NIR-triggered release of caged nitric oxide using upconverting nanostructured materials

Macrophage-mediated delivery of light activated nitric oxide prodrugs with spatial, temporal and concentration control

Nitric oxide (NO) holds great promise as a treatment for cancer hypoxia, if its concentration and localization can be precisely controlled. Here, we report a "Trojan Horse" strategy to provide the necessary spatial, temporal, and dosage control of such drug-delivery therapies at targeted tissues. Described is a unique package consisting of (1) a manganese-nitrosyl complex, which is a photoactivated NO-releasing moiety (photoNORM), plus Nd3+-doped upconverting nanoparticles (Nd-UCNPs) incorporated into (2) biodegradable polymer microparticles that are taken up by (3) bone-marrow derived murine macrophages. Both the photoNORM [Mn(NO)dpaqNO2 ]BPh4(dpaqNO2 = 2-[N,N-bis(pyridin-2-yl-methyl)]-amino-N'-5-nitro-quinolin-8-yl-acetamido) and the Nd-UCNPs are activated by tissue-penetrating near-infrared (NIR) light at ∼800 nm. Thus, simultaneous therapeutic NO delivery and photoluminescence (PL) imaging can be achieved with a NIR diode laser source. The loaded microparticles are non-toxic to their macrophage hosts in the absence of light. The microparticle-carrying macrophages deeply penetrate into NIH-3T3/4T1 tumor spheroid models, and when the infiltrated spheroids are irradiated with NIR light, NO is released in quantifiable amounts while emission from the Nd-UCNPs provides images of microparticle location. Furthermore, varying the intensity of the NIR excitation allows photochemical control over NO release. Low doses reduce levels of hypoxia inducible factor 1 alpha (HIF-1α) in the tumor cells, while high doses are cytotoxic. The use of macrophages to carry microparticles with a NIR photo-activated theranostic payload into a tumor overcomes challenges often faced with therapeutic administration of NO and offers the potential of multiple treatment strategies with a single system.

Use of gasotransmitters for the controlled release of polymer-based nitric oxide carriers in medical applications

Nitric Oxide (NO) is a small molecule gasotransmitter synthesized by nitric oxide synthase in almost all types of mammalian cells. NO is synthesized by NO synthase by conversion of l-arginine to l-citrulline in the human body. NO then stimulates soluble guanylate cyclase, from which various physiological functions are mediated in a concentration-dependent manner. High concentrations of NO induce apoptosis or antibacterial responses whereas low NO circulation leads to angiogenesis. The bidirectional effect of NO has attracted considerable attention, and efforts to deliver NO in a controlled manner, especially through polymeric carriers, has been the topic of much research. This naturally produced signaling molecule has stood out as a potentially more potent therapeutic agent compared to exogenously synthesized drugs. In this review, we will focus on past efforts of using the controlled release of NO via polymer-based materials to derive specific therapeutic results. We have also added studies and our future suggestions on co-delivery methods with other gasotransmitters as a step towards developing multifunctional carriers.

Near-infrared biophotonics-based nanodrug release systems and their potential application for neuro-disorders

INTRODUCTION

Near-infrared ray (NIR)-responsive 'smart' nanoagents allow spatial and temporal control over the drug delivery process, noninvasively, without affecting healthy tissues and therefore they possess high potential for on-demand, targeted drug/gene delivery. Various NIR-responsive drug/gene delivery techniques are under investigation for peripheral disorders (especially for cancer). Nonetheless, their potential not been extensively examined for brain biomedical application.

AREAS COVERED

This review focuses on NIR-responsive characteristics of different NIR-nanobiophotonics-based nanoagents and associated drug delivery strategies. Together with their ongoing applications for peripheral drug delivery, we have highlighted the opportunities, challenges and possible solutions of NIR-nanobiophotonics for potential brain drug delivery.

EXPERT OPINION

NIR-nanobiophotonics can be considered superior among all photo-controlled drug/gene delivery approaches. Future work should focus on coupling NIR with biocompatible nanocarriers to determine the physiological compatibility of this approach. Their applications should be extended beyond the peripheral body region to brain region. Transient or intermittent NIR exposure strategies may be more accommodating for brain physiological ambience in order to minimize or avoid the possible deleterious thermal effect. In addition, while most studies are centered around the first NIR spectral window (700-1000 nm), the potential of second (1100-1350 nm) and third (1600-1870 nm) windows must be explored.

