Responsive Nanomaterials Research Articles

NIR light responsive MoS2 nanomaterials for rapid sterilization: Optimum photothermal effect via sulfur vacancy modulation

As the increasing problem of bacterial resistance has become the threaten to human health and environmental protection, the explorations of efficient and environmental-friendly antimicrobial agents are highly desired. Recently, vacancy engineering is regarded as the quite novel strategy to regulate the electronic structure of semiconductor Nanomaterials (NMs), largely improving their photocatalytic performance in rapid and safe sterilization. In this study, molybdenumsulfide(MoS2) NMs with different concentrations of sulfur vacancies (Vs) were synthesized through annealed at different temperature (i.e., 150 °C, 250 °C and 350 °C), providing the platform for studying the efficient bacterial inactivation of defective MoS2 NMs under the near-infrared light irradiation. The optimum photothermal conversion efficiency could be achieved with the appropriate concentration of Vs, through improving the light adsorption and preventing the recombination of photogenerated e−/h+ pairs. In addition, MoS2 NMs with the abundant Vs exhibited hyperthermia and strong binding ability to bacteria, leading to the severe damage to cell wall integrity, energy supply and antioxidant system. Collectively, these results focused on the relationship between optimum antibacterial efficiency and appropriate concentrations of Vs, providing new insights into the designation of photocatalysts with highly efficient sterilization.

Genistein-Derived ROS-Responsive Nanoparticles Relieve Colitis by Regulating Mucosal Homeostasis.

Disruption of intestinal homeostasis is an important event in the development of inflammatory bowel disease (IBD), and genistein (GEN) is a candidate medicine to prevent IBD. However, the clinical application of GEN is restricted owing to its low oral bioavailability. Herein, a reactive oxygen species (ROS)-responsive nanomaterial (defined as GEN-NP2) containing superoxidase dismutase-mimetic temporally conjugated β-cyclodextrin and 4-(hydroxymethyl)phenylboronic acid pinacol ester-modified GEN was prepared. GEN-NP2 effectively delivered GEN to the inflammation site and protected GEN from rapid metabolism and elimination in the gastrointestinal tract. In response to high ROS levels, GEN was site-specifically released and accumulated at inflammatory sites. Mechanistically, GEN-NP2 effectively increased the expression of estrogen receptor β (ERβ), simultaneously reduced the expression of proinflammatory mediators (apoptosis-associated speck-like protein containing a CARD (ASC) and Caspase1-p20), attenuated the infiltration of inflammatory cells, promoted autophagy of intestinal epithelial cells, inhibited the secretion of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), modulated the gut microbiota, and ultimately alleviated colitis. In addition, the oral administration of these nanoparticles showed excellent safety, thereby providing confidence in the further development of precise treatments for IBD.

NIR‐II Responsive Inorganic 2D Nanomaterials for Cancer Photothermal Therapy: Recent Advances and Future Challenges

AbstractNon‐invasive cancer photothermal therapy (PTT) is a promising replacement for traditional cancer treatments. The second near‐infrared region induced PTT (NIR‐II PTT, 1000–1500 nm) with less energy dissipation has been developed for deeper‐seated tumor treatment in recent years compared with the traditional first near‐infrared light (750–1000 nm). In addition, the use of emerging inorganic 2D nanomaterials as photothermal agents (PTAs) further enhanced PTT efficiency due to their intrinsic photothermal properties. NIR‐II light stimulated inorganic 2D nanomaterials for PTT is becoming a hot topic in both academic and clinical fields. This review summarizes the categories, structures, and photothermal conversion properties of inorganic 2D nanomaterials for the first time. The recent synergistic strategies of NIR‐II responsive PTT combined with other treatment approaches including chemotherapy, chemodynamic therapy, photodynamic therapy, radiotherapy are summarized. The future challenges and perspectives on these 2D nanomaterials for NIR‐II responsive PTT systems construction are further discussed.

