, consequently. Therefore, this work constructs a library of stimuli-responsive aptamer-drug conjugates (srApDCs), as "dual-targeted" strategy for cancer treatment that enables targeted drug delivery and controlled drug release. Specifically, this work uses different stimuli-responsive linkers to conjugate a tumor-targeting aptamer (i.e., AS1411) with drugs, forming the library of srApDCs for targeted cancer treatment. This design hypothesis is validated by the experimental data, which indicated that the aptamer could selectively enhance uptake of the srApDCs and the linkers could be cleaved by pathological cues in the TME to release the drug payload, leading to a significant enhancement of therapeutic efficacy. These results underscore the potential of the approach, providing a promising methodology for cancer therapy.

Combination Therapy of Lox Inhibitor and Stimuli-Responsive Drug for Mechanochemically Synergistic Breast Cancer Treatment.

Chemotherapy based on small molecule drugs, hormones, cycline kinase inhibitors, and monoclonal antibodies has been widely used for breast cancer treatment in the clinic but with limited efficacy, due to the poor specificity and tumor microenvironment (TME)-caused diffusion barrier. Although monotherapies targeting biochemical cues or physical cues in the TME have been developed, none of them can cope with the complex TME, while mechanochemical combination therapy remains largely to be explored. Herein, a combination therapy strategy based on an extracellular matrix (ECM) modulator and TME-responsive drug for the first attempt of mechanochemically synergistic treatment of breast cancer is developed. Specifically, based on overexpressed NAD(P)H quinone oxidoreductase 1 (NQO1) in breast cancer, a TME-responsive drug (NQO1-SN38) is designed and it is combined with the inhibitor (i.e., ß-Aminopropionitrile, BAPN) for Lysyl oxidases (Lox) that contributes to the tumor stiffness, for mechanochemical therapy. It is demonstrated that NQO1 can trigger the degradation of NQO1-SN38 and release SN38, showing nearly twice tumor inhibition efficiency compared with SN38 treatment in vitro. Lox inhibition with BAPN significantly reduces collagen deposition and enhances drug penetration in tumor heterospheroids in vitro. It is further demonstrated that the mechanochemical therapy showed outstanding therapeutic efficacy in vivo, providing a promising approach for breast cancer therapy.

Extracellular matrix physical properties govern the diffusion of nanoparticles in tumor microenvironment.

Nanoparticles (NPs) are confronted with limited and disappointing delivery efficiency in tumors clinically. The tumor extracellular matrix (ECM), whose physical traits have recently been recognized as new hallmarks of cancer, forms a main steric obstacle for NP diffusion, yet the role of tumor ECM physical traits in NP diffusion remains largely unexplored. Here, we characterized the physical properties of clinical gastric tumor samples and observed limited distribution of NPs in decellularized tumor tissues. We also performed molecular dynamics simulations and in vitro hydrogel experiments through single-particle tracking to investigate the diffusion mechanism of NPs and understand the influence of tumor ECM physical properties on NP diffusion both individually and collectively. Furthermore, we developed an estimation matrix model with evaluation scores of NP diffusion efficiency through comprehensive analyses of the data. Thus, beyond finding that loose and soft ECM with aligned structure contribute to efficient diffusion, we now have a systemic model to predict NP diffusion efficiency based on ECM physical traits and provide critical guidance for personalized tumor diagnosis and treatment.

The effects of serum albumin pre-adsorption of nanoparticles on protein corona and membrane interaction: A molecular simulation study.

As a platform to deliver imaging and therapeutic agents to targeted sites in vivo, nanoparticles (NPs) have widespread applications in diagnosis and treatment of cancer. However, the poor in vivo delivery efficiency of nanoparticles limits its potential for further application. Once enter the physiological environment, nanoparticles immediately interact with proteins and form protein corona, which changes the physicochemical properties of nanoparticle surface and further affects their transport. In this study, we performed molecular dynamics simulations to study the adsorption mechanism of nanoparticles with various surface modifications and different proteins (e.g., human serum albumin, complement protein C3b), and their interactions with cell membrane. The results show that protein human serum albumin prefers to interact with hydrophobic and positively charged nanoparticles, while the protein C3b prefers the hydrophobic and charged nanoparticles. The pre-adsorption of human serum albumin on the nanoparticle surface obviously decreases the interaction of nanoparticle with C3b. Furthermore, the high amount of protein pre-adsorption could decrease the probability of nanoparticle-membrane interaction. These results indicate that appropriate modification of nanoparticles with protein provides nanoparticles with better capability of targeting, which could be used to guide nanoparticle design and improve transport efficiency.

Biomolecular Pathways of Cryoinjuries in Low-Temperature Storage for Mammalian Specimens.