Upconverting nanoparticles for the near infrared photoactivation of transition metal complexes: new opportunities and challenges in medicinal inorganic photochemistry

The article highlights the emergent use of upconverting nanoparticles as tools for the near infrared photoactivation of transition metal complexes, identifying opportunities and challenges of this approach in the context of medicinal inorganic chemistry.

NIR fluorescent organic nanoparticles for photoinduced nitric oxide delivery with self monitoring and real time reporting abilities

Nitric oxide photodonor (NOD) conjugated perylene tetracarboxylate ester (TPT) based fluorescent organic TPT(NOD)₄ nanoparticles (NPs) with aggregation induced NIR emission have shown photoinduced nitric oxide delivery along with a red to green emission transition.

Inorganic Nanocrystals Functionalized Mesoporous Silica Nanoparticles: Fabrication and Enhanced Bio-applications

Mesoporous SiO2 nanoparticles (MSNs) are one of the most promising materials for bio-related applications due to advantages such as good biocompatibility, tunable mesopores, and large pore volume. However, unlike the inorganic nanocrystals with abundant physical properties, MSNs alone lack functional features. Thus, they are not sufficiently suitable for bio-applications that require special functions. Consequently, MSNs are often functionalized by incorporating inorganic nanocrystals, which provide a wide range of intriguing properties. This review focuses on inorganic nanocrystals functionalized MSNs, both their fabrication and bio-applications. Some of the most utilized methods for coating mesoporous silica (mSiO2) on nanoparticles were summarized. Magnetic, fluorescence and photothermal inorganic nanocrystals functionalized MSNs were taken as examples to demonstrate the bio-applications. Furthermore, asymmetry of MSNs and their effects on functions were also highlighted.

Dopamine-mediated photothermal theranostics combined with up-conversion platform under near infrared light

An organic-inorganic hybrid core-shell nanostructure, based on mesoporous silica coated upconversion core-shell nanoparticles (NaGdF4:Yb,Er@NaGdF4:Yb@mSiO2-Dopa abbreviated here as UCNP@mSiO2-Dopa) that stably incorporates dopamine (Dopa) in the silica layer was introduced as a theranostic nanoplatform for optical imaging guided photothermal therapy (PTT) using NIR excitation. Silica-attaching polyethylenimine make the Dopa transforms into an active form (transferred Dopa) that strongly absorbs light under single 980 nm irradiation. We show that the activated UCNP@mSiO2-Dopa nanoplatform is able to produce a pronounced photothermal effect, that elevates water temperature from room temperature to 41.8 °C within 2 minutes, while concurrently emitting strong upconverted luminescence (UCL) for visualized guidance under 980 nm laser. In addition, we demonstrate the application of the same UCNP@mSiO2-Dopa nanoplatform for magnetic resonance imaging (MRI) and x-ray computed tomography (CT) enabled by the gadolinium (Gd) element contained in the UCNP. Importantly, the in vitro and in vivo anti-cancer therapeutic effects have been shown efficacious, implying the use of the described nanoplatform as an effective multi-modal imaging enabled PTT agent. Results from the in vivo biodistribution of UCNPs@mSiO2, cellular live/dead assay, and histologic analysis of main organs of treated mice, reveal that the UCNP@mSiO2-Dopa agents are bio-compatible with low toxicity.

An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation

Upconversion nanoparticle (UCNP)-mediated photoactivation is a new approach to remotely control bioeffectors with much less phototoxicity and with deeper tissue penetration. However, the existing instrumentation on the market is not readily compatible with upconversion application. Therefore, modifying the commercially available instrument is essential for this research. In this paper, we first illustrate the modifications of a conventional fluorimeter and fluorescence microscope to make them compatible for photon upconversion experiments. We then describe the synthesis of a near-infrared (NIR)-triggered caged protein kinase A catalytic subunit (PKA) immobilized on a UCNP complex. Parameters for microinjection and NIR photoactivation procedures are also reported. After the caged PKA-UCNP is microinjected into REF52 fibroblast cells, the NIR irradiation, which is significantly superior to conventional UV irradiation, efficiently triggers the PKA signal transduction pathway in living cells. In addition, positive and negative control experiments confirm that the PKA-induced pathway leading to the disintegration of stress fibers is specifically triggered by NIR irradiation. Thus, the use of protein-modified UCNP provides an innovative approach to remotely control light-modulated cellular experiments, in which direct exposure to UV light must be avoided.

