Polymeric lipid assemblies as novel theranostic tools

Multifunctional Carbon-Based Nanoparticles: Theranostic Applications in Cancer Therapy and Diagnosis

Cancer diagnosis and treatment are the most critical challenges in modern medicine. Conventional cancer treatments no longer meet the needs of the health field due to the high rate of mutations and epigenetic factors that have caused drug resistance in tumor cells. Hence, the search for unique methods and factors is quickly expanding. The development of nanotechnology in medicine and the search for a system to integrate treatment and diagnosis to achieve an effective approach to overcome the known limitations of conventional treatment methods have led to the emergence of theranostic nanoparticles and nanosystems based on these nanoparticles. An influential group of these nanoparticles is carbon-based theranostic nanoparticles. These nanoparticles have received significant attention due to their unique properties, such as electrical conductivity, high strength, excellent surface chemistry, and wide range of structural diversity (graphene, nanodiamond, carbon quantum dots, fullerenes, carbon nanotubes, and carbon nanohorns). These nanoparticles were widely used in various fields, such as tissue engineering, drug delivery, imaging, and biosensors. In this review, we discuss in detail the recent features and advances in carbon-based theranostic nanoparticles and the advanced and diverse strategies used to treat diseases with these nanoparticles.

Submicron-Sized In Situ Osmotic Pressure Sensors for In Vitro Applications in Biology

Physical forces are important cues in determining the development and the normal function of biological tissues. While forces generated by molecular motors have been widely studied, forces resulting from osmotic gradients have been less considered in this context. A possible reason is the lack of direct in situ measurement methods that can be applied to cell and organ culture systems. Herein, novel kinds of resonance energy transfer (FRET)-based liposomal sensors are developed, so that their sensing range and sensitivity can be adjusted to satisfy physiological osmotic conditions. Several types of sensors are prepared, either based on polyethylene glycol- (PEG)ylated liposomes with steric stabilization and stealth property or on crosslinked liposomes capable of enduring relatively harsh environments for liposomes (e.g., in the presence of biosurfactants). The sensors are demonstrated to be effective in the measurement of osmotic pressures in pre-osteoblastic in vitro cell culture systems by means of FRET microscopy. This development paves the way toward the in situ sensing of osmotic pressures in biological culture systems.

Modeling Polyzwitterion-Based Drug Delivery Platforms: A Perspective of the Current State-of-the-Art and Beyond

Drug delivery platforms are anticipated to have biocompatible and bioinert surfaces. PEGylation of drug carriers is the most approved method since it improves water solubility and colloid stability and decreases the drug vehicles’ interactions with blood components. Although this approach extends their biocompatibility, biorecognition mechanisms prevent them from biodistribution and thus efficient drug transfer. Recent studies have shown (poly)zwitterions to be alternatives for PEG with superior biocompatibility. (Poly)zwitterions are super hydrophilic, mainly stimuli-responsive, easy to functionalize and they display an extremely low protein adsorption and long biodistribution time. These unique characteristics make them already promising candidates as drug delivery carriers. Furthermore, since they have highly dense charged groups with opposite signs, (poly)zwitterions are intensely hydrated under physiological conditions. This exceptional hydration potential makes them ideal for the design of therapeutic vehicles with antifouling capability, i.e., preventing undesired sorption of biologics from the human body in the drug delivery vehicle. Therefore, (poly)zwitterionic materials have been broadly applied in stimuli-responsive “intelligent” drug delivery systems as well as tumor-targeting carriers because of their excellent biocompatibility, low cytotoxicity, insignificant immunogenicity, high stability, and long circulation time. To tailor (poly)zwitterionic drug vehicles, an interpretation of the structural and stimuli-responsive behavior of this type of polymer is essential. To this end, a direct study of molecular-level interactions, orientations, configurations, and physicochemical properties of (poly)zwitterions is required, which can be achieved via molecular modeling, which has become an influential tool for discovering new materials and understanding diverse material phenomena. As the essential bridge between science and engineering, molecular simulations enable the fundamental understanding of the encapsulation and release behavior of intelligent drug-loaded (poly)zwitterion nanoparticles and can help us to systematically design their next generations. When combined with experiments, modeling can make quantitative predictions. This perspective article aims to illustrate key recent developments in (poly)zwitterion-based drug delivery systems. We summarize how to use predictive multiscale molecular modeling techniques to successfully boost the development of intelligent multifunctional (poly)zwitterions-based systems.

