Engineering poly(ethylene glycol) particles for improved biodistribution

Modulating the Selectivity and Stealth Properties of Ellipsoidal Polymersomes through a Multivalent Peptide Ligand Display

There is a need for improved nanomaterials to simultaneously target cancer cells and avoid non-specific clearance by phagocytes. An ellipsoidal polymersome system is developed with a unique tunable size and shape property. These particles are functionalized with in-house phage-display cell-targeting peptide to target a medulloblastoma cell line in vitro. Particle association with medulloblastoma cells is modulated by tuning the peptide ligand density on the particles. These polymersomes has low levels of association with primary human blood phagocytes. The stealth properties of the polymersomes are further improved by including the peptide targeting moiety, an effect that is likely driven by the peptide protecting the particles from binding blood plasma proteins. Overall, this ellipsoidal polymersome system provides a promising platform to explore tumor cell targeting in vivo.

Understanding the Uptake of Nanomedicines at Different Stages of Brain Cancer Using a Modular Nanocarrier Platform and Precision Bispecific Antibodies

Increasing accumulation and retention of nanomedicines within tumor tissue is a significant challenge, particularly in the case of brain tumors where access to the tumor through the vasculature is restricted by the blood-brain barrier (BBB). This makes the application of nanomedicines in neuro-oncology often considered unfeasible, with efficacy limited to regions of significant disease progression and compromised BBB. However, little is understood about how the evolving tumor-brain physiology during disease progression affects the permeability and retention of designer nanomedicines. We report here the development of a modular nanomedicine platform that, when used in conjunction with a unique model of how tumorigenesis affects BBB integrity, allows investigation of how nanomaterial properties affect uptake and retention in brain tissue. By combining different in vivo longitudinal imaging techniques (including positron emission tomography and magnetic resonance imaging), we have evaluated the retention of nanomedicines with predefined physicochemical properties (size and surface functionality) and established a relationship between structure and tissue accumulation as a function of a new parameter that measures BBB leakiness; this offers significant advancements in our ability to relate tumor accumulation of nanomedicines to more physiologically relevant parameters. Our data show that accumulation of nanomedicines in brain tumor tissue is better correlated with the leakiness of the BBB than actual tumor volume. This was evaluated by establishing brain tumors using a spontaneous and endogenously derived glioblastoma model providing a unique opportunity to assess these parameters individually and compare the results across multiple mice. We also quantitatively demonstrate that smaller nanomedicines (20 nm) can indeed cross the BBB and accumulate in tumors at earlier stages of the disease than larger analogues, therefore opening the possibility of developing patient-specific nanoparticle treatment interventions in earlier stages of the disease. Importantly, these results provide a more predictive approach for designing efficacious personalized nanomedicines based on a particular patient's condition.

Fabrication of Poly(ethylene glycol) Capsules via Emulsion Templating Method for Targeted Drug Delivery

To reduce nonspecific interactions and circumvent biological barriers, low-fouling material of poly(ethylene glycol) (PEG) is most used for the modification of drug nanocarriers. Herein, we report the fabrication of PEG capsules via the free-radical polymerization of linear PEG or 8-arm-PEG using an emulsion templating method for targeted drug delivery. Doxorubicin (DOX) could be loaded in capsules via electrostatic interactions. The obtained capsules composed of 8-arm-PEG result in a lower cell association (2.2%) compared to those composed of linear PEG (7.3%) and, therefore, demonstrate the stealth property. The functionalization of cyclic peptides containing Arg-Gly-Asp (cRGD) on PEG capsules induce high cell targeting to U87 MG cells. A cell cytotoxicity assay demonstrates the biocompatibility of PEG capsules and high drug delivery efficacy of the targeted capsules. The reported capsules with the stealth and targeting property provide a potential platform for improved drug delivery.