A Soft On/Off Switch Based on the Electrochemically Reversible H-J Interconversion of a Porphyrin Membrane at an Electrified Liquid|Liquid Interface

Soft molecular assemblies that respond reversibly to external stimuli are attractive materials as on/off switches, in optoelectronic, memory and sensor technologies. In this presentation, the reversible structural rearrangement of a soft porphyrin membrane under an electrical potential stimulus in the absence of solid-state architectures will be presented.The free-floating porphyrin membrane lies at the interface between immiscible aqueous and organic electrolyte solutions and is formed through interfacial self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrins (ZnPor). A potential difference between the two immiscible electrolyte solutions induces the intercalation of bis(triphenylphosphoranylidene)ammonium cations from the organic electrolyte that exchange with protons in the porphyrin membrane. In situ UV/vis absorbance spectroscopy shows that this ionic intercalation and exchange induces a structural interconversion of the individual porphyrin molecules in the membrane from an H- to a J-type molecular configuration. These structural rearrangements are reversible over 30 potential cycles. In situ polarisation-modulation fluorescence spectroscopy further provides clear evidence of structural interconversion of the porphyrin membrane, as intercalation of the organic electrolyte cations significantly affects the latter’s emissive properties. By adjusting the pH of the aqueous phase, additional control of the electrochemically reversible structural interconversion can be achieved, with total suppression at pH 3.The work presented herein opens new opportunities to investigate the use of structurally dynamic soft supramolecular porphyrin assemblies at the interface between two immiscible electrolyte solution (ITIES) as switchable on/off responsive nanomaterials, with applications in optoelectronic, memory and sensor devices. Figure 1

RAFT synthesis of thioether-based, AB diblock copolymer nanocarriers for reactive oxygen species–triggered release

A well-defined AB diblock copolymer of 2-vinyl-4,4-dimethylazlactone (VDA) and N,N-dimethylacrylamide (DMA) was generated by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The VDA-DMA diblock copolymer was reacted with 2-(methylthio)ethylamine (MTEA) and 3-(methylthio)propylamine (MTPA) to yield two novel thioether functional diblock copolymers whose structure was confirmed using 1H NMR and FTIR spectroscopy. Both diblock copolymers formed micelles (20–30 nm) in aqueous media as confirmed by dynamic light scattering (DLS) and transmission electron microscopy. The self-assembled micelles were loaded with Nile Red, a model hydrophobic drug to study their ROS-triggered release mechanism. On addition of hydrogen peroxide (H2O2), the most common ROS species, the hydrophobic thioether core of these micelles oxidized, and both diblock copolymers became more hydrophilic. This triggered their disassembly and subsequent cargo release as characterized by UV–visible spectroscopy. The Nile Red loaded micelles demonstrated similar in-vitro ROS-mediated release when exposed to endogenous oxidants in a model inflammation environment simulated by the presence of activated macrophages. The responsive nanomaterials developed in this article have promising potential as drug carriers in applications where ROS-triggered delivery of cargo is required such as in inflammatory conditions.

Responsive Plasmonic Nanomaterials for Advanced Cancer Diagnostics.

Plasmonic nanostructures, particularly of noble-metal Au and Ag, have attracted long-lasting research interests because of their intriguing physical and chemical properties. Under light excitation, their conduction electrons can form collective oscillation with the electromagnetic fields at particular wavelength, leading to localized surface plasmon resonance (LSPR). The remarkable characteristic of LSPR is the absorption and scattering of light at the resonant wavelength and greatly enhanced electric fields in localized areas. In response to the chemical and physical changes, these optical properties of plasmonic nanostructures will exhibit drastic color changes and highly sensitive peak shifts, which has been extensively used for biological imaging and disease treatments. In this mini review, we aim to briefly summarize recent progress of preparing responsive plasmonic nanostructures for biodiagnostics, with specific focus on cancer imaging and treatment. We start with typical synthetic approaches to various plasmonic nanostructures and elucidate practical strategies and working mechanism in tuning their LSPR properties. Current achievements in using responsive plasmonic nanostructures for advanced cancer diagnostics will be further discussed. Concise perspectives on existing challenges in developing plasmonic platforms for clinic diagnostics is also provided at the end of this review.

Atomically precise nanoclusters with reversible isomeric transformation for rotary nanomotors

Thermal-stimuli responsive nanomaterials hold great promise in designing multifunctional intelligent devices for a wide range of applications. In this work, a reversible isomeric transformation in an atomically precise nanocluster is reported. We show that biicosahedral [Au13Ag12(PPh3)10Cl8]SbF6 nanoclusters composed of two icosahedral Au7Ag6 units by sharing one common Au vertex can produce two temperature-responsive conformational isomers with complete reversibility, which forms the basis of a rotary nanomotor driven by temperature. Differential scanning calorimetry analysis on the reversible isomeric transformation demonstrates that the Gibbs free energy is the driving force for the transformation. This work offers a strategy for rational design and development of atomically precise nanomaterials via ligand tailoring and alloy engineering for a reversible stimuli-response behavior required for intelligent devices. The two temperature-driven, mutually convertible isomers of the nanoclusters open up an avenue to employ ultra-small nanoclusters (1 nm) for the design of thermal sensors and intelligent catalysts.

