Porphyrin–Lipid Stabilized Gold Nanoparticles for Surface Enhanced Raman Scattering Based Imaging

Designing SERS nanotags for profiling overexpressed surface markers on single cancer cells: A review

This review focuses on the chemical design and the use of Surface-Enhanced Raman Scattering (SERS)-active nanotags for measuring surface markers that can be overexpressed at the surface of single cancer cells. Indeed, providing analytical tools with true single-cell measurements capabilities is capital, especially since cancer research is increasingly leaning toward single-cell analysis, either to guide treatment decisions or to understand complex tumor behaviour including the single-cell heterogeneity and the appearance of treatment resistance. Over the past two decades, SERS nanotags have triggered significant interest in the scientific community owing their advantages over fluorescent tags, mainly because SERS nanotags resist photobleaching and exhibit sharper signal bands, which reduces possible spectral overlap and enables the discrimination between the SERS signals and the autofluorescence background from the sample itself. The extensive efforts invested in harnessing SERS nanotags for biomedical purposes, particularly in cancer research, highlight their potential as the next generation of optical labels for single-cell studies. The review unfolds in two main parts. The first part focuses on the structure of SERS nanotags, detailing their chemical composition and the role of each building block of the tags. The second part explores applications in measuring overexpressed surface markers on single-cells. The latter encompasses studies using single nanotags, multiplexed measurements, quantitative information extraction, monitoring treatment responses, and integrating phenotype measurements with SERS nanotags on single cells isolated from complex biological matrices. This comprehensive review anticipates SERS nanotags to persist as a pivotal technology in advancing single-cell analytical methods, particularly in the context of cancer research and personalized medicine.

Biomimetic Gold Nanorods-Manganese Porphyrins with Surface-Enhanced Raman Scattering Effect for Photoacoustic Imaging-Guided Photothermal/Photodynamic Therapy

Surface-enhanced Raman scattering (SERS) imaging integrating photothermal and photodynamic therapy (PTT/PDT) is a promising approach for achieving accurate diagnosis and effective treatment of cancers. However, most available Raman reporters show multiple signals in the fingerprint region, which overlap with background signals from cellular biomolecules. Herein, a 4T1 cell membrane-enveloped gold nanorods-manganese porphyrins system (GMCMs) is designed and successfully fabricated as a biomimetic theranostic nanoplatform. Manganese porphyrins are adsorbed on the surface of Au nanorods via the terminal alkynyl group. Cell membrane encapsulation protects the manganese porphyrins from falling off the gold nanorods. The biomimetic GMCMs confirm specific homologous targeting to 4T1 cells with good dispersibility, excellent photoacoustic (PA) imaging properties, and preferable photothermal and 1O2 generation performance. GMCMs exhibit distinct SERS signals in the silent region without endogenous biomolecule interference both in vitro and in vivo. Manganese ions could not only quench the fluorescence of porphyrins to enhance the SERS imaging effect but also deplete cellular GSH to increase 1O2 yield. Both in vitro and in vivo studies demonstrate that GMCMs effectively eradicate tumors through SERS/PA imaging-guided PTT/PDT. This study provides a feasible strategy for augmenting the Raman imaging effects of the alkynyl group and integrating GSH-depletion to enhance PTT/PDT efficacy.

Biomimetic Surface-Enhanced Raman Scattering Nanoparticles with Improved Dispersibility, Signal Brightness, and Tumor Targeting Functions

The development of biocompatible and nontoxic surface-enhanced Raman scattering (SERS) nanoparticles is of considerable current interest because of their attractive biomedical applications such as ultrasensitive in vitro diagnostics, in vivo tumor imaging, and spectroscopy-guided cancer surgery. However, current SERS nanoparticles are prepared and stored in aqueous solution, have limited stability and dispersibility, and are not suitable for lyophilization and storage by freeze-drying or other means. Here, we report a simple but robust method to coat colloidal SERS nanoparticles by naturally derived biomimetic red blood cell membranes (RBCM), leading to a dramatic improvement in stability and dispersibility under freeze-thawing, lyophilization, heating, and physiological conditions. The results demonstrate that the lyophilized SERS nanoparticles in the solid form can be readily dissolved and dispersed in physiological buffer solutions. A surprising finding is that the RBCM-coated SERS particles are considerably brighter (by as much as 5-fold) than PEGylated SERS particles under similar experimental conditions. This additional enhancement is believed to arise from the hydrophobic nature of RBCM's hydrocarbon chains, which is known to reduce electronic dampening and boost electromagnetic field enhancement. A further advantage in using biomimetic membrane coatings is that the bilayer membrane structure allows nonvalent insertion of molecular ligands for tumor targeting. In particular, we show that cyclic-RGD, a tumor-targeting peptide, can be efficiently inserted into the membrane coatings of SERS nanoparticles for targeting the ανβ3 integrin receptors expressed on cancer cells. Thus, biomimetic RBCMs provide major advantages over traditional polyethylene glycols for preparing SERS nanoparticles with improved dispersibility, higher signal intensity, and more efficient biofunctionalization.