Polypeptide-Based Theranostics with Tumor-Microenvironment-Activatable Cascade Reaction for Chemo-ferroptosis Combination Therapy

Nanoengineering of polymer-based therapeutic carriers is promising for precise cancer treatment. Herein, we report the fabrication of polypeptide vehicles encapsulated with anticancer drug of cisplatin (Pt drug) and Fe₃O₄ nanoparticles (denoted as Pt&Fe₃O₄@PP) as theranostics for T₂-weighted magnetic resonance imaging (MRI)-guided chemo-ferroptosis combination therapy. The number of Fe₃O₄ nanoparticles per polypeptide vehicle is well controlled by adjusting the added amount of Fe₃O₄ nanoparticles. The tumor microenvironment can trigger the release of Pt drug and Fe^2/3+, which could induce the intracellular cascade reaction to generate sufficient ^•OH for ferroptosis therapy. Moreover, the released Pt drug can cause the apoptosis of tumor cells. Meanwhile, the encapsulated Fe₃O₄ nanoparticles can also be used for T₂-weighted MRI of tumor. Both in vitro and in vivo results indicate that the reported Pt&Fe₃O₄@PP can efficiently inhibit cancer cell growth without causing significant systemic toxicity. Importantly, polypeptide vehicles could significantly reduce the side effect of free Pt drug in vivo and therefore improve the drug delivery efficacy. Our findings suggest that polypeptide-based theranostics with tumor-microenvironment-activatable cascade reaction have great potential in biomedical applications.

Stealth Coating of Nanoparticles in Drug-Delivery Systems

Nanoparticles (NPs) have emerged as a powerful drug-delivery tool for cancer therapies to enhance the specificity of drug actions, while reducing the systemic side effects. Nonetheless, NPs interact massively with the surrounding physiological environments including plasma proteins upon administration into the bloodstream. Consequently, they are rapidly cleared from the blood circulation by the mononuclear phagocyte system (MPS) or complement system, resulting in a premature elimination that will cause the drug release at off-target sites. By grafting a stealth coating layer onto the surface of NPs, the blood circulation half-life of nanomaterials can be improved by escaping the recognition and clearance of the immune system. This review focuses on the basic concept underlying the stealth behavior of NPs by polymer coating, whereby the fundamental surface coating characteristics such as molecular weight, surface chain density as well as conformations of polymer chains are of utmost importance for efficient protection of NPs. In addition, the most commonly used stealth polymers such as poly(ethylene glycol) (PEG), poly(2-oxazoline) (POx), and poly(zwitterions) in developing long-circulating NPs for drug delivery are also thoroughly discussed. The biomimetic strategies, including the cell-membrane camouflaging technique and CD47 functionalization for the development of stealth nano-delivery systems, are highlighted in this review as well.

Polyelectrolyte-Surfactant Mesomorphous Complex Templating: A Versatile Approach for Hierarchically Porous Materials

Hierarchically porous materials have attracted great attention because of their potential applications in the fields of adsorption, catalysis, and biomedical systems. The art of manipulating different templates that are used for pore construction is the key to fabricating desired hierarchically porous structures. In this feature article, the polyelectrolyte-surfactant mesomorphous complex templating (PSMCT) approach, which was first developed by our group, is elaborated on. During the organic-inorganic self-assembly, the mesomorphous complex of the polyelectrolyte and oppositely charged surfactants would undergo in situ phase separation, which is the key to fabricating hierarchically porous materials. The recent progress in the utilization of the PSMCT method for the synthesis of hierarchically porous materials with tunable morphologies, mesophases, pore structures, and compositions is reviewed. Meanwhile, the functions of the hierarchically porous materials synthesized by the PSMCT method and their applications in adsorption, catalysis, drug delivery, and nanocasting are also briefly summarized.

A Metal-Polyphenol-Coordinated Nanomedicine for Synergistic Cascade Cancer Chemotherapy and Chemodynamic Therapy

The clinical application of chemotherapy is impeded by the unsatisfactory efficacy and severe side effects. Chemodynamic therapy (CDT) has emerged as an efficient strategy for cancer treatment utilizing Fenton chemistry to destroy cancer cells by converting endogenous H2 O2 into highly toxic reactive oxygen species. Apart from the chemotherapeutic effect, cisplatin is able to act as an artificial enzyme to produce H2 O2 for CDT through cascade reactions, thus remarkably improving the anti-tumor outcomes. Herein, an organic theranostic nanomedicine (PTCG NPs) is constructed with high loading capability using epigallocatechin-3-gallate (EGCG), phenolic platinum(IV) prodrug (Pt-OH), and polyphenol modified block copolymer (PEG-b-PPOH) as the building blocks. The high stability of PTCG NPs during circulation stems from their strong metal-polyphenol coordination interactions, and efficient drug release is realized after cellular internalization. The activated cisplatin elevates the intracellular H2 O2 level through cascade reactions. This is further utilized to produce highly toxic reactive oxygen species catalyzed by an iron-based Fenton reaction. In vitro and in vivo investigations demonstrate that the combination of chemotherapy and chemodynamic therapy achieves excellent anticancer efficacy. Meanwhile, systemic toxicity faced by platinum-based drugs is avoided through this nanoformulation. This work provides a promising strategy to develop advanced nanomedicine for cascade cancer therapy.

