Theranostic Materials Research Articles

An NAD(P)H:quinone oxidoreductase 1 (NQO1) enzyme responsive nanocarrier based on mesoporous silica nanoparticles for tumor targeted drug delivery in vitro and in vivo.

quinone oxidoreductase 1 (NQO1) enzyme responsive nanocarrier based on mesoporous silica nanoparticles (MSNPs) for on-command delivery applications has been described in this paper. Gatekeeping of MSNPs is achieved by the integration of mechanically interlocked rotaxane nanovalves on the surface of MSNPs. The rotaxane nanovalve system is composed of a linear stalk anchoring on the surface of MSNPs, an α-cyclodextrin ring that encircles it and locks the payload "cargo" molecules in the mesopores, and a benzoquinone stopper incorporated at the end of the stalk. The gate opening and controlled release of the cargo are triggered by cleavage of the benzoquinone stopper using an endogenous NQO1 enzyme. In addition to having efficient drug loading and controlled release mechanisms, this smart biocompatible carrier system showed obvious uptake and consequent release of the drug in tumor cells, could selectively induce the tumor cell death and enhance the capability of inhibition of tumor growth in vivo. The controlled drug delivery system demonstrated its use as a potential theranostic material.

Dysprosium-containing layered double hydroxides nanoparticles intercalated with biologically active species as an approach for theranostic systems

Abstract A layered double hydroxide structure including dysprosium cations was prepared by co-precipitation. The nanoparticles showed a linear relationship with the reciprocal relaxation spin-lattice (T1) time of water protons which is reflected as contrast in aqueous suspensions analyzed by magnetic resonance imaging. The interlayer space of dysprosium containing LDH was successfully intercalated with folate, ibuprofen and gallate ions, which are key molecules for recognition of some cancer cells and treatment of diseases. The paramagnetic property of the dysprosium-containing LDH detected in this work beside the ability to transport drugs open up the opportunity to design theranostic materials in a single crystal phase with nanometric dimensions.

Hybrid Theranostic Platform for Second Near-IR Window Light Triggered Selective Two-Photon Imaging and Photothermal Killing of Targeted Melanoma Cells.

Despite advances in the medical field, even in the 21st century cancer is one of the leading causes of death for men and women in the world. Since the second near-infrared (NIR) biological window light between 950 and 1350 nm offers highly efficient tissue penetration, the current article reports the development of hybrid theranostic platform using anti-GD2 antibody attached gold nanoparticle (GNP) conjugated, single-wall carbon nanotube (SWCNT) for second near-IR light triggered selective imaging and efficient photothermal therapy of human melanoma cancer cell. Reported results demonstrate that due to strong plasmon-coupling, two-photon luminescence (TPL) intensity from theranostic GNP attached SWCNT materials is 6 orders of magnitude higher than GNP or SWCNT alone. Experimental and FDTD simulation data indicate that the huge enhancement of TPL intensity is mainly due to strong resonance enhancement coupled with the stronger electric field enhancement. Due to plasmon coupling, the theranostic material serves as a local nanoantennae to enhance the photothermal capability via strong optical energy absorption. Reported data show that theranostic SWCNT can be used for selective two-photon imaging of melanoma UACC903 cell using 1100 nm light. Photothermal killing experiment with 1.0 W/cm(2) 980 nm laser light demonstrates that 100% of melanoma UACC903 cells can be killed using theranostic SWCNT bind melanoma cells after just 8 min of exposure. These results demonstrate that due to plasmon coupling, the theranostic GNP attached SWCNT material serves as a two-photon imaging and photothermal source for cancer cells in biological window II.

Bioinspired photonic structures by the reflector layer of firefly lantern for highly efficient chemiluminescence.

Fireflies have drawn considerable attention for thousands of years due to their highly efficient bioluminescence, which is important for fundamental research and photonic applications. However, there are few reports on the reflector layer (RL) of firefly lantern, which contributes to the bright luminescence. Here we presented the detailed microstructure of the RL consisting of random hollow granules, which had high reflectance in the range from 450 nm to 800 nm. Inspired by the firefly lantern, artificial films with high reflectance in the visible region were fabricated using hollow silica microparticles mimicking the structure of the RL. Additionally, the bioinspired structures provided an efficient RL for the chemiluminescence system and could substantially enhance the initial chemiluminescence intensity. The work not only provides new insight into the bright bioluminescence of fireflies, but also is importance for the design of photonic materials for theranostics, detection, and imaging.