Designing the Surface Chemistry of Inorganic Nanocrystals for Cancer Imaging and Therapy

Inorganic nanocrystals, such as gold, iron oxide and semiconductor quantum dots, offer promising prospects for cancer diagnostics, imaging and therapy, due to their specific plasmonic, magnetic or fluorescent properties. The organic coating, or surface ligands, of these nanoparticles ensures their colloidal stability in complex biological fluids and enables their functionalization with targeting functions. It also controls the interactions of the nanoparticle with biomolecules in their environment. It therefore plays a crucial role in determining nanoparticle biodistribution and, ultimately, the imaging or therapeutic efficiency. This review summarizes the various strategies used to develop optimal surface chemistries for the in vivo preclinical and clinical application of inorganic nanocrystals. It discusses the current understanding of the influence of the nanoparticle surface chemistry on its colloidal stability, interaction with proteins, biodistribution and tumor uptake, and the requirements to develop an optimal surface chemistry.

Design and synthesis of gold nanostars-based SERS nanotags for bioimaging applications

Surface-enhanced Raman spectroscopy (SERS) nanotags hold a unique place among bioimaging contrast agents due to their fingerprint-like spectra, which provide one of the highest degrees of detection specificity. However, in order to achieve a sufficiently high signal intensity, targeting capabilities, and biocompatibility, all components of nanotags must be rationally designed and tailored to a specific application. Design parameters include fine-tuning the properties of the plasmonic core as well as optimizing the choice of Raman reporter molecule, surface coating, and targeting moieties for the intended application. This review introduces readers to the principles of SERS nanotag design and discusses both established and emerging protocols of their synthesis, with a specific focus on the construction of SERS nanotags in the context of bioimaging and theranostics.

Recent Advances in Photosensitizers as Multifunctional Theranostic Agents for Imaging-Guided Photodynamic Therapy of Cancer

In recent years tremendous effort has been invested in the field of cancer diagnosis and treatment with an overall goal of improving cancer management, therapeutic outcome, patient survival, and quality of life. Photodynamic Therapy (PDT), which works on the principle of light-induced activation of photosensitizers (PS) leading to Reactive Oxygen Species (ROS) mediated cancer cell killing has received increased attention as a promising alternative to overcome several limitations of conventional cancer therapies. Compared to conventional therapies, PDT offers the advantages of selectivity, minimal invasiveness, localized treatment, and spatio-temporal control which minimizes the overall therapeutic side effects and can be repeated as needed without interfering with other treatments and inducing treatment resistance. Overall PDT efficacy requires proper planning of various parameters like localization and concentration of PS at the tumor site, light dose, oxygen concentration and heterogeneity of the tumor microenvironment, which can be achieved with advanced imaging techniques. Consequently, there has been tremendous interest in the rationale design of PS formulations to exploit their theranostic potential to unleash the imperative contribution of medical imaging in the context of successful PDT outcomes. Further, recent advances in PS formulations as activatable phototheranostic agents have shown promising potential for finely controlled imaging-guided PDT due to their propensity to specifically turning on diagnostic signals simultaneously with photodynamic effects in response to the tumor-specific stimuli. In this review, we have summarized the recent progress in the development of PS-based multifunctional theranostic agents for biomedical applications in multimodal imaging combined with PDT. We also present the role of different imaging modalities; magnetic resonance, optical, nuclear, acoustic, and photoacoustic in improving the pre-and post-PDT effects. We anticipate that the information presented in this review will encourage future development and design of PSs for improved image-guided PDT for cancer treatment.