Low-temperature preservation could effectively extend in vitro storage of biological materials due to delayed or suspended cellular metabolism and decaying as illustrated by the Arrhenius model. It is widely used as an enabling technology for a variety of biomedical applications such as cell therapeutics, assisted reproductive technologies, organ transplantation, and mRNA medicine. Although the technology to minimize cryoinjuries of mammalian specimens during preservation has been advanced substantially over past decades, mammalian specimens still suffer cryoinjuries under low-temperature conditions. Particularly, the molecular mechanisms underlying cryoinjuries are still evasive, hindering further improvement and development of preservation technologies. In this paper, we systematically recapitulate the molecular cascades of cellular injuries induced by cryopreservation, including apoptosis, necroptosis, ischemia-reperfusion injury (IRI). Therefore, this study not only summarizes the impact of low-temperature preservations on preserved cells and organs on the molecular level, but also provides a molecular basis to reduce cryoinjuries for future exploration of biopreservation methods, materials, and devices.

Quantifying and Adjusting Plasmon-Driven Nano-Localized Temperature Field around Gold Nanorods for Nucleic Acids Amplification.

Fast nucleic acid (NA) amplification has found widespread biomedical applications, where high thermocycling rate is the key. The plasmon-driven nano-localized thermocycling around the gold nanorods (AuNRs) is a promising alternative, as the significantly reduced reaction volume enables a rapid temperature response. However, quantifying and adjusting the nano-localized temperature field remains challenging for now. Herein, a simple method is developed to quantify and adjust the nano-localized temperature field around AuNRs by combining experimental measurement and numerical simulation. An indirect method to measure the surface temperature of AuNRs is first developed by utilizing the temperature-dependent stability of Authiol bond. Meanwhile, the relationship of AuNRs' surface temperature with the AuNRs concentration and laser intensity, is also studied. In combination with thermal diffusion simulation, the nano-localized temperature field under the laser irradiation is obtained. The results show that the restricted reaction volume (≈aL level) enables ultrafast thermocycling rate (>104  °C s-1 ). At last, a duplex-specific nuclease (DSN)-mediated isothermal amplification is successfully demonstrated within the nano-localized temperature field. It is envisioned that the developed method for quantifying and adjusting the nano-localized temperature field around AuNRs is adaptive for various noble metal nanostructures and will facilitate the development of the biochemical reaction in the nano-localized environment.

Evaporation-Induced Diffusion Acceleration in Liquid-Filled Porous Materials.

Liquid-filled porous materials exist widely in nature and engineering fields, with the diffusion of substances in them playing an important role in system functions. Although surface evaporation is often inevitable in practical scenarios, the evaporation effects on diffusion behavior in liquid-filled porous materials have not been well explored yet. In this work, we performed noninvasive diffusion imaging experiments to observe the diffusion process of erioglaucine disodium salt dye in a liquid-filled nitrocellulose membrane under a wide range of relative humidities (RHs). We found that evaporation can significantly accelerate the diffusion rate and alter concentration distribution compared with the case without evaporation. We explained the accelerated diffusion phenomenon by the mechanism that evaporation would induce a weak flow in liquid-filled porous materials, which leads to convective diffusion, i.e., evaporation-induced flow and diffusion (EIFD). Based on the EIFD mechanism, we proposed a convective diffusion model to quantitatively predict the diffusion process in liquid-filled porous materials under evaporation and experimentally validated the model. Introducing the dimensionless Peclet (P e) number to measure the relative contribution of the evaporation effect to pure molecular diffusion, we demonstrated that even at a high RH of 95%, where the evaporation effect is usually assumed negligible in common sense, the evaporation-induced diffusion still overwhelms the molecular diffusion. The flow velocity induced by evaporation in liquid-filled porous materials was found to be 0.4-5 µm/s, comparable to flow in many biological and biomedical systems. The present analysis may help to explain the driving mechanism of tissue perfusion and provide quantitative analysis or inspire new control methods of flow and material exchange in numerous cutting-edge technologies, such as paper-based diagnostics, hydrogel-based flexible electronics, evaporation-induced electricity generation, and seawater purification.

Tailoring patchy nanoparticle design to modulate serum albumin adsorption and membrane interaction.