Sulfobetaine Methacrylate Polymers of Unconventional Polyzwitterion Architecture and Their Antifouling Properties

Combining high hydrophilicity with charge neutrality, polyzwitterions are intensely explored for their high biocompatibility and low-fouling properties. Recent reports indicated that in addition to charge neutrality, the zwitterion's segmental dipole orientation is an important factor for interacting with the environment. Accordingly, a series of polysulfobetaines with a novel architecture was designed, in which the cationic and anionic groups of the zwitterionic moiety are placed at equal distances from the backbone. They were investigated by in vitro biofouling assays, covering proteins of different charges and model marine organisms. All polyzwitterion coatings reduced the fouling effectively compared to model polymer surfaces of poly(butyl methacrylate), with a nearly equally good performance as the reference polybetaine poly(3-(N-(2-(methacryloyloxy)ethyl)-N,N-dimethylammonio)propanesulfonate). The specific fouling resistance depended on the detailed chemical structure of the polyzwitterions. Still, while clearly affecting the performance, the precise dipole orientation of the sulfobetaine group in the polyzwitterions seems overall to be only of secondary importance for their antifouling behavior.

Photo-Functionalized Magnetic Nanoparticles as a Nanocarrier of Photodynamic Anticancer Agent for Biomedical Theragnostics

Various theragnostic agents have been devised and developed as cancer treatments; however, existing agents are often limited by their specific functions and complexities. Here, we report multifunctional magnetite (Fe₃O₄) nanoparticles functionalized with chlorin e6 (Ce6) and folic acid (FA) using a simple fabrication process to be used as theragnostic agents in photodynamic therapy (PDT). The effectiveness of cellular uptake of Fe3O4-Ce6-FA nanoparticles (FCF NPs) and its visualization as well as the photodynamic anticancer activities were evaluated. The mechanism of cancer cell death by the FCF NPs was also verified with qualitative and quantitative methods. Results indicate that FCF NPs have good penetration efficacy, resulting in excellent in vitro fluorescence and magnetic resonance imaging in cancer cells. FCF NPs exhibited promising anticancer activity in an irradiation time- and FCF NPs-dose-dependent manner in various cancer cell lines, leading to apoptotic cell death via morphological changes in cell membrane, nuclear, and DNA damage, and via overexpression of apoptosis-related genes, such as ZFP36L1, CYR61, GADD45G, caspases-2, -3, -9, 10, and -14. This study suggests that FCF NPs may be safely used in cancer therapy via PDT and could be a versatile therapeutic tool and biocompatible theragnostic agent, which may be used in diagnostic imaging.

Surface Modification by Polyzwitterions of the Sulfabetaine-Type, and Their Resistance to Biofouling

Films of zwitterionic polymers are increasingly explored for conferring fouling resistance to materials. Yet, the structural diversity of polyzwitterions is rather limited so far, and clear structure-property relationships are missing. Therefore, we synthesized a series of new polyzwitterions combining ammonium and sulfate groups in their betaine moieties, so-called poly(sulfabetaine)s. Their chemical structures were varied systematically, the monomers carrying methacrylate, methacrylamide, or styrene moieties as polymerizable groups. High molar mass homopolymers were obtained by free radical polymerization. Although their solubilities in most solvents were very low, brine and lower fluorinated alcohols were effective solvents in most cases. A set of sulfabetaine copolymers containing about 1 mol % (based on the repeat units) of reactive benzophenone methacrylate was prepared, spin-coated onto solid substrates, and photo-cured. The resistance of these films against the nonspecific adsorption by two model proteins (bovine serum albumin-BSA, fibrinogen) was explored, and directly compared with a set of references. The various polyzwitterions reduced protein adsorption strongly compared to films of poly(nbutyl methacrylate) that were used as a negative control. The poly(sulfabetaine)s showed generally even somewhat higher anti-fouling activity than their poly(sulfobetaine) analogues, though detailed efficacies depended on the individual polymer-protein pairs. Best samples approach the excellent performance of a poly(oligo(ethylene oxide) methacrylate) reference.