Metalloporphyrins in Medicine: From History to Recent Trends

The history of metalloporphyrins dates back more than 200 years ago. Metalloporphyrins are excellent catalysts, capable of forming supramolecular systems, participate in oxygen photosynthesis, transport, and used as contrast agents or superoxide dismutase mimetics. Today, metalloporphyrins represent complexes of conjugated π-electron system and metals from the entire periodic system. However, the effect of these compounds on living systems has not been fully understood, and researchers are exploring the properties of metalloporphyrins thereby extending their further application. This review provides an overview of the variety of metalloporphyrins that are currently used in different medicine fields and how metalloporphyrins became the subject of scientists' interest. Currently, metalloporphyrins utilization has expanded significantly, which gave us an opprotunuty to summarize recent progress in metalloporphyrins derivatives and prospects of their application in the treatment and diagnosis of different diseases.

Current trends in pyrrole and porphyrin-derived nanoscale materials for biomedical applications

This article is written to provide an up-to-date review of pyrrole-based biomedical materials. Porphyrins and other tetrapyrrolic molecules possess unique magnetic, optical and other photophysical properties that make them useful for bioimaging and therapy. This review touches briefly on some of the synthetic strategies to obtain porphyrin- and tetrapyrrole-based nanoparticles, as well as the variety of applications in which crosslinked, self-assembled, porphyrin-coated and other nanoparticles are utilized. We explore examples of these nanoparticles' applications in photothermal therapy, drug delivery, photodynamic therapy, stimuli response, fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, computed tomography and positron emission tomography. We anticipate that this review will provide a comprehensive summary of pyrrole-derived nanoparticles and provide a guideline for their further development.

State of the Art Biocompatible Gold Nanoparticles for Cancer Theragnosis

Research on cancer theragnosis with gold nanoparticles (AuNPs) has rapidly increased, as AuNPs have many useful characteristics for various biomedical applications, such as biocompatibility, tunable optical properties, enhanced permeability and retention (EPR), localized surface plasmon resonance (LSPR), photothermal properties, and surface enhanced Raman scattering (SERS). AuNPs have been widely utilized in cancer theragnosis, including phototherapy and photoimaging, owing to their enhanced solubility, stability, biofunctionality, cancer targetability, and biocompatibility. In this review, specific characteristics and recent modifications of AuNPs over the past decade are discussed, as well as their application in cancer theragnostics and future perspectives. In the future, AuNP-based cancer theragnosis is expected to facilitate the development of innovative and novel strategies for cancer therapy.

Two-way magnetic resonance tuning and enhanced subtraction imaging for non-invasive and quantitative biological imaging

Distance-dependent magnetic resonance tuning (MRET) technology enables the sensing and quantitative imaging of biological targets in vivo, with the advantage of deep tissue penetration and fewer interactions with the surroundings as compared with those of fluorescence-based Förster resonance energy transfer. However, applications of MRET technology in vivo are currently limited by the moderate contrast enhancement and stability of T1-based MRET probes. Here we report a new two-way magnetic resonance tuning (TMRET) nanoprobe with dually activatable T1 and T2 magnetic resonance signals that is coupled with dual-contrast enhanced subtraction imaging. This integrated platform achieves a substantially improved contrast enhancement with minimal background signal and can be used to quantitatively image molecular targets in tumours and to sensitively detect very small intracranial brain tumours in patient-derived xenograft models. The high tumour-to-normal tissue ratio offered by TMRET in combination with dual-contrast enhanced subtraction imaging provides new opportunities for molecular diagnostics and image-guided biomedical applications.

Present and Future of Surface-Enhanced Raman Scattering

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

Electron Compensation Effect Suppressed Silver Ion Release and Contributed Safety of Au@Ag Core-Shell Nanoparticles

Silver nanoparticles (Ag NPs) have promising plasmonic properties, however, they are rarely used in biomedical applications because of their potent toxicity. Herein, an electron compensation effect from Au to Ag was applied to design safe Au@Ag core-shell NPs. The Ag shell thickness was precisely regulated to enable the most efficient electron enrichment in Ag shell of Au@Ag_2.4 NPs, preventing Ag oxidation and subsequent Ag⁺ ion release. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure analysis revealed the electron transfer process from Au core to Ag shell, and inductively coupled plasma optical emission spectroscopy analysis confirmed the low Ag⁺ ion release from Au@Ag_2.4 NPs. Bare Au@Ag_2.4 NPs showed much lower toxicological responses than Ag NPs in BEAS-2B and Raw 264.7 cells and acute lung inflammation mouse models, and PEGylation of Au@Ag_2.4 NPs could further improve their safety to L02 and HEK293T cells as well as mice through intravenous injection. Further, diethylthiatri carbocyanine iodide attached pAu@Ag_2.4 NPs exhibited intense surface-enhanced Raman scattering signals and were used for Raman imaging of MCF7 cells and Raman biosensing in MCF7 tumor-bearing mice. This electron compensation effect opens up new opportunity for broadening biomedical application of Ag-based NPs.