Poly(ethylene glycol)-mediated mineralization of metal–organic frameworks

Scalable mineralization of zeolitic imidazolate framework-8 nanoparticles with versatility of cargo encapsulation and excellent colloidal dispersibility and stability is engineered using poly(ethylene glycol) as the mineralizer for therapeutic delivery.

Dual pH-Responsive Polymer Nanogels with a Core-Shell Structure for Improved Cell Association

We report the fabrication of polymer nanogels with a pH-responsive core and a pH-sheddable shell and investigate the pH-dependent cell association of the pH-responsive polymer nanogels. The pH-responsive core composed of poly(2-diisopropylaminoethyl methacrylate) (PDPA) with a pK_a ≈ 6.2 was synthesized by using polymerization in emulsion droplets. The pH-sheddable poly(ethylene glycol) (PEG) shell was coated on the amine-modified PDPA nanogels by an acid-degradable amide bond. The PEG shell is cleavable in response to the acidic tumor microenvironment, and subsequently, the surface charge of the nanogels can be reversed, which effectively enhances cellular association of these nanogels. The reported pH-responsive polymer nanogels provide a promising way for the better understanding of bio-nano interactions and potentially enrich the application of therapeutic delivery for cancer therapy.

Porous Inorganic and Hybrid Systems for Drug Delivery: Future Promise in Combatting Drug Resistance and Translation to Botanical Applications

BACKGROUND

Porous micro- and nanoparticles have the capacity to encapsulate a large quantity of therapeutics, making them promising delivery vehicles for a variety of applications. This review aims to highlight the latest development of inorganic and hybrid (inorganic/ organic) particles for drug delivery with an additional emphasis on combatting drug resistant cancer. We go one step further and discuss delivery applications beyond medicinal delivery, as there is generally a translation from medicinal delivery to botanic delivery after a short lag time.

METHODS

We undertook a search of relevant peer-reviewed publications. The quality of the relevant papers was appraised using standard tools. The characteristics of the papers are described herein, and the relevant material and therapeutic properties are discussed.

RESULTS

We discuss 4 classes of porous particles in terms of drug delivery and theranostics. We specifically focus on silica, calcium carbonate, metal-phenolic network, and metalorganic framework particles. Other relevant biomedically relevant applications are discussed and we highlight outstanding therapeutic results in the relevant literature.

CONCLUSION

The findings of this review confirm the importance of studying and utilizing porous particles for therapeutic delivery. Moreover, we show that the properties of porous particles that make them promising for medicinal drug delivery also make them promising candidates for agro-industrial applications.

Antifouling and pH-Responsive Poly(Carboxybetaine)-Based Nanoparticles for Tumor Cell Targeting

Nanocarriers with responsibility and surface functionality of targeting molecules have been widely used to improve therapeutic efficiency. Hence, we report the assembly of pH-responsive and targeted polymer nanoparticles (NPs) composed of poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) as the core and poly(carboxybetaine methacrylate) (PCBMA) as the shell, functionalized with cyclic peptides containing Arginine-Glycine-Aspartic acid-D-Phenylalanine-Lysine (RGD). The resulting polymer NPs (PDPA@PCBMA-RGD NPs) can maintain the pH-responsivity of PDPA (pKa ~6.5) and low-fouling property of PCBMA that significantly resist non-specific interactions with RAW 264.7 and HeLa cells. Meanwhile, PDPA@PCBMA-RGD NPs could specifically target αvβ3 integrin-expressed human glioblastoma (U87) cells. The pH-responsiveness and low-fouling properties of PDPA@PCBMA NPs are comparable to PDPA@poly(ethylene glycol) (PDPA@PEG) NPs, which indicates that PCBMA is an alternative to PEG for low-fouling coatings. The advantage of PDPA@PCBMA NPs lies in the presence of carboxyl groups on their surfaces for further modification (e.g., RGD functionalization for cell targeting). The reported polymer NPs represent a new carrier that have the potential for targeted therapeutic delivery.