Near infrared light triggered nitric oxide releasing platform based on upconversion nanoparticles for synergistic therapy of cancer stem-like cells

Near infrared (NIR) light-driven nitric oxide (NO) release nano-platform based on upconversion nanoparticles (UCNPs) and light sensitive NO precursor Roussin's black salt (RBS) was fabricated to generate NO upon 808nm irradiation. The application of 808nm laser as the excitation source could achieve better penetration depth and avoid overheating problem. The combination of UCNPs and RBS could realize the on-demand release of NO at desired time and location by simply controlling the output of NIR laser. Cellular uptake results showed that more nanoparticles were internalized in cancer stem-like cells (CSCs) rather than non-CSCs. Therefore, a synergistic cancer therapy strategy to eradicate both CSCs and non-CSCs simultaneously was developed. Traditional chemo-drug could inhibit non-CSCs but has low killing efficiency in CSCs. However, we found that the combination of NO and chemotherapy could efficiently inhibit CSCs in bulk cells, including inhibiting mammosphere formation ability, decreasing CD44⁺/CD24^- subpopulation and reducing tumorigenic ability. The mechanism studies confirmed that NO could not only induce apoptosis but also increase drug sensitivity by declining drug efflux in CSCs. This UCNPs-based platform may provide a new combinatorial strategy of NO and chemotherapy to improve cancer treatment.

Controllable release of nitric oxide and doxorubicin from engineered nanospheres for synergistic tumor therapy

NaYF₄:Yb,Er upconversion nanoparticles (UCNPs) capped with long-chain carboxylic acid were synthesized and then conjugated with chitosan (CS) in the aid of N-hydroxysuccinimide. The resultant nanocompound was integrated with doxorubicin (DOX) and Roussin's black salt (RBS), a photosensitive nitric oxide (NO) donor to produce stimuli-responsive UCNPs(DOX)@CS-RBS nanospheres as nanocarriers for controllable drug delivery. On the one hand, the encapsulated UCNPs can efficiently absorb NIR photons and convert them into visible photons to trigger NO release. On the other hand, the entrapped DOX can be released at lowered pH from the swollen nanospheres caused by stretched oleoyl-CS chains under acidic conditions. The UCNPs(DOX)@CS-RBS nanospheres exhibit great therapeutic efficacy, which is attributable to the combination of NO and DOX releases based on NO dose-dependent mechanisms. This study highlights the controllable release of NO and DOX from the same nanocarriers and the synergistic therapeutic effect on tumors, which could give new insights into improving cancer nanotherapeutics.

STATEMENT OF SIGNIFICANCE

In this paper, core-shell structured UCNPs(DOX)@CS-RBS nanospheres have been designed and synthesized via a step-by-step procedure. The stimuli-responsive UCNPs(DOX)@CS-RBS nanospheres act as nanocarriers for controllable drug delivery towards cancer therapy. The encapsulated UCNPs can efficiently absorb NIR photons and convert them into visible light to trigger NO release. Meanwhile, the entrapped DOX can be released from the swollen nanospheres caused by stretched oleoyl-CS chains at lowered pH typical of intracellular environment. Synergistic cancer therapy will be achieved through the combination of NO and DOX releases based on NO dose-dependent mechanisms. This study provides new drug nanocarriers with high antitumor efficacy for synergistic cancer therapy.

MRI-guided and ultrasound-triggered release of NO by advanced nanomedicine

Nitric oxide (NO) has been well identified as a specific free radical molecule possessing wide-ranging therapeutic effects. Targeted delivery and controlled release of NO are highly desired to realize precision gas therapy, but are still challenging owing to the non-targetability and uncontrollability of NO itself. Herein, we propose a new concept of MRI-guided and ultrasound-triggered gas release for precision gas therapy. Based on this concept, we develop a novel ultrasound-responsive BNN-type NO-releasing molecule (NORM) and an advanced rattle-type nano-carrier of superparamagnetic iron oxide-encapsulated mesoporous silica nanoparticles (SPION@hMSN), and use them to construct a new intelligent nanomedicine (BNN6-SPION@hMSN) for the first time. The BNN6-SPION@hMSN nanomedicine exhibits excellent passive tumor-targeting capability, high MRI-guided tumor localization performance and a unique ultrasound-triggered NO release profile. The tumor-targeted, MRI-guided and ultrasound-triggered release profiles of the developed nanomedicine enable the tumor site-specific controlled release of NO in favor of high-efficacy and safe NO gas therapy of tumor.