Dual-Mode Dark Field and Surface-Enhanced Raman Scattering Liposomes for Lymphoma and Leukemia Cell Imaging

Multifunctional probes are needed to characterize individual cells simultaneously by different techniques to provide complementary information. A preparative method and an in vitro demonstration of function are presented for a dual-function dark field microscopy/surface-enhanced Raman scattering (SERS) liposome probe for cancer. Liposomes composed of zwitterionic lipids are valuable both to limit biofouling and to serve as a modular matrix to incorporate a variety of functional molecules and hence are used here as vehicles for SERS-active materials. Dark field microscopy and SERS represent new combined functionalities for targeted liposomal probes. Two methods of antibody conjugation to SERS liposomes are demonstrated: (i) direct conjugation to functional groups on the SERS liposome surface and (ii) postinsertion of lipid-functionalized antibody fragments (Fabs) into preformed SERS liposomes. In vitro experiments targeting both lymphoma cell line LY10 and primary human chronic lymphocytic leukemia (CLL) cells demonstrate the usefulness of these probes as optical contrast agents in both dark field and Raman microscopy.

Metalloporphyrin Nanoparticles: Coordinating Diverse Theranostic Functions

Metalloporphyrins serve key roles in natural biological processes and also have demonstrated utility for biomedical applications. They can be encapsulated or grafted in conventional nanoparticles or can self-assemble themselves at the nanoscale. A wide range of metals can be stably chelated either before or after porphyrin nanoparticle formation, without the necessity of any additional chelator chemistry. The addition of metals can substantially alter a range of behaviors such as modulating phototherapeutic efficacy; conferring responsiveness to biological stimuli; or providing contrast for magnetic resonance, positron emission or surface enhanced Raman imaging. Chelated metals can also provide a convenient handle for bioconjugation with other molecules via axial coordination. This review provides an overview of some recent biomedical, nanoparticulate approaches involving gain-of-function metalloporphyrins and related molecules.

Trojan Horse nanotheranostics with dual transformability and multifunctionality for highly effective cancer treatment

Nanotheranostics with integrated diagnostic and therapeutic functions show exciting potentials towards precision nanomedicine. However, targeted delivery of nanotheranostics is hindered by several biological barriers. Here, we report the development of a dual size/charge- transformable, Trojan-Horse nanoparticle (pPhD NP) for delivery of ultra-small, full active pharmaceutical ingredients (API) nanotheranostics with integrated dual-modal imaging and trimodal therapeutic functions. pPhD NPs exhibit ideal size and charge for drug transportation. In tumour microenvironment, pPhD NPs responsively transform to full API nanotheranostics with ultra-small size and higher surface charge, which dramatically facilitate the tumour penetration and cell internalisation. pPhD NPs enable visualisation of biodistribution by near-infrared fluorescence imaging, tumour accumulation and therapeutic effect by magnetic resonance imaging. Moreover, the synergistic photothermal-, photodynamic- and chemo-therapies achieve a 100% complete cure rate on both subcutaneous and orthotopic oral cancer models. This nanoplatform with powerful delivery efficiency and versatile theranostic functions shows enormous potentials to improve cancer treatment.

Size and charge can significantly affect delivery of therapeutic agents to tumours. Here, the authors report on nanoparticles optimised for delivery to the tumour which release smaller particles and change charge in the tumour microenvironment to optimise tumour penetration and cellular uptake.

Lipid Bilayer-Enabled Synthesis of Waxberry-like Core-Fluidic Satellite Nanoparticles: Toward Ultrasensitive Surface-Enhanced Raman Scattering Tags for Bioimaging

Herein, we presented waxberry-like core-satellite (C-S) nanoparticles (NPs) prepared by an in situ growth of satellite gold NPs on spherical phospholipid bilayer-coated gold cores. The fluidic lipid bilayer cross-linker was reported for the first time, which imparted several novel morphological and optical properties to the C-S NPs. First, it regulated the anisotropic growth of the satellite NPs into vertically oriented nanorods on the core NP surface. Thus, an interesting waxberry-like nanostructure could be obtained, which was different from the conventional raspberry-like C-S structures decorated with spherical satellite NPs. Second, the satellite NPs were "soft-landed" on the lipid bilayer and could move on the core NP surface under certain conditions. The movement induced tunable plasmonic features in the C-S NPs. Furthermore, the fluidic lipid bilayer was capable of not only holding an abundance of reporter molecules but also delivering them to the hotspots at the junctions between the core and satellite NPs, which made the C-S NPs an excellent candidate for preparing ultrasensitive surface-enhanced Raman scattering (SERS) tags. The bioimaging capabilities of the C-S NP-based SERS tags were successfully demonstrated in living cells and mice. The developed SERS tags hold great potential for bioanalysis and medical diagnostics.