Functional Built-In Template Directed Siliceous Fluorescent Supramolecular Vesicles as Diagnostics

Functional template directed synthesis of hybrid siliceous fluorescent vesicle (HSFV) is fabricated by using fluorescent vesicle as a built-in template. The template vesicle is the ionic self-assembly of an aggregation-induced emission (AIE) fluorogen. Upon depositing folic acid modified silica shell on its surface, the obtained HSFVs display low cytotoxicity, significant fluorescence, and targeted drug delivery toward cancer cells. Furthermore, the wall-thickness of the HSFVs can be controlled via altered concentration of silica source. This is the first report of HSFV employing the template vesicle as a built-in fluorescent agent, which represents a good example of rational design for an effective diagnostics, and may open up a new avenue for precision medicine.

Can PEI microgels become biocompatible upon betainization?

Polyethylene imine (PEI) microgels prepared via micro emulsion polymerization technique were treated with 1,3-propane sultone to obtained betainized PEI (b-PEI) microgels. The betainization reaction generated zwitterions on PEI microgel that are positive charges from quarternized amine groups of PEI, and the newly formed negative charges from SO₃^- groups from the modifying agent, 1,3-propane sultone offered interesting properties. The smaller size of b-PEI microgels that are obtained by simple filtration were increased with betainization from 512±14 to 1114±86nm. Also, the betainization of PEI microgel provided negative zeta potential values at high pH values as 9, 10, 11, and 12. Moreover, the b-PEI microgels render more effective dye absorption capabilities for anionic or cationic organic dyes such as Methyl Orange (MO) and Methylene Blue (MB) separately with the significant increase dye adsorption capacity of 354±31 and 274±19mg/g respectively. Moreover, antibacterial properties of b-PEI microgels tested on the E. coli ATCC 8739 and S. aureus ATCC 6538 were diminished whereas bare PEI has low MIC and MBC values (strong antibacterial properties). Interestingly, the PEI microgels known for their strong antibacterial and toxic nature found to be biocompatible upon betainization reaction. The biocompatibility test were carried with WST-1 tests and double staining methods. The cytotoxicity, apoptotic and necrotic cell tests were shown that PEI microgels induce no cytotoxicity up to 400μg/mL whereas PEI microgels possessed 50% toxicity at this concentration, suggesting that b-PEI microgels become biocompatible upon betainization with, 3-propane sultone.

Cytocompatible and multifunctional polymeric nanoparticles for transportation of bioactive molecules into and within cells

Multifunctional polymeric nanoparticles are materials with great potential for a wide range of biomedical applications. For progression in this area of research, unfavorable interactions of these nanoparticles with proteins and cells must be avoided in biological environments, for example, through treatment of the nanoparticle surfaces. Construction of an artificial cell membrane structure based on polymers bearing the zwitterionic phosphorylcholine group can prevent biological reactions at the surface effectively. In addition, certain bioactive molecules can be immobilized on the surface of the polymer to generate enough affinity to capture target biomolecules. Furthermore, entrapment of inorganic nanoparticles inside polymeric matrices enhances the nanoparticle functionality significantly. This review summarizes the preparation and characterization of cytocompatible and multifunctional polymeric nanoparticles; it analyzes the efficiency of their fluorescence function, the nature of the artificial cell membrane structure, and their performance as in-cell devices; and finally, it evaluates both their chemical reactivity and effects in cells.

IR-780 Loaded Phospholipid Mimicking Homopolymeric Micelles for Near-IR Imaging and Photothermal Therapy of Pancreatic Cancer

IR-780 iodide, a near-infrared (near-IR) fluorescent dye, can be utilized as an effective theranostic agent for both imaging and photothermal therapy. However, its lipophilicity limits its further biomedical applications. Herein, we synthesized a phospholipid mimicking amphiphilic homopolymer poly(12-(methacryloyloxy)dodecyl phosphorylcholine) (PMDPC) via reversible addition-fragmentation chain transfer (RAFT) polymerization. The amphiphilic homopolymer PMDPC can be self-assembled into micelles and used for the encapsulation of IR-780. The IR-780 loaded micelles (PMDPC-IR-780) exhibited low cytotoxicity in the dark, whereas remarkable photothermal cytotoxicity to pancreatic cancer cells (BxPC-3) was observed upon near-IR laser irradiation. We further investigated in vivo biodistribution of PMDPC-IR-780 micelles. Higher accumulation of PMDPC-IR-780 than that of free IR-780 in tumor tissue was verified, which might be ascribed to the enhanced permeability and retention (EPR) effect and long circulation time benefiting from the zwitterionic phosphorylcholine surface. Therefore, the IR-780 loaded phospholipid mimicking homopolymeric micelles could have great potential for cancer theranostics.