When nanoparticles (NPs) enter into the biological system, a wide range of proteins will coat on their surfaces forming protein corona, which changes the initial synthetic characteristics of NPs to the biological identity, resulting in the loss of their targets or specially designed properties. Although pre-coating with proteins would reduce the protein corona formation, they may diminish the targeting moieties in the transport process. Patchy NPs can offer unique advantages of asymmetry, heterogeneity, and multi-functions. This has inspired us to use the asymmetry to realize the versatility of NPs, to accommodate stealth and targeting functions. In this study, we performed molecular dynamics simulations to investigate the adsorption mechanism between patchy NPs and human serum albumin, and the interaction mechanism between NP-HSA and the membrane. The results show that there is a high probability for HSA to interact with the hydrophobic, or charged brushes of patchy NPs. The adsorption sites, as calculated through the contact probability between NPs and the residues, depend on the NP surface properties. Furthermore, the HSA adsorption on NPs could improve the NP-membrane interaction. The simulation results provide deep understanding of the NP interaction mechanism, which would help the NP design for their biomedical applications.

Engineering extracellular matrix to improve drug delivery for cancer therapy.

As an effective platform to deliver therapeutic drugs into tumors, nanoparticles (NPs) have shown great potential for cancer therapy. However, the tumor microenvironment (TME) contains diverse barriers to the transport of NPs, particularly the dense extracellular matrix (ECM). Thus, engineering the tumor ECM is a promising way to improve drug delivery by degrading existing ECM and/or blocking ECM synthesis. In this review, we present the state-of-the-art advances in engineering the tumor ECM to improve the therapeutic efficacy of NPs, and highlight their advantages and limitations.

A two-dimensional mathematical model for analyzing the effects of capture probe properties on the performance of lateral flow assays.

Lateral flow assays (LFAs) are promising candidates in biomedical diagnosis fields due to their rapid, low-cost, and portable features. However, improving their sensitivity remains challenging due to the unclear roles of capture probes with different distribution formats on the particle transfer and capturing in the test line. Therefore, we designed experiments and observed an asymmetrical U-shaped distribution of control probes throughout the NC membrane thickness. Based on this outcome, a two-dimensional mathematical model based on the Langmuir surface reaction kinetics was developed to investigate the effect of capture probe distributions on LFA performance. A two-dimensional model was qualitatively validated by comparing with the experimental results and the simulations of the reported one-dimensional model. Then, a higher detection signal was achieved by using the U-shaped distribution of capture probes throughout the NC membrane thickness instead of a uniform distribution. Furthermore, when the NC membrane thickness was less than 110 µm, the ratio of the detection signal in the visible region to the signal in the total section at the test line was above 13%. A thin NC membrane will produce a strong detection signal in the visible region at the test line. The developed model is capable of providing direct predictions in designing highly sensitive LFAs.

Sensitivity Enhancement of Nucleic Acid Lateral Flow Assays through a Physical-Chemical Coupling Method: Dissoluble Saline Barriers.

Nucleic acid lateral flow assays (NALFAs) have attracted much attention due to their rapid, robust, simple, and cost-effective features. However, the current NALFAs are still limited by low sensitivity because of the poor understanding and control of the underlying complex flow and reaction processes. Although enormous efforts have been devoted to enhancing detection sensitivity of NALFAs, developing simple NALFAs with high sensitivity remains difficult. Thus, we proposed a novel physical-chemical coupling method using dissoluble saline barriers and developed the corresponding mathematical model to better understand the underlying processes to enhance the NALFA sensitivity. Through optimizing the design parameters (e.g., saline barriers patterns, volume, and concentrations) experimentally and numerically, we achieved the highest 10-fold sensitivity enhancement for detection of nucleic acids (including HBV, Staphylococcus aureus, and salmonella as model targets) using this method. The physical-chemical coupling method offers a facile strategy for developing highly sensitive NALFAs.

An improved detection limit and working range of lateral flow assays based on a mathematical model.

Lateral flow assays (LFAs) have attracted considerable attention in biomedical diagnostics. However, it's still challenging to achieve a high detection sensitivity and extensive working range, mainly because the underlying mechanism of complex reaction processes in LFAs remains unclear. Many mathematical models have been developed to analyze the complex reaction processes, which are only qualitative with limited guidance for LFA design. Now, a semi-quantitative convection-diffusion-reaction model is developed by considering the kinetics of renaturation of nucleic acids and the model is validated by our experiments. We established a method to convert the LFA design parameters between the simulation and experiment (i.e., inlet reporter particle concentration, initial capture probe concentration, and association rate constant), with which we achieved a semi-quantitative comparison of the detection limit and working range between simulations and experiments. Based on our model, we have improved the detection sensitivity and working range by using high concentrations of the inlet reporter particles and initial capture probe. Besides, we also found that target nucleic acid sequences with a high association rate constant are beneficial to improve the LFA performance. The developed model can predict the detection limit and working range and would be helpful to optimize the design of LFAs.

Parametric Study on Electric Field-Induced Micro-/Nanopatterns in Thin Polymer Films.