Self-indicating, fully active pharmaceutical ingredients nanoparticles (FAPIN) for multimodal imaging guided trimodality cancer therapy

Conventional drug delivery systems contain substantial amounts of excipients such as polymers and lipids, typically with low drug loading capacity and lack of intrinsic traceability and multifunctionality. Here, we report fully active pharmaceutical ingredient nanoparticles (FAPIN) which were self-assembled by minimal materials, but seamlessly orchestrated versatile theranostic functionalities including: i) self-delivery: no additional carriers were required, all components in the formulation are active pharmaceutical ingredients; ii) self-indicating: no additional imaging tags were needed. The nanoparticle itself was composed of 100% imaging agents, so that the stability, drug release, subcellular dispositions, biodistribution and therapeutic efficacy of FAPINs can be readily visualized by ample imaging capacities, including energy transfer relay dominated, dual-color fluorogenic property, near-infrared fluorescence imaging and magnetic resonance imaging; and iii) highly effective trimodality cancer therapy, encompassing photodynamic-, photothermal- and chemo-therapies. FAPINs were fabricated with very simple material (a photosensitizer-drug conjugate), unusually achieved ∼10 times better in vitro antitumor activity than their free counterparts, and were remarkably efficacious in patient-derived xenograft (PDX) glioblastoma multiforme animal models. Only two doses of FAPINs enabled complete ablation of highly-malignant PDX tumors in 50% of the mice.

Advanced Functional Nanomaterials for Theranostics

Nanoscale materials have been explored extensively as agents for therapeutic and diagnostic (i.e. theranostic) applications. Research efforts have shifted from exploring new materials in vitro to designing materials that function in more relevant animal disease models, thereby increasing potential for clinical translation. Current interests include non-invasive imaging of diseases, biomarkers and targeted delivery of therapeutic drugs. Here, we discuss some general design considerations of advanced theranostic materials and challenges of their use, from both diagnostic and therapeutic perspectives. Common classes of nanoscale biomaterials, including magnetic nanoparticles, quantum dots, upconversion nanoparticles, mesoporous silica nanoparticles, carbon-based nanoparticles and organic dye-based nanoparticles, have demonstrated potential for both diagnosis and therapy. Variations such as size control and surface modifications can modulate biocompatibility and interactions with target tissues. The needs for improved disease detection and enhanced chemotherapeutic treatments, together with realistic considerations for clinically translatable nanomaterials will be key driving factors for theranostic agent research in the near future.

Assembly of BODIPY-carbazole dyes with liposomes to fabricate fluorescent nanoparticles for lysosomal bioimaging in living cells

A strategy was developed to change an ACQ organic dye into a fluorescent nanoparticle probe for lysosomal bioimaging.

Rethinking translational nanomedicine: insights from the 'bottom-up' design of the Porphysome for guiding the clinical development of imageable nanomaterials

Progress in therapeutics and biotechnologies leveraging new insights in our understanding of cancer biology and progression have had an underwhelming clinical significance thus far. A key challenge arising from the creation of nanomedicines consolidating multiple desirable functionalities into a 'all-in-one' platform is that the layering of functionalities into a single agent introduces novel complexities that significantly impede clinical translation. An alternative design approach seeks to exploit intrinsically multi-functional building block to assemble nanomedicines from the bottom-up, yielding agents with a multiplicity of radiologic, pharmacologic, and therapeutic properties derived from a single constituent. Herein are highlighted recent developments in the formulation, multi-modal imaging, and targeting of an exemplary 'one-for-all' nanomaterial-the Pyropheophorbide Porphysome-treated from a hitherto unexplored clinical design and development perspective.