Ruthenium nitrosyl functionalized graphene quantum dots as an efficient nanoplatform for NIR-light-controlled and mitochondria-targeted delivery of nitric oxide combined with photothermal therapy

A mitochondria-targeting nanoplatform for near-infrared-light-controlled release of nitric oxide accompanied by photothermal therapy was developed, which consists of ruthenium nitrosyl functionalized N-doped graphene quantum dots and a triphenylphosphonium moiety. The nanoplatform demonstrated both in vitro and in vivo anti-tumor efficacy upon irradiation with 808 nm light.

In Situ Growth Strategy to Integrate Up-Conversion Nanoparticles with Ultrasmall CuS for Photothermal Theranostics

In the theranostic field, a near-infrared (NIR) laser is located in the optical window, and up-conversion nanoparticles (UCNPs) could be potentially utilized as the imaging agents with high contrast. Meanwhile, copper sulfide (CuS) has been proposed as a photothermal agent with increased temperature under a NIR laser. However, there is still no direct and effective strategy to integrate the hydrophobic UCNPs with CuS until now. Herein, we propose an in situ growth routine based on the hydrophobic core/shell UCNPs combined with ultrasmall water-soluble CuS triggered by single 808 nm NIR irradiation as the theranostic platform. Hydrophobic NaYF₄:Yb,Er@NaYF₄,Nd,Yb could be turned hydrophilic with highly dispersed and biocompatible properties through conjunction with transferred dopamine. The as-synthesized ultrasmall CuS (3 and 7 nm) served as a stable photothermal agent even after several laser-on/off cycles. Most importantly, comparing with the mix routine, the in situ growth routine to coat UCNPs with CuS is meaningful, and the platform is uniform and stable. Green luminescence-guided hyperthermia could be achieved under a single 808 nm laser, which was evidenced by in vitro and in vivo assays. This nanoplatform is applicable as a bioimaging and photothermal antitumor agent, and the in situ growth routine could be spread to other integration processes.

Lanthanide-Doped Upconversion Nanoparticles: Emerging Intelligent Light-Activated Drug Delivery Systems

The development of drug delivery systems (DDSs) using near infrared (NIR) light and upconversion nanoparticles (UCNPs) has generated intensive interest over the past five years. These NIR-initiated DDSs not only offer a high degree of spatial and temporal determination of therapeutic release but also provide precise control over the released dosage. Furthermore, these nanoplatforms confer several advantages over conventional light-based DDSs-NIR offers better tissue penetration depth and a reduced risk of cellular photo-damage caused by exposure to light at high-energy wavelengths (e.g., ultraviolet light, <400 nm). The development of DDSs that can be activated by low intensity NIR illumination is highly desirable to avoid exposing living tissues to excessive heat that can limit the in vivo application of these DDSs. This encompasses research in three directions: (i) enhancing the quantum yield of the UCNPs; (ii) incorporation of photo-responsive materials with red-shifted absorptions into the UCNPs; and (iii) tuning the UCNPs excitation wavelength. This review focuses on recent advances in the development of NIR-initiated DDS, with emphasis on the use of photo-responsive compounds and polymeric materials conjugated onto UCNPs. The challenges that limit UCNPs clinical applications, alongside with the aforementioned techniques that have emerged to overcome these limitations, are highlighted.

From curiosity to applications. A personal perspective on inorganic photochemistry

Over the past several decades, the photochemistry and photophysics of transition metal compounds has blossomed from a relatively niche topic to a major research theme. Applications arising from the elucidation of the fundamental principles defining this field now range from probing the rates and mechanisms of small molecules with metalloproteins to light activated molecular machines. Offered here is a personal perspective of metal complex photochemistry drawn from this author's long involvement with this field. Several examples are described. Topics include characterizing key excited states and tuning these to modify chemical reactivity and/or photoluminescence properties, as well as using photoreactions as an entry to reactive intermediates relevant to homogeneous catalysts. This is followed by discussions of applying these concepts to developing precursors and precursor-antenna conjugates for the photochemical delivery of small molecule bioregulators to physiological targets.