When 1+1>2: Nanostructured composites for hard tissue engineering applications.

Multicomponent, synergistic and multifunctional nanostructures have taken over the spotlight in the realm of biomedical nanotechnologies. The most prospective materials for bone regeneration today are almost exclusively composites comprising two or more components that compensate for the shortcomings of each one of them alone. This is quite natural in view of the fact that all hard tissues in the human body, except perhaps the tooth enamel, are composite nanostructures. This review article highlights some of the most prospective breakthroughs made in this research direction, with the hard tissues in main focus being those comprising bone, tooth cementum, dentin and enamel. The major obstacles to creating collagen/apatite composites modeled after the structure of bone are mentioned, including the immunogenicity of xenogeneic collagen and continuously failing attempts to replicate the biomineralization process in vitro. Composites comprising a polymeric component and calcium phosphate are discussed in light of their ability to emulate the soft/hard composite structure of bone. Hard tissue engineering composites created using hard material components other than calcium phosphates, including silica, metals and several types of nanotubes, are also discoursed on, alongside additional components deliverable using these materials, such as cells, growth factors, peptides, antibiotics, antiresorptive and anabolic agents, pharmacokinetic conjugates and various cell-specific targeting moieties. It is concluded that a variety of hard tissue structures in the body necessitates a similar variety of biomaterials for their regeneration. The ongoing development of nanocomposites for bone restoration will result in smart, theranostic materials, capable of acting therapeutically in direct feedback with the outcome of in situ disease monitoring at the cellular and subcellular scales. Progress in this research direction is expected to take us to the next generation of biomaterials, designed with the purpose of fulfilling Daedalus' dream - not restoring the tissues, but rather augmenting them.

Cyto/hemocompatible magnetic hybrid nanoparticles (Ag2S–Fe3O4) with luminescence in the near-infrared region as promising theranostic materials

Small hybrid nanoparticles composed of highly biocompatible Ag2S quantum dots (QD) emitting in the near-infrared region and superparamagnetic iron oxide (SPION) are produced in a simple extraction method utilizing ligand exchange mechanism. Hybrid nanoparticles luminesce at the same wavelength as the parent QD, therefore an array of hybrid nanoparticles with emission between 840 and 912nm were easily produced. Such hybrid structures have (1) strong luminescence in the medical imaging window eliminating the autofluoresence of cells as effective optical probes, (2) strong magnetic response for magnetic targeting and (3) good cyto/hemocompatibility. An interesting size dependent cytotoxicity behavior was observed in HeLa and NIH/3T3 cell lines: smallest particles are internalized significantly more by both of the cell lines, yet showed almost no significant cytotoxicity in HeLa between 10 and 25μg/mL Ag concentration but were most toxic in NIH/3T3 cells. Cell internalization and hence the cytotoxicity enhanced when cells were incubated with the hybrid nanoparticles under magnetic field, especially with the hybrid nanoparticles containing larger amounts of SPION in the hybrid composition. These results prove them as effective optical imaging agents and magnetic delivery vehicles. Combined with the known advantages of SPIONs as a contrast agent in MRI, these particles are a step forward for new theranostics for multimode imaging and magnetic targeting.

Peptides for specifically targeting nanoparticles to cellular organelles: quo vadis?