Photo‐ and Magnetothermally Responsive Nanomaterials for Therapy, Controlled Drug Delivery and Imaging Applications

AbstractHyperthermia generates heat as a cure for illness and it is not a chemical treatment. Nanomaterials are supposed to provide novel mechanisms to tackle photothermal and magnetothermal problems, with the potential also to deal with specific approaches to care. The present review outlines recent developments in the field of photothermal and magnetothermal responsive nanomaterials and the photothermal approach mechanism over the last years. These photo/magnetothermal nanomaterials are classified into gold nanostructures (various shapes), carbon nanomaterials (CNTs, fullerene, carbon quantum dots, and graphene), inorganic nanomaterials (Fe, Pt, Pd, Bi, MOF, MoSe2, inorganic quantum dots, etc.) and organic nanoparticles (PLGA (Poly Lactic‐co‐Glycolic Acid) and other nanopolymers). Different groups may be placed together to improve the potential of the photothermal/magnetothermal effects, treatments, drug delivery, and imaging. The review also describes synthesis strategies for photothermal/magnetothermal nanomaterials, physicochemical characterization, the role of size, size distribution, shape, and surface coating of nanomaterials, challenges, and future scopes of photothermal/magnetothermal responsive nanomaterials for therapy, controlled drug delivery, and imaging applications. The recent development in nanomaterial has shown great potential for tumor diagnostic and therapeutic applications in hyperthermia. Magnetic hyperthermia (also called thermal therapy or thermotherapy) is a type of cancer treatment in which body tissue is exposed to high temperatures (up to 41 °C) in presence of a magnetic field. Research has shown that high temperatures can damage and kill cancer cells, usually with minimal injury to normal tissues. By killing cancer cells and damaging proteins and structures within cells, hyperthermia can necrotize tumor cells. This treatment can be local, regional, or whole‐body hyperthermia, depending on the extent of the area being treated. Hyperthermia can be combined with anticancer drugs or chemotherapy to enhance cancer treatment. In this article, we have discussed recent nanomaterials utilized for this treatment, mechanism, and synthesis methods.

Polydopamine-Mesoporous Silica Core-Shell Nanoparticles for Combined Photothermal Immunotherapy.

Cancer immunotherapy involves a cascade of events that ultimately leads to cytotoxic immune cells effectively identifying and destroying cancer cells. Responsive nanomaterials, which enable spatiotemporal orchestration of various immunological events for mounting a highly potent and long-lasting antitumor immune response, are an attractive platform to overcome challenges associated with existing cancer immunotherapies. Here, we report a multifunctional near-infrared (NIR)-responsive core-shell nanoparticle, which enables (i) photothermal ablation of cancer cells for generating tumor-associated antigen (TAA) and (ii) triggered release of an immunomodulatory drug (gardiquimod) for starting a series of immunological events. The core of these nanostructures is composed of a polydopamine nanoparticle, which serves as a photothermal agent, and the shell is made of mesoporous silica, which serves as a drug carrier. We employed a phase-change material as a gatekeeper to achieve concurrent release of both TAA and adjuvant, thus efficiently activating the antigen-presenting cells. Photothermal immunotherapy enabled by these nanostructures resulted in regression of primary tumor and significantly improved inhibition of secondary tumor in a mouse melanoma model. These biocompatible, biodegradable, and NIR-responsive core-shell nanostructures simultaneously deliver payload and cause photothermal ablation of the cancer cells. Our results demonstrate potential of responsive nanomaterials in generating highly synergistic photothermal immunotherapeutic response.

Multifunctional Smart Yolk-Shell Nanostructure with Mesoporous MnO2 Shell for Enhanced Cancer Therapy.