Phospholipid Encapsulated AuNR@Ag/Au Nanosphere SERS Tags with Environmental Stimulus Responsive Signal Property

Surface-enhanced Raman scattering (SERS) tags draw much attention due to the ultrasensitivity and multiplex labeling capability. Recently, a new kind of SERS tags was rationally designed by encapsulating metal nanoparticles with phospholipid bilayers, showing great potential in theranostics. The lipid bilayer coating confers biocompatibility and versatility to changing surface chemistry of the tag; however, its "soft" feature may influence SERS signal stability, which is rarely investigated. Herein, we prepared phospholipid-coated AuNR@Ag/Au nanosphere SERS tags by using three different kinds of Raman reporters, i.e., thio-containing 4-nitrothiophenol (NT), nitrogen-containing hydrophobic chromophore cyanine 7 monoacid (Cy7), and alkyl chain-chromophore conjugate 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine (DiD). It was found that signal responses were different upon additional stimulation which the tags may encounter in theranostic applications including the presence of detergent Triton X-100, lipid membrane, and photothermal treatment. Living-cell imaging also showed signal changing distinction. The different SERS signal performances were attributed to the different Raman reporter releasing behaviors from the tags. This work revealed that Raman reporter structure determined signal stability of lipid-coated SERS tags, providing guidance for the design of stimulus responsive tags. Moreover, it also implied the potential of SERS technique for real time drug release study of lipid based nanomedicine.

Photosensitizing nanoparticles and the modulation of ROS generation

The association of PhotoSensitizer (PS) molecules with nanoparticles (NPs) forming photosensitizing NPs, has emerged as a therapeutic strategy to improve PS tumor targeting, to protect PS from deactivation reactions and to enhance both PS solubility and circulation time. Since association with NPs usually alters PS photophysical and photochemical properties, photosensitizing NPs are an important tool to modulate ROS generation. Depending on the design of the photosensitizing NP, i.e., type of PS, the NP material and the method applied for the construction of the photosensitizing NP, the deactivation routes of the excited state can be controlled, allowing the generation of either singlet oxygen or other reactive oxygen species (ROS). Controlling the type of generated ROS is desirable not only in biomedical applications, as in Photodynamic Therapy where the type of ROS affects therapeutic efficiency, but also in other technological relevant fields like energy conversion, where the electron and energy transfer processes are necessary to increase the efficiency of photoconversion cells. The current review highlights some of the recent developments in the design of Photosensitizing NPs aimed at modulating the primary photochemical events after light absorption.

Anionic Lipid, pH-Sensitive Liposome-Gold Nanoparticle Hybrids for Gene Delivery - Quantitative Research of the Mechanism

Gene therapy is a potential method for treating a large range of diseases. Gene vectors are widely used in gene therapy for promoting the gene delivery efficiency to the target cells. Here, gold nanoparticles (AuNPs) coated with dimethyldioctadecylammonium bromide (DODAB)/dioleoylphosphatidylethanolamine (DOPE) are synthesized using a facile method for a new gene vector (DODAB/DOPE-AuNPs), which possess 3- and 1.5-fold higher transfection efficiency than those of DODAB-AuNPs and a commercial transfection agent, respectively. Meanwhile, it is nontoxic with concentrations required for effective gene delivery. Imaging and quantification studies of cellular uptake reveal that DOPE increases gene copies in cells, which may be attributed to the smaller size of AuNPs/DNA complexes. The dissociation efficiency of DNA from the endocytic pathway is quantified by incubating with different buffers and investigated directly in the cells. The results suggest that DOPE increases the internalization of AuNPs/DNA complexes and promotes DNA release from early endosomes for the vector is sensitive to the anionic lipid membrane and the decreasing pH along the endocytic pathway. The new vector contains the potential to be the new alternative as gene delivery vector for biomedical applications.

Hybrid nanostructures for SERS: materials development and chemical detection

This review focuses on recent developments in hybrid and nanostructured substrates for SERS (surface-enhanced Raman scattering) studies. Thus substrates composed of at least two distinct types of materials, in which one is a SERS active metal, are considered here aiming at their use as platforms for chemical detection in a variety of contexts. Fundamental aspects related to the SERS effect and plasmonic behaviour of nanometals are briefly introduced. The materials described include polymer nanocomposites containing metal nanoparticles and coupled inorganic nanophases. Chemical approaches to tailor the morphological features of these substrates in order to get high SERS activity are reviewed. Finally, some perspectives for practical applications in the context of chemical detection of analytes using such hybrid platforms are presented.