The interfacing of nanomaterials and especially nanoparticles within all aspects of biological research continues to grow at a nearly unabated pace with projected applications focusing on powerful new tools for cellular labeling, imaging, and sensing, theranostic materials, and drug delivery. At the most fundamental level, many of these nanoparticles are meant to target not only very specific cell-types, regardless of whether they are in a culture, tissue, an animal model, or ultimately a patient, but also in many cases a specific subcellular organelle. During this process, these materials will undergo a complex journey that must first find the target cell of interest, then be taken up by those cells across the extracellular membrane, and ultimately localize to a desired subcellular organelle, which may include the nucleus, plasma membrane, endolysosomal system, mitochondria, cytosol, or endoplasmic reticulum. To accomplish these complex tasks in the correct sequence, researchers are increasingly interested in selecting for and exploiting targeting peptides that can impart the requisite capabilities to a given nanoparticle construct. There are also a number of related criteria that need careful consideration for this undertaking centering on the nature and properties of the peptide vector itself, the peptide-nanoparticle conjugate characteristics, and the target cell. Here, we highlight some important issues and key research areas related to this burgeoning field. We begin by providing a brief overview of some criteria for optimal attachment of peptides to nanoparticles, the predominant methods by which nanoparticles enter cells, and some of the peptide sequences that have been utilized to facilitate nanoparticle delivery to cells focusing on those that engender the initial targeting and uptake. Because almost all materials delivered to cells by peptides utilize the endosomal system of vesicular transport and in many cases remain sequestered within the vesicles, we critically evaluate the issue of endosomal escape in the context of some recently reported successes in this regard. Following from this, peptides that have been reported to deliver nanoparticles to specific subcellular compartments are examined with a focus on what they delivered and the putative mechanisms by which they were able to accomplish this. The last section focuses on two areas that are critical to realizing this overall approach in the long term. The first is how to select for peptidyl sequences capable of improved or more specific cellular or subcellular targeting based upon principles commonly associated with drug discovery. The second looks at what has been done to create modular peptides that incorporate multiple desirable functionalities within a single, contiguous sequence. This provides a viable alternative to either the almost insurmountable challenge of finding one sequence capable of all functions or, alternatively, attaching different peptides with different functionalities to the same nanoparticle in different ratios when trying to orchestrate their net effects. Finally, we conclude with a brief perspective on the future evolution and broader impact of this growing area of bionanoscience.

Highly luminescent and cytocompatible cationic Ag2S NIR-emitting quantum dots for optical imaging and gene transfection

The development of non-toxic theranostic nanoparticles capable of delivering a therapeutic cargo and providing a means for diagnosis is one of the most challenging tasks in nano-biotechnology. Gene therapy is a very important mode of therapy and polyethyleneimine (PEI) is one of the most successful vehicles for gene transfection, yet poses significant toxicity. Optical imaging utilizing quantum dots is one of the newer but fast growing diagnostic modalities, which requires non-toxic, highly luminescent materials, preferentially active in the near infrared region. Ag2S NIRQDs fit to this profile perfectly. Here, we demonstrate the aqueous synthesis of cationic Ag2S NIRQDs with a mixed coating of 2-mercaptopropionic acid (2MPA) and PEI (branched, 25 kDa), which are highly luminescent in the NIR-I window (λem = 810-840 nm) as new theranostic nanoparticles. Synergistic stabilization of the QD surface via the simultaneous use of a small molecule and a polymeric material provided the highest quantum yield, 150% (with respect to LDS 798 at pH 7.4), reported in the literature for Ag2S. These cationic particles show a dramatic improvement in cytocompatibility even without PEGylation, a strong optical signal easily detected by confocal laser microscopy and effective conjugation and transfection of the green fluorescence protein plasmid (pGFP) to HeLa and MCF-7 cell lines (40% efficiency). Overall, these Ag2S NIRQDs show great potential as new theranostics.

Aqueous synthesis of polyhedral "brick-like" iron oxide nanoparticles for hyperthermia and T2 MRI contrast enhancement.

A low temperature, aqueous synthesis of polyhedral iron oxide nanoparticles (IONPs) is presented. The modification of the co-precipitation hydrolysis method with Triton X surfactants results in the formation of crystalline polyhedral particles. The particles are herein termed iron oxide "nanobricks" (IONBs) as the variety of particles made are all variations on a simple "brick-like" rhombohedral shape as evaluated by TEM. These IONBs can be easily coated with hydrophilic silane ligands, allowing them to be dispersed in aqueous media. The dispersed particles are investigated for potential applications as hyperthermia and T2 MRI contrast agents. The results demonstrate that the IONBs perform better than comparable spherical IONPs in both applications, and show r2 values amongst the highest for iron oxide based materials reported in the literature.

Theranostic USPIO-Loaded Microbubbles for Mediating and Monitoring Blood-Brain Barrier Permeation.

Efficient and safe drug delivery across the blood-brain barrier (BBB) remains to be one of the major challenges of biomedical and (nano-) pharmaceutical research. Here, we show that poly(butyl cyanoacrylate)-based microbubbles (MB), carrying ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles within their shell, can be used to mediate and monitor BBB permeation. Upon exposure to transcranial ultrasound pulses, USPIO-MB are destroyed, resulting in acoustic forces inducing vessel permeability. At the same time, USPIO are released from the MB shell, they extravasate across the permeabilized BBB and they accumulate in extravascular brain tissue, thereby providing non-invasive R2*-based magnetic resonance imaging information on the extent of BBB opening. Quantitative changes in R2* relaxometry were in good agreement with 2D and 3D microscopy results on the extravascular deposition of the macromolecular model drug FITC-dextran into the brain. Such theranostic materials and methods are considered to be useful for mediating and monitoring drug delivery across the BBB, and for enabling safe and efficient treatment of CNS disorders.