Manganese dioxide (MnO2) nanostructures have aroused great interest among analytical and biological medicine researchers as a unique type of tumor microenvironment (TME)-responsive nanomaterial. However, reliable approaches for synthesizing yolk-shell nanostructures (YSNs) with mesoporous MnO2 shell still remain exciting challenges. Herein, a YSN (size, ∼75 nm) containing a mesoporous MnO2 shell and Er3+-doped upconversion/downconversion nanoparticle (UCNP) core with a large cavity is demonstrated for the first time. This nanostructure not only integrates diverse functional components including MnO2, UCNPs, and YSNs into one system but also endows a size-controllable hollow cavity and thickness-tunable MnO2 layers, which can load various guest molecules like photosensitizers, methylene blue (MB), and the anticancer drugs doxorubicin (DOX). NIR-II fluorescence and photoacoustic (PA) imaging from UCNP and MB, respectively, can monitor the enrichment of the nanomaterials in the tumors for guiding chemo-photodynamic therapy (PDT) in vivo. In the TME, degradation of the mMnO2 shell by H2O2 and GSH not only generates Mn2+ for tumor-specific T1-MR imaging but also releases O2 and drugs for tumor-specific treatment. The result confirmed that imaging-guided enhanced chemo-PDT combination therapy that benefited from the unique structural features of YSNs could substantially improve the therapeutic effectiveness toward malignant tumors compared to monotherapy.

Radio Frequency Driven Heating of Catalytic Reactors for Portable Green Chemistry

AbstractHere, a novel integration is proposed for radio frequency (1–300 MHz) responsive nanomaterials with conventional catalytic materials to realize a new class of heterogeneous catalysts that undergo uniform volumetric and localized heating to drive chemical transformations at the modular scale. Approximately 80% of chemical manufacturing involves heterogeneous catalytic reactions, which currently require heating via steam utilities or fired furnaces, and thus contribute to global greenhouse gas emissions while also limiting distributed chemicals production. This approach uses an electric route to produce chemicals where radio frequency (RF) electromagnetic fields and their interaction with carbon/ceramic nanomaterials are utilized to selectively heat the catalyst composition. A proof‐of‐concept is demonstrated using the commonly studied methanol steam reforming reaction on a platinum catalyst. In this study, two RF susceptors are used: carbon nanotubes and silicon carbide fibers. The conversion rate of methanol using RF heating is comparable to oven heating at varying temperature and catalyst combinations. This is a potential improvement over conventional catalytic reactors in that it enables small, safe, sustainable, on‐site, and on‐demand production of chemicals in the absence of traditional manufacturing infrastructure.

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.

Efficient degradation of nonylphenol and 2,4-dinitrophenol by sunlight responsive hexacyanocobaltates nanostructures

Nonylphenol (NP) and 2,4-dinitrophenol (2,4-DNP) are causing serious environmental concerns owing to their toxic, carcinogenic, persistentancy and bio-accumulating properties. It has been found that their concentrations are abundant near to industries and in many water bodies due to untreated release. Therefore, their complete removals using low-cost, efficient and environmental friendly techniques from water are required. Sunlight active metal hexacyanocobaltates nanoparticles have been reported beneficial heterogeneous and recoverable catalysts. Therefore, a green route based on utilization of natural material (Azadirachta indica leaf extract) and water was developed for the synthesis of cadmium hexacynocobaltate (CdHCC) and manganese hexacyanocobaltate (MnHCC) nanoparticles. Electron microscopic analysis revealed nanometer range (∼100 nm) for CdHCC and MnHCC particles. Synthesized nanomaterials were employed for the degradation of substituted phenols under direct Sunlight to follow the natural scenario. Maximum degradation of selected phenols (CdHCC- NP: 70 %; 2,4-DNP: 77 %, MnHCC- NP: 90 %; 2,4-DNP: 97 %) required 25 mg of catalyst per 50 mg L−1 of phenols at neutral pH under Sunlight irradiation. This excellent photocatalytic activity of the MnHCC might be due to high surface activity (surface areas of CdHCC and MnHCC were 95 m2 g-1 and 448 m2 g-1, respectively) and particles stability (as observed from zeta potential, CdHCF: -13.5 mV; MnHCF: -19.2 mV). The degradations followed first-order kinetics. Adsorption plots were best fitted with Langmuir isotherm. GC–MS analysis of the final reaction mixtures showed the formation of low molecular weight and safer compounds, which were finally mineralized. Degradation mechanism of NP and 2,4-DNP involved OH radicals based oxidation, hydroxylation, and ring-opening. These materials were found reusable up to ten times revealing sustainability. Overall, these Sunlight responsive novel metal hexacyanocobaltate nanomaterials might be promising and sustainable materials for remediation of environmental contaminants.