A Facile Approach to Upconversion Crystalline CaF2:Yb3+,Tm3+@mSiO2 Nanospheres for Tumor Therapy

A new facile approach, namely chemical-assisted sol-gel growth (CASGG), was successfully developed to induce the formation of fine CaF2:Yb3+, Tm3+ nanocrytals within the pore channels of mesoporous silica (mSiO2) nanoparticles. A series of upconversion photoluminescent crystalline CaF2:Yb3+,Tm3+@mSiO2 nanospheres with controlled diameters from ~65 nm to ~290 nm were fabricated. All nanospheres presented sound cyto-compatibility and unique ratiometric spectral monitoring functionalities for drug release kinetics. The nanospheres with smallest dimension (UCNP-2.5, ~65nm) induced the most sustained DOX release kinetics. More importantly, the in-vitro study demonstrated that the DOX loaded UCNP-2.5 nanopheres presented the strongest anti-cancer efficacy to MCF-7 human breast cancer cells due to its stronger penetration ability to cell nuclei due to the size effect.

Synergistic eradication of antibiotic-resistant bacteria based biofilms in vivo using a NIR-sensitive nanoplatform

In this work, a novel multifunctional NIR-sensitive nanoplatform has been developed for synergistic eradication of antibiotic-resistant bacteria based biofilms in vitro and in vivo. With high biocompatibility and an outstanding synergistic effect, our system provides a promising avenue to preventing and combating biofilm-associated infections.

Near-Infrared-Sensitive Materials Based on Upconverting Nanoparticles

The near-infrared (NIR) region of the spectrum is called the "therapeutic window" because NIR light can penetrate deeply into tissue. Therefore, NIR-sensitive materials are attractive for biomedical applications. Recently, upconverting nanoparticles (UCNPs) were used to construct NIR-sensitive materials. UCNPs convert NIR light to UV or visible light, which can trigger photoreactions of photosensitive materials. Here, how to use UCNPs to construct NIR-sensitive materials is introduced, applications of NIR-sensitive materials with a focus on biomedical applications are highlighted, and the associated challenges are discussed.

Upconverting Nanoparticles Prompt Remote Near-Infrared Photoactivation of Ru(II)-Arene Complexes

The synthesis and full characterisation (including X-ray diffraction studies and DFT calculations) of two new piano-stool Ru(II) -arene complexes, namely [(η(6) -p-cym)Ru(bpy)(m-CCH-Py)][(PF)6]2 (1) and [(η(6) -p-cym)Ru(bpm)(m-CCH-Py)][(PF)6]2 (2; p-cym=p-cymene, bpy=2,2'-bipyridine, bpm=2,2'-bipyrimidine, and m-CCH-Py=3-ethynylpyridine), is described and discussed. The reaction of the m-CCH-Py ligand of 1 and 2 with diethyl-3-azidopropyl phosphonate by Cu-catalysed click chemistry affords [(η(6) -p-cym)Ru(bpy)(P-Trz-Py)][(PF)6]2 (3) and [(η(6) -p-cym)Ru(bpm)(P-Trz-Py)][(PF)6]2 (4; P-Trz-Py=[3-(1-pyridin-3-yl-[1,2,3]triazol-4-yl)-propyl]phosphonic acid diethyl ester). Upon light excitation at λ=395 nm, complexes 1-4 photodissociate the monodentate pyridyl ligand and form the aqua adduct ions [(η(6) -p-cym)Ru(bpy)(H2O)](2+) and [(η(6) -p-cym)Ru(bpm)(H2O)](2+). Thulium -doped upconverting nanoparticles (UCNPs) are functionalised with 4, thus exploiting their surface affinity for the phosphonate group in the complex. The so-obtained nanosystem UCNP@4 undergoes near-infrared (NIR) photoactivation at λ=980 nm, thus producing the corresponding reactive aqua species that binds the DNA-model base guanosine 5'-monophosphate.

Tumor cell specific and lysosome-targeted delivery of nitric oxide for enhanced photodynamic therapy triggered by 808 nm near-infrared light

A novel cancer cell lysosome-targetable multifunctional NO-delivery nanoplatform (Lyso-Ru-NO@FA@C-TiO₂) (1) was developed.