Multivalent polymers for drug delivery and imaging: the challenges of conjugation.

Multivalent polymers offer a powerful opportunity to develop theranostic materials on the size scale of proteins that can provide targeting, imaging, and therapeutic functionality. Achieving this goal requires the presence of multiple targeting molecules, dyes, and/or drugs on the polymer scaffold. This critical review examines the synthetic, analytical, and functional challenges associated with the heterogeneity introduced by conjugation reactions as well as polymer scaffold design. First, approaches to making multivalent polymer conjugations are discussed followed by an analysis of materials that have shown particular promise biologically. Challenges in characterizing the mixed ligand distributions and the impact of these distributions on biological applications are then discussed. Where possible, molecular-level interpretations are provided for the structures that give rise to the functional ligand and molecular weight distributions present in the polymer scaffolds. Lastly, recent strategies employed for overcoming or minimizing the presence of ligand distributions are discussed. This review focuses on multivalent polymer scaffolds where average stoichiometry and/or the distribution of products have been characterized by at least one experimental technique. Key illustrative examples are provided for scaffolds that have been carried forward to in vitro and in vivo testing with significant biological results.

Design of functional nanoparticles and assemblies for theranostic applications.

Nanostructured materials have found increasing applications in medical therapies and diagnostics (theranostics). The main challenge is the ability to impart the nanomaterials with structurally tailored functional properties which can effectively target biomolecules but also provide signatures for effective detection. The harnessing of functional nanoparticles and assemblies serves as a powerful strategy for the creation of the structurally tailored multifunctional properties. This article highlights some of the important design strategies in recent investigation of metals (especially gold and silver), and magnetically functionalized nanoparticles, and molecularly assembled or biomolecularly conjugated nanoparticles with tunable optical, spectroscopic, magnetic, and electrical properties for applications in several areas of potential theranostic interests. Examples include colorimetric detection of amino acids and small peptides, surface-enhanced Raman scattering detection of biomolecular recognition of proteins and DNAs, delivery in cell transfection and bacteria inactivation, and chemiresistive detection of breath biomarkers. A major emphasis is placed on understanding how the control of the nanostructures and the molecular and biomolecular interactions impact these biofunctional properties, which has important implications for bottom-up designs of theranostic materials.

Functionalized polymeric nanoparticles loaded with indocyanine green as theranostic materials for targeted molecular near infrared fluorescence imaging and photothermal destruction of ovarian cancer cells.

Ovarian cancer remains the deadliest malignancy of the female reproductive system. The ability to identify and destroy all ovarian tumor nodules may have a termendous impact on preventing tumor recurrence, and patient survival. The objective of this study is to investigate the effectiveness of a nano-structured system for combined near infrared (NIR) fluorescence imaging of human epidermal growth factor receptor-2 (HER2) over-expression, as a biomarker of ovarian cancer cells, and photothermal destruction of these cells in vitro. The nano-structured system consists of the near infrared dye, indocyanine green (ICG), encapsulated within poly(allylamine) hydrochloride chains cross-linked ionically with sodium phosphate. The surface of the construct is functionalized by covalently attached polyethylene glycol, and monoclonal antibodies against HER2 using reducitve amination methods. We use dynamic light scattering, and absorption and fluorescence spectroscopy for phyiscal characterization of the constructs. Flow cytometry and fluorescence microscopy are used to investigate molecular targeting and imaging capabilities of the constructs against SKOV3 and OVCAR3 ovarian cancer cell lines, which have relatively high and low expression levels of the HER2 receptor, respectively. Continuous NIR laser irradiation at 808 nm is used to investigating the utility of the constructs in mediating photothermal destruction of SKOV3 cells. Flow cytometry results indicate that the functionalized nano-constructs are more effective in targeting the HER2 receptor than non-encapsulated ICG and non-functionlaized constructs (P < 0.005). Fluorescence microscopic images show the capaiblity of the functionalized constructs in NIR imaging of HER2 overexpression. The functionalized nano-constructs are also capable of inducing a significantly greater increase in photothermal destruction of SKOV3 cells than free ICG and non-functionalized constructs (P < 0.005). We have demonstrated the efficacy of polymeric nano-structured constructs loaded with ICG, and functionalized with the monoclonal antibodies, as thernaostic materials for targted molecular NIR imaging of the HER2 receptor overexpression on ovarian cancer cells, and photothermal destruction of these cells. These nanoparticles may prove useful towards intraoperative detection, imaging, and phototherapy of small ovarian cancer nodules.