Photothermal/sonodynamic therapy of melanoma tumor by a gold/manganese dioxide nanocomposite: In vitro and in vivo studies.

Nanosized materials have favorable applications in nanomedicine including photothermal therapy (PTT) and sonodynamic therapy (SDT) of most malignancies. Since conventional methods of cancer treatment encounter limitations, development of other efficient routes is quite necessary. In this study, a gold/manganese dioxide nanocomposite (Au/MnO2 NC) was synthesized as a novel photo- and sono- responsive nanomaterial that was activated upon laser light of 808-nm wavelength irradiation or ultrasound exposure for cancer treatment applications. The synthesized nanocomposite comprised gold nanoparticles of about 125 ± 66 nm in diameter adhered to manganese dioxide nanoroads of 77 ± 30 nm in diameter and up to 2 μm length. Au/MnO2 NC represented a very good photothermal and sonodynamic conversion ability. Cytotoxicity of Au/MnO2 NC toward the C540 (B16/F10) cell line was evaluated through thermal ablation and reactive oxygen species (ROS) generation upon phototherapy and sonotherapy, respectively. Intratumoral injection of a low-dose of Au/MnO2 NC into a melanoma tumor-bearing animal model followed by laser and ultrasound radiation led to necrosis in the tumor tissue. The findings revealed that Au/MnO2 NC is aphotosensitizer/sonosensitizer for PTT and SDT of cancer.

Self-Assembled Multiple-Enzyme Composites for Enhanced Synergistic Cancer Starving-Catalytic Therapy.

Inspired by the particularity of tumor microenvironments, including acidity and sensibility to reactive oxygen species (ROS), advanced and smart responsive nanomaterials have recently been developed. The present study synthesized tumor-targeted and pH-sensitive supramolecular micelles that self-assembled via host-guest recognition. The micelles consumed intratumoral glucose and lactate via loading with glucose oxidase (GOD) and lactate oxidase (LOD). Intratumoral glucose and lactate were converted into hydrogen peroxide (H2O2) and were sequentially reduced to highly toxic hydroxyl radicals (•OH) via the peroxidase (POD)-like activity of the loaded C-dot nanozymes. Tumor-killing effects were observed via cascade catalytic reactions. After an intravenous injection, the nanocomposite exhibited an excellent tumor-targeted ability with good biocompatibility, which demonstrated its effective antitumor effect. The nanocomposite effectively combined starvation and catalytic therapies and exerted a synergistic anticancer effect with minimal side effects and without external addition.

Polymorphic Self-Organization of Lauroyl Peptide in Response to pH and Concentration.

Amphipathic peptides are attractive building blocks for the preparation of self-assembling, bio-inspired, and stimuli responsive nanomaterials with pharmaceutical interest. The bioavailability of these materials can be improved with the insertion of d amino acid residues to avoid fast proteolysis in vivo. With this knowledge, a new lauroyl peptide consisting of a sequence of glycine, glycine, d-serine, and d-lysine was designed. In spite of its simple sequence, this lipopeptide self-assembles into spherical micelles at acid pH, when the peptide moiety adopts disordered conformations. Self-aggregates reshape toward fibers at basic pH, following the conformational transition of the peptide region from random coil to β-sheet. Finally, hydrogels are achieved at basic pH and higher concentrations. The transition from random coil to β-sheet conformation of the peptide headgroup obtained by increasing pH was monitored by circular dichroism and vibrational spectroscopy. A structural analysis, performed by combining dynamic light scattering, small-angle X-ray scattering, transmission electron microscopy, and molecular dynamic simulations, demonstrated that the transition allows the self-assemblies to remodel from spherical micelles to rodlike shapes, to long fibers with rectangular cross-section and a head-tail-tail-head structure. The viscoelastic behavior of the hydrogels formed at the highest pH was investigated by rheology measurements.