Near infrared light-mediated photoactivation of cytotoxic Re(i) complexes by using lanthanide-doped upconversion nanoparticles

Photoactivation of cytotoxic Re(i) complexes by using lanthanide doped upconversion nanoparticles upon near infrared illumination was demonstrated to selectively activate Re(i) complexes in tumor cells for enhanced anti-cancer effect.

Using low-energy near infrared light and upconverting nanoparticles to trigger photoreactions within supramolecular assemblies

This overview highlights how the high-energy ultraviolet or visible light required to drive photochemical reactions can be overcome by integrating the chromophores into supramolecular structures containing upconverting nanoparticles with trivalent lanthanide dopants (such as Tm³⁺ and Er³⁺).

Biological signaling by small inorganic molecules

Small redox active molecules such as reactive nitrogen and oxygen species and hydrogen sulfide have emerged as important biological mediators that are involved in various physiological and pathophysiological processes. Advancement in understanding of cellular mechanisms that tightly regulate both generation and reactivity of these molecules is central to improved management of various disease states including cancer and cardiovascular dysfunction. Imbalance in the production of redox active molecules can lead to damage of critical cellular components such as cell membranes, proteins and DNA and thus may trigger the onset of disease. These small inorganic molecules react independently as well as in a concerted manner to mediate physiological responses. This review provides a general overview of the redox biology of these key molecules, their diverse chemistry relevant to physiological processes and their interrelated nature in cellular signaling.

A novel self-assembled sandwich nanomedicine for NIR-responsive release of NO

A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect.

Near-infrared light activated delivery platform for cancer therapy

Cancer treatment using conventional drug delivery platforms may lead to fatal damage to normal cells. Among various intelligent delivery platforms, photoresponsive delivery platforms are becoming popular, as light can be easily focused and tuned in terms of power intensity, wavelength, and irradiation time, allowing remote and precise control over therapeutic payload release both spatially and temporally. This unprecedented controlled delivery manner is important to improve therapeutic efficacy while minimizing side effects. However, most of the existing photoactive delivery platforms require UV/visible excitation to initiate their function, which suffers from phototoxicity and low level of tissue penetration limiting their practical applications in biomedicine. With the advanced optical property of converting near infrared (NIR) excitation to localized UV/visible emission, upconversion nanoparticles (UCNPs) have emerged as a promising photoactive delivery platform that provides practical applications for remote spatially and temporally controlled release of therapeutic payload molecules using low phototoxic and high tissue penetration NIR light as the excitation source. This article reviews the state-of-the-art design, synthesis and therapeutic molecular payload encapsulation strategies of UCNP-based photoactive delivery platforms for cancer therapy. Challenges and promises for engineering of advanced delivery platforms are also highlighted.

NIR-Responsive On-Demand Release of CO from Metal Carbonyl-Caged Graphene Oxide Nanomedicine

On-demand release of carbon monoxide (CO) is realized through a novel near-infrared-responsive nanomedicine in favor of the enhancement of therapy efficacy and biosafety of CO therapy.

Near infrared activation of an anticancer Pt(IV) complex by Tm-doped upconversion nanoparticles

The Pt(IV) complex cis,cis,trans-[Pt(NH3)2(Cl)2(O2CCH2CH2CO2H)2] is photoactivated by near infrared light (980 nm) using NaYF4:Yb(3+)/Tm(3+)@NaYF4 core-shell upconversion nanoparticles. Coupling of this cisplatin precursor with the biocompatible PEGylated phospholipid DSPE-PEG(2000)-NH2 affords a valuable approach to decorate the surface of the nanoparticles, providing novel photoactivatable nanomaterials capable of releasing Pt(II) species upon NIR light excitation.

Light or Heat? The Origin of Cargo Release from Nanoimpeller Particles Containing Upconversion Nanocrystals under IR Irradiation

Nanoimpellers are mesoporous silica nanoparticles that contain azobenzene derivatives bonded inside the pores and rely on the continuous photoisomerization of multiple azobenzenes to release cargo under near UV irradiation. A recent study employs upconversion nanocrystal embedded particles to replace UV light with IR light to stimulate nanoimpellers. However, the photothermal effect of IR irradiation and its likely contribution to the observed release behavior are not examined. It is found that, in the absence of upconversion nanocrystals, the azobenzene co-condensed silica particles still respond to 980 nm illumination, which increases the nanoparticle temperature by 25 °C in 15 min, experimentally measured by an encapsulated nanothermometer. After suppressing the heating, the IR irradiation does not initiate the release, indicating that optical heating, not upconverted light, is responsible for the triggered cargo release. The results are explained by numerical analyses.