Oligoamine-tethered low generation polyamidoamine dendrimers as potential nucleic acid carriers.

In recent years, dendrimers have emerged as the most widely explored materials for theranostics emphasizing their potential in therapeutic delivery and diagnostics as well as in pharmaceutical technology. Amongst them, PAMAM dendrimers have been extensively studied for their prospects in various biomedical applications due to their defined structures and distinctive features such as monodispersity, uniformity and amenability to functionalization. Here, low generation PAMAM dendrimers (G2-G4) have been modified via Michael addition reaction followed by amidation with an oligoamine linker, tetraethylenepentamine (TEPA). Subsequently, these modified dendrimers were characterized by physicochemical techniques and evaluated for their capability to transfer nucleic acids in vitro. The results displayed significant improvements in the transfection efficiency in both HeLa and A549 cells maintaining higher cell viability. Sequential delivery of GFP-specific siRNA resulted in ∼73% suppression of the target gene. Flow cytometry results revealed that one of the formulations, mG3-pDNA complex, exhibited the highest gene transfection (∼49-68%) outperforming pDNA complexes of native dendrimers and the standard transfection reagent, Superfect (∼32-36%). All these results ensure the potential of the modified dendrimers as effective vectors for future gene delivery applications.

Simultaneous RGB Emitting Au Nanoclusters in Chitosan Nanoparticles for Anticancer Gene Theranostics

Advanced theranostic materials hold promise for targeted delivery of drugs, with the ability to follow the transport as well as its consequences. This should, ideally, be possible with minimum invasive surgery and having no or minimum cytotoxicity of the materials. It requires development of newer materials whose physical properties would allow for easy probe, which could carry the therapeutic molecules, which will be stable under physiological conditions, and at the same time would be able to permeate barriers to the target. We report the development of a composite consisting of highly fluorescent Au nanoclusters and the biopolymer chitosan, which could easily be converted into nanoparticles and would form a stable polyplex with suicide gene for induction of apoptosis in cervical cancer cells. The simultaneous red, green, and blue fluorescence from the nanoclusters provided convenient optical imaging and flow cytometry probes, without having to use additional dyes. Moreover, the colloidal nanocluster-polymer composite could be converted into solid film and be stored with the retention of optical properties. The pH tunable optical properties in the medium were also intact in the films that quickly dissolved in water with retention of properties.

Erythrocyte-derived photo-theranostic agents: hybrid nano-vesicles containing indocyanine green for near infrared imaging and therapeutic applications

Development of theranostic nano-constructs may enable diagnosis and treatment of diseases at high spatial resolution. Some key requirements for clinical translation of such constructs are that they must be non-toxic, non-immunogenic, biodegradable, with extended circulating lifetime. Cell-based structures, particularly those derived from erythrocytes, are promising candidate carrier systems to satisfy these requirements. One particular type of theranostic materials utilize light-sensitive agents that once photo-activated can provide diagnostic imaging capability, and elicit therapeutic effects. Here we demonstrate the first successful engineering of hybrid nano-scale constructs derived from membranes of hemoglobin-depleted erythrocytes that encapsulate the near infrared chromophore, indocyanine green. We show the utility of the constructs as photo-theranostic agents in fluorescence imaging and photothermal destruction of human cells. These erythrocyte-mimicking nano-structures can be derived autologously, and may have broad applications in personal nanomedicine ranging from imaging and photo-destruction of cancerous tissues to vascular abnormalities, and longitudinal evaluations of therapeutic interventions.