DNA binding and NIR triggered DNA release from quaternary ammonium modified poly(allylamine hydrochloride) functionalized and folic acid conjugated reduced graphene oxide nanocomposites

Reduced graphene oxide (RGO) has shown tremendous potential as a NIR responsive nanomaterial and has been extensively explored for NIR mediated photothermal therapy and drug delivery. However, the potential of NIR as a stimulus to trigger release of entrapped/complexed DNA from its surface have not been explored. Strong complexation between the loaded cargo and the carrier often leads to no-release or decrease in the release of the therapeutic cargo. Herein, we investigated NIR as a stimulus for inducing DNA release from RGO nanocomposites. A quaternary ammonium modified poly(allylamine hydrochloride) functionalized RGO nanocomposite (RGO-MPAH) was synthesized, which was further tagged with a targeting moiety, folic acid (FA). The structural, optical and chemical properties of the synthesized nanocomposites were characterized which validated successful reduction and functionalization of GO with PAH/MPAH. The nanocomposites were found to be non-toxic and showed excellent DNA binding ability at complexation ratios as low as 3:1 (w/w). Additionally, the nanocomposites demonstrated NIR responsive release of complexed DNA from their surfaces, with RGO-PAH showing maximum DNA release followed by RGO-MPAH and RGO-MPAH-FA. This study shows the potential of NIR light to act as a stimulus for inducing release of entrapped nucleic acids from the surface of nanocarriers.

Construction of immobilized 0D/1D heterostructure photocatalyst Au/CuS/CdS/TiO2 NBs with enhanced photocatalytic activity towards moxifloxacin degradation

Strong absorption in a wide wavelength range and effective charge separation are main factors for improving photocatalytic activity of semiconductor photocatalysts. Herein, immobilized zero-dimensional/one-dimensional (0D/1D) Au/CuS/CdS/TiO2 nanobelts (Au/CuS/CdS/TiO2 NBs) heterostructure photocatalyst with innovative morphology and appropriate band-gap configuration was synthesized for the first time. For this construction, TiO2 NBs provide the 1D structure for a large superficial area and fast electron mobility, 0D CdS and CuS nanoparticles are the visible-light responsive nanomaterials, and Au nanoparticles serve as the surface plasmon resonance effect and electron transfer. The Au/CuS/CdS/TiO2 NBs showed improved photocatalytic performance towards moxifloxacin (MOX) degradation, which can be attributed to the promoted photoabsorption contribution and enhanced separation and transfer of photoexcited electrons and holes. The morphology, constitution, optical and electrochemical properties of the prepared photocatalyst were investigated comprehensively. Moreover, the photocatalytic degradation mechanism and degradation by-products of moxifloxacin were studied. Results showed that the OH, O2− and h+ are the main chemical oxidation species responsible for the degradation of MOX. Eight different photocatalytic degradation products were detected. The stability assessment showed that photodissolution plays the primary role in the photocatalytic performance decrease of Au/CuS/CdS/TiO2 NBs. This work gives a promising strategy to rational design efficient hybrid metal-semiconductor photocatalysts for solar energy conversion.

Reversibly pH-responsive gold nanoparticles and their applications for photothermal cancer therapy

Microenvironment responsive nanomaterials are attractive for therapeutic applications with regional specificity. Here we report pH responsive gold nanoparticles which are designed to aggregate in acidic condition similar to cancer environment and returned to its original disassembled states in a physiological pH. The pH responsive behavior of the particles is derived by change of electrostatic interaction among the particles where attraction and repulsion play a major role in low and high pH of the environment, respectively. Since different electrostatic interaction behavior of the particles in varied pH is induced not by irreversible chemical change but by simple protonation differences, the pH responsive process of assembly and disassembly is totally reversible. The low pH specific aggregation of gold nanoparticles resulted in red shift of plasmonic absorption peak and showed higher photothermal efficacy in acidic pH than in normal physiological pH. The low pH specific photothermal effect with long wave laser irradiation was directly applied to cancer specific photothermal therapy and resulted higher therapeutic effect for melanoma cancer cells than non-pH responsive gold nanoparticles.

QCM-D assay for quantifying the swelling, biodegradation, and protein adsorption of intelligent nanogels.

Environmentally responsive nanomaterials have been developed for drug delivery applications, in an effort to target and accumulate therapeutic agents at sites of disease. Within a biological system, these nanomaterials will experience diverse conditions which encompass a variety of solute identities and concentrations. In this study, we developed a new quartz crystal microbalance with dissipation (QCM-D) assay, which enabled the quantitative analysis of nanogel swelling, protein adsorption, and biodegradation in a single experiment. As a proof of concept, we employed this assay to characterize non-degradable and biodegradable poly(acrylamide-co-methacrylic acid) nanogels. We compared the QCM-D results to those obtained by dynamic light scattering to highlight the advantages and limitations of each method. We detailed our protocol development and practical recommendations, and hope that this study will serve as a guide for others to design application-specific QCM-D assays within the nanomedicine domain.