Photopolymerization of Dienoyl Lipids Creates Planar Supported Poly(lipid) Membranes with Retained Fluidity

Polymerization of substrate-supported bilayers composed of dienoylphosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability; however, the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl-phosphatidylcholine (mono-SorbPC), bis-dienoyl-phosphatidylcholine (bis-DenPC), and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lβ phase for each lipid. In all cases, polymerization reduced membrane fluidity; however, measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate interleaflet bonding. The D values measured after polymerization were 0.1-0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV-polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.

Combinatorial Approach to Nanoarchitectonics for Nonviral Delivery of Nucleic Acids

Nanoparticles based on cationic polymers, lipids or lipidoids are of great interest in the field of gene delivery applications. The research on these nanosystems is rapidly growing as they hold promise to treat wide variety of human diseases ranging from viral infections to genetic disorders and cancer. Recently, combinatorial design principles have been adopted for rapid generation of large numbers of chemically diverse polymers and lipids capable of forming multifunctional nanocarriers for the use in gene delivery applications. At the same time, current high-throughput screening systems as well as convenient cell assays and readout techniques allow for fast evaluation of cell transfection efficiencies and toxicities of libraries of novel gene delivery agents. This allows for a rapid evaluation of structure-function relationship as well as identification of novel efficient nanocarriers for cell transfection and gene therapy. Here, the recent contribution of high-throughput synthesis to the development of novel nanocarriers for gene delivery applications is described.

Facile synthesis of a multifunctional copolymer via a concurrent RAFT-enzymatic system for theranostic applications

Through a straightforward concurrent RAFT-enzymatic multicomponent polymerization system and subsequent post-polymerization modifications, a multi-functional copolymer for theranostic application has been efficiently prepared.

Pharmacokinetics, pharmacodynamics and toxicology of theranostic nanoparticles

Nanoparticles (NPs) are considered a promising tool in both diagnosis and therapeutics. Theranostic NPs possess the combined properties of targeted imaging and drug delivery within a single entity. While the categorization of theranostic NPs is based on their structure and composition, the pharmacokinetics of NPs are significantly influenced by the physicochemical properties of theranostic NPs as well as the routes of administration. Consequently, altered pharmacokinetics modify the pharmacodynamic efficacy and toxicity of NPs. Although theranostic NPs hold great promise in nanomedicine and biomedical applications, a lack of understanding persists on the mechanisms of the biodistribution and adverse effects of NPs. To better understand the diagnostic and therapeutic functions of NPs, this review discusses the factors that influence the pharmacokinetics, pharmacodynamics and toxicology of theranostic NPs, along with several strategies for developing novel diagnostic and therapeutic modalities.

Pleiotropic Role of Dietary Phytochemicals in Cancer: Emerging Perspectives for Combinational Therapy

Cancer is considered a complicated health issue worldwide. The mean cancer survival through standard therapeutic strategies has not been significantly improved over the past few decades. Hence, alternate remedies are needed to treat or prevent this dreadful disease being explored. Currently, it has been recognized that repeated treatment with chemotherapeutic agents has been largely ineffective due to multidrug resistance and further conventional treatment possesses limited drug accessibility to cancerous tissues, which in turn necessitates a higher dose resulting in increased cytotoxicity. Drug combinations have been practiced to address the problems associated with conventional single drug treatment. Recently, natural dietary agents have attracted much attention in cancer therapy because of their synergistic effects with anticancer drugs against different types of cancer. Natural phytochemicals may execute their anticancer activity through targeting diverse cancer cell signaling pathways, promoting cell cycle arrest and apoptosis, regulating antioxidant status and detoxification. This review focuses mainly on the anticancer efficacy of dietary phytochemicals in combination with standard therapeutic drugs reported from various in vitro and in vivo experimental studies apart from clinical trials. This review adds knowledge to the field of intervention studies using combinational modalities that opens a new window for cancer treatment/chemoprevention.