Theranostic Magnetic Core–Plasmonic Shell Star Shape Nanoparticle for the Isolation of Targeted Rare Tumor Cells from Whole Blood, Fluorescence Imaging, and Photothermal Destruction of Cancer

Cancer is one of the most life-threatening diseases, which causes 7.6 million deaths and around 1 trillion dollars economic loss every year. Theranostic materials are expected to improve early detection and safe treatment through personalized medicine. Driven by the needs, we report the development of a theranostic plasmonic shell-magnetic core star shape nanomaterial based approach for the targeted isolation of rare tumor cells from the whole blood sample, followed by diagnosis and photothermal destruction. Experimental data with whole blood sample spiked with SK-BR-3 cancer cell shows that Cy3 attached S6 aptamer conjugated theranostic plasmonic/magnetic nanoparticles can be used for fluorescence imaging and magnetic separation even in 0.001% mixtures. A targeted photothermal experiment using 1064 nm near-IR light at 2-3 W/cm(2) for 10 min resulted in selective irreparable cellular damage to most of the SK-BR-3 cancer cells. We discuss the possible mechanism and operating principle for the targeted imaging, separation, and photothermal destruction using theranostic magnetic/plasmonic nanotechnology. After the optimization of different parameters, this theranostic nanotechnology-driven assay could have enormous potential for applications as contrast agent and therapeutic actuators for cancer.

Dendritic Nanoparticles: the Next Generation of nanocarriers?

Dendritic polymers have attracted a great deal of scientific interest due to their well-defined unique structure and capability to be multifunctionalized. Here we present a comprehensive overview of various dendrimer-based nanomaterials that are currently being investigated for therapeutic delivery and diagnostic applications. Through a critical review of the old and new dendritic designs, we highlight the advantages and disadvantages of these systems and their structure-biological property relationships. This article also focuses on the major challenges facing the clinical translation of these nanomaterials and how these challenges are being (or should be) addressed, which will greatly benefit the overall progress of dendritic materials for theranostics.

Theranostic Systems and Strategies for Monitoring Nanomedicine-Mediated Drug Targeting

Nanomedicine formulations are considered to be superior to standard low-molecular-weight drugs because of an increased drug accumulation at the pathological site and a decreased localization to healthy non-target tissues, together leading to an improved balance between the efficacy and the toxicity of (chemo-) therapeutic interventions. To better understand and further improve nanomedicine-mediated drug targeting, it is important to design systems and strategies which are able to provide real-time feedback on the localization, the release and the therapeutic efficacy of these formulations. The advances made over the past few years with regard to the development of novel imaging agents and techniques have provided a broad basis for the design of theranostic nanomedicine materials, i.e. multicomponent carrier constructs in which drugs and imaging agents are combined, and which can be used to address issues related to drug localization, drug release and drug efficacy. Here, we summarize several recent efforts in this regard, and we show that theranostic systems and strategies hold significant potential for monitoring and improving nanomedicine-mediated drug targeting.

Development of a pH sensitive nanocarrier using calcium phosphate coated gold nanoparticles as a platform for a potential theranostic material

Methoxy-poly(ethylene glycol) (mPEG)-Asp-Cys was synthesized by ring opening polymerization, and its characterization by 1H nuclear magnetic resonance (NMR) showed that the copolymer has 18 aspartic acid units and 0.95 cysteine units on average, with the molecular weight and distribution of 13.1 k and 1.15. PEGylated AuNP with doxorubicin containing CaP layers was prepared to have the size of 79.8±18.7 nm by light scattering measurement method, with the CaP thickness around 27 nm. PEGylated Dox-AuNP@CaP was stable in the physiological conditions for several weeks in the presence of glutathione. Loading amount and efficiency of doxorubicin into the particles were 1.3% and 27.9%, respectively. The loading amount was 1.3%, lower than common organic selfassembled carriers, because of the relatively high atomic mass of gold. In vitro release experiments were performed in two different environments: extracellular fluid (pH 7.4) and intracellular lyosomal fluid (pH 4.5). The amount of released doxorubicin from PEGylated Dox-AuNP, without CaP layer, exceeds 60% in 2 h. In contrast, PEGylated Dox-AuNP@CaP effectively limited the doxorubicin release in the extracellular condition to 13% after 12 h, and changing the media to the intracellular lysosomal condition resulted in a triggered release of doxorubicin from 7% to 78% in an additional 4 h. Cell viability of PEGylated Dox-AuNP@CaP and PEGylated AuNP@CaP were estimated with HeLa cells by MTT assay. Cell viability of PEGylated Dox-AuNP@CaP came down to 19% after 24 h incubation, while the PEGylated AuNP@CaP particle itself showed slight cytotoxicity with the same conditions. The prepared PEGylated Dox-AuNP@CaP worked as a pH- and ion concentration-sensitive drug-delivery system as well as theranostic nanoparticles for CT imaging and cancer treatment. Open image in new window