Emerging applications of porphyrins in photomedicine

Biomedical applications of porphyrins and related molecules have been extensively pursued in the context of photodynamic therapy. Recent advances in nanoscale engineering have opened the door for new ways that porphyrins stand to potentially benefit human health. Metalloporphyrins are inherently suitable for many types of medical imaging and therapy. Traditional nanocarriers such as liposomes, dendrimers and silica nanoparticles have been explored for photosensitizer delivery. Concurrently, entirely new classes of porphyrin nanostructures are being developed, such as smart materials that are activated by specific biochemicals encountered at disease sites. Techniques have been developed that improve treatments by combining biomaterials with photosensitizers and functional moieties such as peptides, DNA and antibodies. Compared to simpler structures, these more complex and functional designs can potentially decrease side effects and lead to safer and more efficient phototherapies. This review examines recent research on porphyrin-derived materials in multimodal imaging, drug delivery, bio-sensing, phototherapy and probe design, demonstrating their bright future for biomedical applications.

Hexamodal imaging with porphyrin-phospholipid-coated upconversion nanoparticles

Hexamodal imaging using simple nanoparticles is demonstrated. Porphyrin-phospholipids are used to coat upconversion nanoparticles in order to generate a new biocompatible material. The nanoparticles are characterized in vitro and in vivo for imaging via fluorescence, upconversion, positron emission tomography, computed tomography, Cerenkov luminescence, and photoacoustic tomography.

Nano-enabled SERS reporting photosensitizers

To impart effective cellular damage via photodynamic therapy (PDT), it is vital to deliver the appropriate light dose and photosensitizer concentration, and to monitor the PDT dose delivered at the site of interest. In vivo monitoring of photosensitizers has in large part relied on their fluorescence emission. Palladium-containing photosensitizers have shown promising clinical results by demonstrating near full conversion of light to PDT activity at the cost of having undetectable fluorescence. We demonstrate that, through the coupling of plasmonic nanoparticles with palladium-photosensitizers, surface-enhanced Raman scattering (SERS) provides both reporting and monitoring capability to otherwise quiescent molecules. Nano-enabled SERS reporting of photosensitizers allows for the decoupling of the therapeutic and imaging mechanisms so that both phenomena can be optimized independently. Most importantly, the design enables the use of the same laser wavelength to stimulate both the PDT and imaging features, opening the potential for real-time dosimetry of photosensitizer concentration and PDT dose delivery by SERS monitoring.

Characterization of phospholipid-encapsulated gold nanoparticles: a versatile platform to study drug delivery and cellular uptake mechanisms

The data presented in this work aim to provide a comprehensive characterization of lipid-coated gold nanoparticles. We show that it is possible to envelop gold nanoparticles with a coating of lipids during the formation of the gold nanoparticles, that the gold in these lipid-coated gold nanoparticles is crystalline and the size and shape can be controlled by the reaction conditions (within limits), that the lipid coating corresponds to a thickness consistent with the formation of a bilayer, that the bilayer can include fluorescent probes that, while quenched, can be used to trace the fate of the gold nanoparticles in cellular systems, that their surface charge, and hence their overall stability in solution, is influenced by the lipid coating, and that while some lipid dyes may exchange among the particles, they are sufficiently stable to exchange to permit their use as tracers in cell studies. We believe this is the most comprehensive characterization of these systems to date.

Rational design for the controlled aggregation of gold nanorods via phospholipid encapsulation for enhanced Raman scattering

This study describes a procedure that found a balance between the ability of polymer-stabilized nanorods (NRs) to self-assemble and the creation of narrow gaps to make reproducibly bright surface-enhanced Raman scattering (SERS) nanorod dimers. NRs were end-functionalized with polymers, which enabled end-to-end self-assembly of NR chains and control over inter-rod separation through polymer molecular weight (MW). We found a way to quench the self-assembly, by phospholipid encapsulation, reducing the polydispersity of the aggregates while rendering them water-soluble. This reduction in polydispersity and preferential isolation of short-chain nanorod species is important for maximizing SERS enhancement from nanorod chains. We prepared NR aggregates that exhibit ∼5-50 times greater SERS intensity than isolated rods (and ∼750× greater than bare dye) depending on inter-rod separation, when using Oxazine 725 reporter molecules. Colloidal stability of NR aggregates and temporal stability of the SERS signal in water were observed for 110 days. With enhanced SERS intensity, water solubility, and stability, these NR aggregates are promising optical probes for future biological applications.