Co₉ Se₈ nanoplates as a new theranostic platform for photoacoustic/magnetic resonance dual-modal-imaging-guided chemo-photothermal combination therapy

A new theranostic platform is developed based on biocompatible poly(acrylic acid) (PAA)-Co9 Se8 nanoplates. These PAA-Co9 Se8 nanoplates are successfully utilized for photoacoustic imaging (PAI)/magnetic resonance imaging (MRI) dual-modal imaging. Moreover, the PAA-Co9 Se8 -DOX shows pH-responsive chemotherapy and enables the combination of photothermal therapy and chemotherapy to receive superior antitumor efficacy. This work promises further exploration of 2D nanoplatforms for theranostic applications.

Recent progress in designing shell cross-linked polymer capsules for drug delivery

This tutorial review highlights the progress made during recent years in the development of the shell cross-linked (SCL) polymer nanocapsules and the impact of the most important scientific ideas on this field of knowledge.

Theranostic nanoparticles

Theranostic nanoparticles hold the potential to revolutionize disease management. Over the last decade, there has been growing interest in the engineering of various kinds of theranostic nanoparticles for simultaneous cancer imaging and therapy in small animals. Efficient targeting of theranostic nanoparticles to the tumor site is critical for both diagnosis and therapy. However, difficulties still exist in the engineering of biocompatible theranostic nanoparticles with highly specific in vivo tumor-targeting capabilities. Here, we discuss the current and prospective status of theranostic nanoparticles that actively target tumors, as well as the challenges that still exist.

Tumor targeting, trifunctional dendritic wedge

We report in vitro and in vivo evaluation of a newly designed trifunctional theranostic agent for targeting solid tumors. This agent combines a dendritic wedge with high boron content for boron neutron capture therapy or boron MRI, a monomethine cyanine dye for visible-light fluorescent imaging, and an integrin ligand for efficient tumor targeting. We report photophysical properties of the new agent, its cellular uptake and in vitro targeting properties. Using live animal imaging and intravital microscopy (IVM) techniques, we observed a rapid accumulation of the agent and its retention for a prolonged period of time (up to 7 days) in fully established animal models of human melanoma and murine mammary adenocarcinoma. This macromolecular theranostic agent can be used for targeted delivery of high boron load into solid tumors for future applications in boron neutron capture therapy.

Phase segregation of polymerizable lipids to construct filters for separating lipid-membrane-embedded species

Supported lipid bilayer (SLB) platforms have been developed to transport and separate membrane-embedded species in the species' native bilayer environment. In this study, we used the phase segregation phenomenon of lipid mixtures containing a polymerizable diacetylene phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC), and a nonpolymerizable phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), to create filter barrier structures in SLBs. Upon exposing the phase segregated samples to UV light, the DiynePC-rich domains could become crosslinked and remain fixed on the surface of the support, while the DOPC-rich regions, where no crosslinking could happen, could be removed later by detergent washing, and thus became the void regions in the filter. During the filter fabrication process, we used the laminar flow configuration in a microfluidic channel to control the spatial locations of the feed region and filter region in the SLB. The flow in a microfluidic channel was also used to apply a strong hydrodynamic shear stress to the SLB to transport the membrane-embedded species from the feed region to the filter region. We varied the DiynePC/DOPC molar ratio from 60/40 to 80/20 to adjust the cutoff size of the filter barriers and used two model membrane-embedded species of different sizes to examine the filtering capability. One of the model species, Texas Red 1,2-dihexa-decanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (Texas Red DHPE), had a single-lipid size, and the other species, cholera toxin subunit B-GM1 complex, had a multilipid size. When the DiynePC/DOPC molar ratio was 60/40, both species had high penetration ratios in the filter region. However, when the ratio was increased to 70/30, only the Texas Red DHPE, which was the smaller of the two model species, could penetrate the filter to a considerable extent. When the ratio was increased to 80/20, neither of the model species could penetrate the filter region. The results showed the possibility of using phase segregation of a mixture containing a polymerizable lipid and a nonpolymerizable lipid to fabricate filter barrier structures with tunable cutoff sizes in SLBs.

Dendrimer-surfactant interactions

In this article, we reviewed the interactions between dendrimers and surfactants with particular focus on the interaction mechanisms and physicochemical properties of the yielding dendrimer-surfactant aggregates. In order to provide insight into the behavior of dendrimers in biological systems, the interactions of dendrimers with bio-surfactants such as phospholipids in bulk solutions, in solid-supported bilayers and at the interface of phases or solid-states were discussed. Applications of the dendrimer-surfactant aggregates as templates to guide the synthesis of nanoparticles and in drug or gene delivery were also mentioned.