Sono-Polymerization of Poly(ethylene glycol)-Based Nanoparticles for Targeted Drug Delivery

Engineering functional nanoparticles (NPs) with low nonspecific interactions and a high specific targeting property is highly desired for improved drug delivery. Herein, we report a targeted poly(ethylene glycol) (PEG)-based chemotherapy system synthesized via a catalyst-free sono-polymerization process for drug delivery. The polymerization process was fast (20 min), and different monomers were able to be polymerized to form NPs in a one-pot process. Glutathione (GSH)-responsive platinum prodrugs and fluorescent dyes could be encapsulated in NPs by amidation formation. Cyclic peptides containing Arg-Gly-Asp (RGD)-modified PEG-based NPs possessed a much higher cell targeting (∼90%) than the unmodified PEG-based NPs (∼10%) after a 12 h incubation with U87 MG cells, which could improve drug delivery efficacy. The IC₅₀ (50% inhibitory concentration) could also be reduced more than 50% compared to the nontargeted PEG-based NPs. Importantly, these PEG-based NPs can be freeze-dried into a powder form and redispersed in an aqueous solution without aggregation, which may facilitate the storage and transportation of nanomedicine. This study establishes a green and efficient method to engineer targeted drug carriers for drug delivery.

Characterization of Key Bio-Nano Interactions between Organosilica Nanoparticles and Candida albicans

Nanoparticle-cell interactions between silica nanomaterials and mammalian cells have been investigated extensively in the context of drug delivery, diagnostics, and imaging. While there are also opportunities for applications in infectious disease, the interactions of silica nanoparticles with pathogenic microbes are relatively underexplored. To bridge this knowledge gap, here, we investigate the effects of organosilica nanoparticles of different sizes, concentrations, and surface coatings on surface association and viability of the major human fungal pathogen Candida albicans. We show that uncoated and PEGylated organosilica nanoparticles associate with C. albicans in a size and concentration-dependent manner, but on their own, do not elicit antifungal activity. The particles are also shown to associate with human white blood cells, in a similar trend as observed with C. albicans, and remain noncytotoxic toward neutrophils. Smaller particles are shown to have low association with C. albicans in comparison to other sized particles and their association with blood cells was also observed to be minimal. We further demonstrate that by chemically immobilizing the clinically important echinocandin class antifungal drug, caspofungin, to PEGylated nanoparticles, the cell-material interaction changes from benign to antifungal, inhibiting C. albicans growth when provided in high local concentration on a surface. Our study provides the foundation for defining how organosilica particles could be tailored for clinical applications against C. albicans. Possible future developments include designing biomaterials that could detect, prevent, or treat bloodstream C. albicans infections, which at present have very high patient mortality.

Cellular Targeting of Bispecific Antibody-Functionalized Poly(ethylene glycol) Capsules: Do Shape and Size Matter?

In the present study, a capsule system that consists of a stealth carrier based on poly(ethylene glycol) (PEG) and functionalized with bispecific antibodies (BsAbs) is introduced to examine the influence of the capsule shape and size on cellular targeting. Hollow spherical and rod-shaped PEG capsules with tunable aspect ratios (ARs) of 1, 7, and 18 were synthesized and subsequently functionalized with BsAbs that exhibit dual specificities to PEG and epidermal growth factor receptor (EGFR). Dosimetry (variation between the concentrations of capsules present and capsules that reach the cell surface) was controlled through "dynamic" incubation (i.e., continuously mixing the incubation medium). The results obtained were compared with those obtained from the "static" incubation experiments. Regardless of the incubation method and the capsule shape and size studied, BsAb-functionalized PEG capsules showed >90% specific cellular association to EGFR-positive human breast cancer cells MDA-MB-468 and negligible association with both control cell lines (EGFR negative Chinese hamster ovary cells CHO-K1 and murine macrophages RAW 264.7) after incubation for 5 h. When dosimetry was controlled and the dose concentration was normalized to the capsule surface area, the size or shape had a minimal influence on the cell association behavior of the capsules. However, different cellular internalization behaviors were observed, and the capsules with ARs 7 and 18 were, respectively, the least and most optimal shape for achieving high cell internalization under both dynamic and static conditions. Dynamic incubation showed a greater impact on the internalization of rod-shaped capsules (∼58-67% change) than on the spherical capsules (∼24-29% change). The BsAb-functionalized PEG capsules reported provide a versatile particle platform for the evaluation and comparison of cellular targeting performance of capsules with different sizes and shapes in vitro.