Gold nanoparticle supported phospholipid membranes as a biomimetic biosensor platform for phosphoinositide signaling detection

Enzyme mediated phosphoinositide signaling plays important regulatory roles in diverse cellular processes and has close implication in human diseases. However, detection of phosphoinositide enzymes remains a challenge because of the difficulty in discriminating the phosphorylation patterns of phosphoinositide. Here we develop a novel enzyme-activated gold nanoparticles (AuNPs) assembly strategy as a homogeneous colorimetric biosensor for activity detection of phosphoinositide kinases and phosphatases. This strategy utilizes a biomimetic mechanism of phosphoinositide signaling, in which AuNP supported phospholipid membranes are constructed to mimic the cellular membrane substrate, and AuNPs modified with the pleckstrin homology (PH) domain of cytosolic proteins are designed for specific, multivalent recognition of phosphorylated phosphoinositides. This biomimetic strategy enables efficient enzymatic reactions of the substrate and highly selective detection of target enzyme. The biosensor is demonstrated for the detection of phosphoinositide 3-kinase (PI3K) and phosphatase with tensin homology (PTEN). The results revealed that it allows sensitive, rapid visual detection of the enzymes with pM detection limits and four-decade wide dynamic ranges, and is capable of detecting enzyme activities in complex cell lysate samples. This biosensor might provide a general biosensor platform for high-throughput detection of phosphoinositide enzymes with high sensitivity and selectivity in biomedical research and clinical diagnostics.

Aggregate enhanced trimodal porphyrin shell microbubbles for ultrasound, photoacoustic, and fluorescence imaging

Microbubbles (MBs) are currently used as ultrasound (US) contrast agents and as delivery vehicles for site-specific US-triggered drug and gene delivery. Multimodal US-based imaging methods have been applied preclinically to assess and validate the effectiveness and fate of MBs in imaging and therapy. Here we present the first intrinsically trimodal MBs by incorporating a dense concentration of porphyrin molecules within a MB shell, enabled by the use of a single porphyrin-lipid component. These MBs possess US, photoacoustic, and fluorescence properties that are demonstrated in solution and in a mouse tumor xenograft model. They also have potential to be extended to other imaging modalities such as magnetic resonance imaging and nuclear imaging.

Surface-chemistry effect on cellular response of luminescent plasmonic silver nanoparticles

Cellular response of inorganic nanoparticles (NPs) is strongly dependent on their surface chemistry. By taking advantage of robust single-particle fluorescence and giant Raman enhancements of unique polycrystalline silver NPs (AgNPs), we quantitatively investigated effects of two well-known surface chemistries, passive PEGylation and active c-RGD peptide conjugation, on in vitro behaviors of AgNPs at high temporal and spatial resolution as well as chemical level using fluorescence and Raman microscopy. The results show that specific c-RGD peptide−α_vβ₃ integrin interactions not only induced endosome formation more rapidly, enhanced constrained diffusion, but also minimized nonspecific chemical interactions between the NPs and intracellular biomolecules than passive PEGylation chemistry; as a result, surface enhanced Raman scattering (SERS) signals of c-RGD peptides were well resolved inside endosomes in the live cells, while Raman signals of PEGylated AgNPs remained unresolvable due to interference of surrounding biomolecules, opening up an opportunity to investigate specific ligand–receptor interactions in real time at the chemical level.

Surface morphology and optical properties of porphyrin/Au and Au/porphyrin/Au systems

Porphyrin/Au and Au/porphyrin/Au systems were prepared by vacuum evaporation and vacuum sputtering onto glass substrate. The surface morphology of as-prepared systems and those subjected to annealing at 160°C was studied by optical microscopy, atomic force microscopy, and scanning electron microscopy techniques. Absorption and luminescence spectra of as-prepared and annealed samples were measured. Annealing leads to disintegration of the initially continuous gold layer and formation of gold nanoclusters. An amplification of Soret band magnitude was observed on the Au/meso-tetraphenyl porphyrin (TPP) system in comparison with mere TPP. Additional enhancement of luminescence was observed after the sample annealing. In the case of sandwich Au/porphyrin/Au structure, suppression of one of the two porphyrins' luminescence maxima and sufficient enhancement of the second one were observed.

Engineering multifunctional nanoparticles: all-in-one versus one-for-all

Multifunctional nanoparticles have been developed to overcome the conventional hurdles associated with the diagnosis and treatment of disease. However, there are often caveats involved with the development and clinical translation of multifunctional nanoparticles largely regarding the notion that additional functionality increases nanoparticle complexity. Here, we discuss two design concepts, a conventional approach, 'all-in-one', and introduce the concept of 'one-for-all' to suggest that multifunctionality does not necessarily result in multicomponent complex nanoparticles. This review focuses on the design concepts of all-in-one and one-for-all with examples of each approach and a discussion on the implications for clinical translation.