Theranostic vesicles based on bovine serum albumin and poly(ethylene glycol)-block-poly(L-lactic-co-glycolic acid) for magnetic resonance imaging and anticancer drug delivery

Presented in this article is the preparation of a new theranostic vesicle which exhibits excellent in vitro and in vivo T1 magnetic resonance (MR) imaging contrast effect and good anticancer drug delivery ability. The theranostic vesicle has been easily prepared based on an amphiphilic biocompatible and biodegradable dibock copolymer, poly(ethylene glycol)-block-poly(l-lactic-co-glycolic acid) (PEG-b-PLGA) and bovine serum albumin-gadolinium (BSA-Gd) complexes. Dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-vis spectroscopy, and inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements confirmed the formation and physiological stability of BSA-Gd@PEG-b-PLGA vesicles. Furthermore, the in vitro and in vivo MR imaging experiments revealed their excellent T1-weighted MR imaging function. Red blood cell hemolysis and cytotoxicity experiments confirmed their good blood compatibility and low cytotoxicity. Doxorubicin (DOX) loading and release experiments indicated a more retarded release rate of DOX in those theranostic vesicles than sole PEG-b-PLGA nanoparticles without BSA. Overall, this new biocompatible and biodegradable vesicle shows promising potential in theranostic applications.

Creation of a polymer backbone in lipid bilayer membrane-based nanotubes for morphological and microenvironmental stabilization

We report a novel method for morphological and microenvironmental stabilization of single-walled bilayer nanotubes, which involves construction of a polymer backbone between the monolayers by intercalating a monomer, followed by in situ polymerization.

Phototriggerable liposomes: current research and future perspectives

The field of cancer nanomedicine is considered a promising area for improved delivery of bioactive molecules including drugs, pharmaceutical agents and nucleic acids. Among these, drug delivery technology has made discernible progress in recent years and the areas that warrant further focus and consideration towards technological developments have also been recognized. Development of viable methods for on-demand spatial and temporal release of entrapped drugs from the nanocarriers is an arena that is likely to enhance the clinical suitability of drug-loaded nanocarriers. One such approach, which utilizes light as the external stimulus to disrupt and/or destabilize drug-loaded nanoparticles, will be the discussion platform of this article. Although several phototriggerable nanocarriers are currently under development, I will limit this review to the phototriggerable liposomes that have demonstrated promise in the cell culture systems at least (but not the last). The topics covered in this review include (i) a brief summary of various phototriggerable nanocarriers; (ii) an overview of the application of liposomes to deliver payload of photosensitizers and associated technologies; (iii) the design considerations of photoactivable lipid molecules and the chemical considerations and mechanisms of phototriggering of liposomal lipids; (iv) limitations and future directions for in vivo, clinically viable triggered drug delivery approaches and potential novel photoactivation strategies will be discussed.

Steric-induced effects on stabilizing a lamellar structure

We investigate the behavior of multilamellar phases composed of lecithin and a commercial cosurfactant (Simusol), which is a mixture of ethoxylated fatty acids. Using X-ray scattering and a new procedure to fit the data, relevant parameters characterizing the lamellar structure were determined as a function of membrane composition, varying from 100% of lecithin to 100% of Simulsol. Scattering data illustrating the swelling of the lamellae for different amounts of cosurfactant are presented with the respective behavior of the Caillé parameter. With this experimental approach, we show that the incorporation of ethoxy brushes onto the lipid surface enhances repulsive interactions arising from membrane fluctuations and changes the interactions at the interface between bilayers.

Assessing the barriers to image-guided drug delivery

Imaging has become a cornerstone for medical diagnosis and the guidance of patient management. A new field called image-guided drug delivery (IGDD) now combines the vast potential of the radiological sciences with the delivery of treatment and promises to fulfill the vision of personalized medicine. Whether imaging is used to deliver focused energy to drug-laden particles for enhanced, local drug release around tumors, or it is invoked in the context of nanoparticle-based agents to quantify distinctive biomarkers that could risk stratify patients for improved targeted drug delivery efficiency, the overarching goal of IGDD is to use imaging to maximize effective therapy in diseased tissues and to minimize systemic drug exposure in order to reduce toxicities. Over the last several years, innumerable reports and reviews covering the gamut of IGDD technologies have been published, but inadequate attention has been directed toward identifying and addressing the barriers limiting clinical translation. In this consensus opinion, the opportunities and challenges impacting the clinical realization of IGDD-based personalized medicine were discussed as a panel and recommendations were proffered to accelerate the field forward.