Near-infrared light-responsive nanomaterials for cancer theranostics

Early diagnosis and effective cancer therapy are required, to properly treat cancer, which causes more than 8.2 million deaths in a year worldwide. Among various cancer treatments, nanoparticle-based cancer therapies and molecular imaging techniques have been widely exploited over the past decades to overcome current drawbacks of existing cancer treatments. In particular, gold nanoparticles (AuNPs), carbon nanotubes (CNTs), graphene oxide (GO), and upconversion nanocrystals (UNCs) have attracted tremendous attention from researchers due to their near-infrared (NIR) light-responsive behaviors. These nanomaterials are considered new multifunctional platforms for cancer theranostics. They would enable on-demand control of drug release or molecular imaging in response to a remote trigger by NIR light exposure. This approach allows the patient or physician to adjust therapy precisely to a target site, thus greatly improving the efficacy of cancer treatments, while reducing undesirable side effects. In this review, we have summarized the advantages of NIR light-responsive nanomaterials for in vivo cancer treatments, which includes NIR triggered photothermal therapy (PTT) and photodynamic therapy (PDT). Furthermore, recent developments, perspectives, and new challenges of NIR light-responsive nanomaterials are discussed for cancer theranostic applications.

Double-walled Au nanocage/SiO2 nanorattles: integrating SERS imaging, drug delivery and photothermal therapy

In this work, a novel type of nanomedical platform, the double-walled Au nanocage/SiO(2) nanorattle, is successfully fabricated by combining two "hollow-excavated strategies"--galvanic replacement and "surface-protected etching". The rational design of double-walled nanostructure based on gold nanocages (AuNCs) and hollow SiO(2) shells functionalized respectively with p-aminothiophenol (pATP) and Tat peptide simultaneously renders the nanoplatforms three functionalities: 1) the whole nanorattle serves as a high efficient drug carrier thanks to the structural characteristics of AuNC and SiO(2) shell with hollow interiors and porous walls; 2) the AuNC with large electromagnetic enhancement acts as a sensitive surface-enhanced Raman scattering (SERS) substrate to track the internalization process of the nanorattles by human MCF-7 breast cancer cells, as well as an efficient photothermal transducer for localized hyperthermia cancer therapy due to the strong near-infrared absorption; 3) Tat-functionalized SiO(2) shell not only improves biocompatibility and cell uptake efficiency resulting in enhanced anticancer efficacy but also prevents the AuNCs from aggregation and provides the stability of AuNCs so that the SERS signals can be used for cell tracking in high fidelity. The reported chemistry and the designed nanostructures should inspire more interesting nanostructures and applications.

Current advances in lanthanide ion (Ln3+)-based upconversion nanomaterials for drug delivery

This review mainly focuses on the recent advances in various chemical syntheses of Ln³⁺-based upconversion nanomaterials, with special emphasis on their application in stimuli-response controlled drug release and subsequent therapy.

Upconversion nanoparticles as versatile light nanotransducers for photoactivation applications

Upconversion nanoparticles enable use of near infrared light for spatially and temporally controlled activation of therapeutic compounds in deeper tissues.

Design of hybrid nanovehicles for remotely triggered drug release: an overview

This review addresses the advantages of remote triggers, e.g. ultrasounds, near infrared light and alternating magnetic fields, the fabrication of the hybrid nanovehicles, the release mechanisms and the next challenges.

Mesoporous NaYF4:Yb,Er@Au–Pt(iv)-FA nanospheres for dual-modal imaging and synergistic photothermal/chemo-anti-cancer therapy

Mesoporous NaYF₄:Yb,Er@Au–Pt(iv)-FA up-conversion nanoparticles have been designed for dual-modal imaging-guided anti-cancer therapy, and show excellent inhibition toward cancer cells due to the synergistic photothermal/chemo-therapy.

Lab on upconversion nanoparticles: optical properties and applications engineering via designed nanostructure

This review aims to summarize recent progress in optical properties and applications engineering of upconversion nanoparticles via the designed nanostructure.

A photoCORM nanocarrier for CO release using NIR light

Amphiphilic polymer conjugates with upconverting nanoparticles serve as water-soluble nanocarriers for NIR-photochemical delivery of CO from hydrophobic photoCORMS.