Electric field-induced micro-/nanopatterns in thin polymer films, sometimes referred as electrohydrodynamic patterning, is a promising technique to fabricate micro-/nanostructures. Extensive attention has been attracted because of its advantages in microcontact (easy demolding) and low cost. Although considerable work has been done on this technique, including both experimental and theoretical ones, there still appears a requirement for understanding the mechanism of electrohydrodynamic patterning. Thus, we systematically studied the effect of different parameters on electrohydrodynamic patterning with a numerical phase field model. Previous researchers usually employed lubrication approximation (i.e., long-wave approximation) to simplify the numerical model. However, this approximation would lose its validity if the structure height is on the same scale or larger than the wavelength, which occurs in most cases. Thus, we abandoned the lubrication approximation and solved the full governing equations for fluid flow and electric field. In this model, the deformation of polymer film is described by the phase field model. As to the electric field, the leaky dielectric model is adopted in which both electrical permittivity and conductivity are considered. The fluid flow together with electric field is coupled together in the framework of phase field. By this model, the effect of physical parameters, such as external voltage, template structure height, and polymer conductivity, is studied in detail. After that, the governing equations are nondimesionalized to analyze the relationship between different parameters. A dimensionless parameter, electrical Reynolds number ER, is defined, for which, a large value would simplify the electric field to perfect dielectric model and a small value leads it to steady leaky model. These findings and results may enhance our understanding of electrohydrodynamic patterning and may be a meaningful guide for experiments.

Clinching for sheet materials.

Latest developments in the clinching of sheet materials are reviewed in this article. Important issues are discussed, such as tool design, process parameters and joinability of some new lightweight sheet materials. Hybrid and modified clinching processes are introduced to a general reader. Several unaddressed issues in the clinching of sheet materials are identified.

Coarse-grained molecular dynamics studies of the translocation mechanism of polyarginines across asymmetric membrane under tension.

Understanding interactions between cell-penetrating peptides and biomembrane under tension can help improve drug delivery and elucidate mechanisms underlying fundamental cellular events. As far as the effect of membrane tension on translocation, it is generally thought that tension should disorder the membrane structure and weaken its strength, thereby facilitating penetration. However, our coarse-grained molecular dynamics simulation results showed that membrane tension can restrain polyarginine translocation across the asymmetric membrane and that this effect increases with increasing membrane tension. We also analyzed the structural properties and lipid topology of the tensed membrane to explain the phenomena. Simulation results provide important molecular information on the potential translocation mechanism of peptides across the asymmetric membrane under tension as well as new insights in drug and gene delivery.

Molecular analysis of interactions between a PAMAM dendrimer-paclitaxel conjugate and a biomembrane.

Understanding the underlying mechanism of nanomedicine-biomembrane interactions is important for the design and optimization of payload delivery systems. This study investigates the interactions between polyamidoamine (PAMAM) dendrimer-paclitaxel conjugates and biomembranes using coarse-grained molecular dynamics simulations. We found that acidic conditions (e.g., pH ∼ 5) and membrane asymmetry can improve the conjugate penetration. Paclitaxel (PTX) distributions on a G4 PAMAM dendrimer can affect interactions via the penetration mechanism, although they have no significant effect on interactions via the adsorption mechanism. The random distribution of PTX can enhance the ability of PTX molecules to pass through asymmetric membranes. Furthermore, the penetration process becomes more difficult with increasing paclitaxel loading ratios. These results provide molecular insights into the precise translocation mechanism of dendrimer-drug conjugates and thus provide suggestions for drug design and delivery.

Molecular analysis of interactions between dendrimers and asymmetric membranes at different transport stages.

Studying dendrimer-biomembrane interactions is important for understanding drug and gene delivery. In this study, coarse-grained molecular dynamics simulations were performed to investigate the behaviors of polyamidoamine (PAMAM) dendrimers (G4 and G5) as they interacted with asymmetric membranes from different sides of the bilayer, thus mimicking different dendrimer transport stages. The G4 dendrimer could insert into the membrane during an equilibrated state, and the G5 dendrimer could induce pore formation in the membrane when the dendrimers interacted with the outer side (outer interactions) of an asymmetric membrane [with 10% dipalmitoyl phosphatidylserine (DPPS) in the inner leaflet of the membrane]. During the interaction with the inner side of the asymmetric membrane (inner interactions), the G4 and G5 dendrimers only adsorbed onto the membrane. As the membrane asymmetry increased (e.g., increased DPPS percentage in the inner leaflet of the membrane), the G4 and G5 dendrimers penetrated deeper into the membrane during the outer interactions and the G4 and G5 dendrimers were adsorbed more tightly onto the membrane for the inner interactions. When the DPPS content reached 50%, the G4 dendrimer could completely penetrate through the membrane from the outer side to the inner side. Our study provides molecular understanding and reference information about different dendrimer transport stages during drug and gene delivery.