Low-visibility light-intensity laser-triggered release of entrapped calcein from 1,2-bis (tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine liposomes is mediated through a type I photoactivation pathway

We recently reported on the physical characteristics of photo-triggerable liposomes containing dipalmitoylphosphatidylcholine (DPPC), and 1,2-bis (tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC(8,9)PC) carrying a photo agent as their payload. When exposed to a low-intensity 514 nm wavelength (continuous-wave) laser light, these liposomes were observed to release entrapped calcein green (Cal-G; Ex/Em 490/517 nm) but not calcein blue (Cal-B; Ex/Em 360/460 nm). In this study, we have investigated the mechanism for the 514 nm laser-triggered release of the Cal-G payload using several scavengers that are known specifically to inhibit either type I or type II photoreaction pathways. Liposomes containing DPPC:DC(8,9)PC: distearoylphosphatidylethanolamine (DSPE)-polyethylene glycol (PEG)-2000 (86:10:04 mole ratio) were loaded either with fluorescent (calcein) or nonfluorescent ((3)H-inulin) aqueous markers. In addition, a non-photo-triggerable formulation (1-palmitoyl-2-oleoyl phosphatidylcholine [POPC]:DC(8,9)PC:DSPE-PEG2000) was also studied with the same payloads. The 514 nm wavelength laser exposure on photo-triggerable liposomes resulted in the release of Cal-G but not that of Cal-B or (3)H-inulin, suggesting an involvement of a photoactivated state of Cal-G due to the 514 nm laser exposure. Upon 514 nm laser exposures, substantial hydrogen peroxide (H2O2, ≈100 μM) levels were detected from only the Cal-G loaded photo-triggerable liposomes but not from Cal-B-loaded liposomes (≤10 μM H2O2). The Cal-G release from photo-triggerable liposomes was found to be significantly inhibited by ascorbic acid (AA), resulting in a 70%-80% reduction in Cal-G release. The extent of AA-mediated inhibition of Cal-G release from the liposomes also correlated with the consumption of AA. No AA consumption was detected in the 514 nm laser-exposed Cal B-loaded liposomes, thus confirming a role of photoactivation of Cal-G in liposome destabilization. Inclusion of 100 mM K3Fe(CN)6 (a blocker of electron transfer) in the liposomes substantially inhibited Cal-G release, whereas inclusion of 10 mM sodium azide (a blocker of singlet oxygen of type II photoreaction) in the liposomes failed to block 514 nm laser-triggered Cal-G release. Taken together, we conclude that low-intensity 514 nm laser-triggered release of Cal-G from photo-triggerable liposomes involves the type I photoreaction pathway.

Mesoporous silica nanoparticles as antigen carriers and adjuvants for vaccine delivery

Vaccines have been at the forefront of improving human health for over two centuries. The challenges faced in developing effective vaccines flow from complexities associated with the immune system and requirement of an efficient and safe adjuvant to induce a strong adaptive immune response. Development of an efficient vaccine formulation requires careful selection of a potent antigen, efficient adjuvant and route of delivery. Adjuvants are immunological agents that activate the antigen presenting cells (APCs) and elicit a strong immune response. In the past decade, the use of mesoporous silica nanoparticles (MSNs) has gained significant attention as potential delivery vehicles for various biomolecules. In this review, we aim to highlight the potential of MSNs as vaccine delivery vehicles and their ability to act as adjuvants. We have provided an overview on the latest progress on synthesis, adsorption and release kinetics and biocompatibility of MSNs as next generation antigen carriers and adjuvants. A comprehensive summary on the ability of MSNs to deliver antigens and elicit both humoral and cellular immune responses is provided. Finally, we give insight on fundamental challenges and some future prospects of these nanoparticles as adjuvants.

Use of Nanotechnology to Develop Multi-Drug Inhibitors For Cancer Therapy

Therapeutic agents that inhibit a single target often cannot combat a multifactorial disease such as cancer. Thus, multi-target inhibitors (MTIs) are needed to circumvent complications such as the development of resistance. There are two predominant types of MTIs, (a) single drug inhibitor (SDIs) that affect multiple pathways simultaneously, and (b) combinatorial agents or multi-drug inhibitors (MDIs) that inhibit multiple pathways. Single agent multi-target kinase inhibitors are amongst the most prominent class of compounds belonging to the former, whereas the latter includes many different classes of combinatorial agents that have been used to achieve synergistic efficacy against cancer. Safe delivery and accumulation at the tumor site is of paramount importance for MTIs because inhibition of multiple key signaling pathways has the potential to lead to systemic toxicity. For this reason, the development of drug delivery mechanisms using nanotechnology is preferable in order to ensure that the MDIs accumulate in the tumor vasculature, thereby increasing efficacy and minimizing off-target and systemic side effects. This review will discuss how nanotechnology can be used for the development of MTIs for cancer therapy and also it concludes with a discussion of the future of nanoparticle-based MTIs as well as the continuing obstacles being faced during the development of these unique agents.’

Nanocarriers for tracking and treating diseases

Site directed drug delivery with high efficacy is the biggest challenge in the area of current pharmaceuticals. Biodegradable polymer-based controlled release nanoparticle platforms could be beneficial for targeted delivery of therapeutics and contrast agents for a myriad of important human diseases. Biodegradable nanoparticles, which can be engineered to load multiple drugs with varied physicochemical properties, contrast agents, and cellular or intracellular component targeting moieties, have emerged as potential alternatives for tracking and treating human diseases. In this review, we will highlight the current advances in the design and execution of such platforms for their potential application in the diagnosis and treatment of variety of diseases ranging from cancer to Alzheimer's and we will provide a critical analysis of the associated challenges for their possible clinical translation.

Tumor-targeting multi-functional nanoparticles for theragnosis: new paradigm for cancer therapy

Theragnostic nanoparticles (NPs) contain diagnostic and therapeutic functions in one integrated system, enabling diagnosis, therapy, and monitoring of therapeutic response at the same time. For diagnostic function, theragnostic NPs require the inclusion of noninvasive imaging modalities. Among them, optical imaging has various advantages including sensitivity, real-time and convenient use, and non-ionization safety, which make it the leading technique for theragnostic NPs. For therapeutic function, theragnostic NPs have been applied to chemotherapy, photodynamic therapy, siRNA therapy and photothermal therapy. In this review, we present a recent progress reported in the development and applications of theragnostic NPs for cancer therapy. More specifically, we will focus on theragnostic NPs related with optical imaging, highlighting promising strategies based on optical imaging techniques.

Paclitaxel-loaded iron platinum stealth immunomicelles are potent MRI imaging agents that prevent prostate cancer growth in a PSMA-dependent manner

Background and methods:

Problems with the clinical management of prostate cancer include the lack of both specific detection and efficient therapeutic intervention. We report the encapsulation of superparamagnetic iron platinum nanoparticles (SIPPs) and paclitaxel in a mixture of polyethyleneglycolated, fluorescent, and biotin-functionalized phospholipids to create multifunctional SIPP-PTX micelles (SPMs) that were conjugated to an antibody against prostate-specific membrane antigen (PSMA) for the specific targeting, magnetic resonance imaging (MRI), and treatment of human prostate cancer xenografts in mice.

Results:

SPMs were 45.4 ± 24.9 nm in diameter and composed of 160.7 ± 22.9 μg/mL iron, 247.0 ± 33.4 μg/mL platinum, and 702.6 ± 206.0 μg/mL paclitaxel. Drug release measurements showed that, at 37°C, half of the paclitaxel was released in 30.2 hours in serum and two times faster in saline. Binding assays suggested that PSMA-targeted SPMs specifically bound to C4-2 human prostate cancer cells in vitro and released paclitaxel into the cells. In vitro, paclitaxel was 2.2 and 1.6 times more cytotoxic than SPMs to C4-2 cells at 24 and 48 hours of incubation, respectively. After 72 hours of incubation, paclitaxel and SPMs were equally cytotoxic. SPMs had MRI transverse relaxivities of 389 ± 15.5 Hz/mM iron, and SIPP micelles with and without drug caused MRI contrast enhancement in vivo.

Conclusion:

Only PSMA-targeted SPMs and paclitaxel significantly prevented growth of C4-2 prostate cancer xenografts in nude mice. Furthermore, mice injected with PSMA-targeted SPMs showed significantly more paclitaxel and platinum in tumors, compared with nontargeted SPM-injected and paclitaxel-injected mice.