Self-assembled green tea polyphenol-based coordination nanomaterials to improve chemotherapy efficacy by inhibition of carbonyl reductase 1

Nanomedicine has become a promising approach to improve cancer chemotherapy. It remains a major challenge how to enhance anti-drug efficacy and reduce side effects of anti-cancer drugs. Herein, we report a self-assembled nanoplatform (FDEP NPs) by integration of doxorubicin (DOX) and epigallocatechin-3-O-gallate (EGCG) with the help of coordination between Fe3+ ions and polyphenols. The EGCG from FDEP NPs could inhibit the expression of carbonyl reductase 1 (CBR1) protein and thereby inhibit the doxorubicinol (DOXOL) generation from DOX both in vitro and in vivo, thus the efficacy of DOX to cancerous cells is improved significantly. More importantly, the FDEP NPs could reduce cardiac toxicity and the DOX mediated toxicity to blood cells due to the repression of DOXOL production. Moreover, the blood half-life of FDEP NPs is longer than 23 h as determined by positron emission tomography (PET) imaging of biodistribution of radiolabelled NPs and HPLC measurement of plasma level of DOX, ensuring high tumor accumulation of FDEP NPs by enhanced permeability and retention (EPR) effect. The FDEP NPs also exhibited much improved antitumor effect over free drugs. Our work sheds new light on the engineering of nanomaterials for combination chemotherapy and may find unique clinical applications in the near future.

Link between Low-Fouling and Stealth: A Whole Blood Biomolecular Corona and Cellular Association Analysis on Nanoengineered Particles

Upon exposure to human blood, nanoengineered particles interact with a multitude of plasma components, resulting in the formation of a biomolecular corona. This corona modulates downstream biological responses, including recognition by and association with human immune cells. Considerable research effort has been directed toward the design of materials that can demonstrate a low affinity for various proteins (low-fouling materials) and materials that can exhibit low association with human immune cells (stealth materials). An implicit assumption common to bio-nano research is that nanoengineered particles that are low-fouling will also exhibit stealth. Herein, we investigated the link between the low-fouling properties of a particle and its propensity for stealth in whole human blood. High-fouling mesoporous silica (MS) particles and low-fouling zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) particles were synthesized, and their interaction with blood components was assessed before and after precoating with serum albumin, immunoglobulin G, or complement protein C1q. We performed an in-depth proteomics characterization of the biomolecular corona that both identifies specific proteins and measures their relative abundance. This was compared with observations from a whole blood association assay that identified with which cell type each particle system associates. PMPC-based particles displayed reduced association both with cells and with serum proteins compared with MS-based particles. Furthermore, the enrichment of specific proteins within the biomolecular corona was found to correlate with association with specific cell types. This study demonstrates how the low-fouling properties of a material are indicative of its stealth with respect to immune cell association.

Modulating Targeting of Poly(ethylene glycol) Particles to Tumor Cells Using Bispecific Antibodies

Low-fouling or "stealth" particles composed of poly(ethylene glycol) (PEG) display a striking ability to evade phagocytic cell uptake. However, functionalizing them for specific targeting is challenging. To address this challenge, stealth PEG particles prepared by a mesoporous silica templating method are functionalized with bispecific antibodies (BsAbs) to obtain PEG-BsAb particles via a one-step binding strategy for cell and tumor targeting. The dual specificity of the BsAbs-one arm binds to the PEG particles while the other targets a cell antigen (epidermal growth factor receptor, EGFR)-is exploited to modulate the number of targeting ligands per particle. Increasing the BsAb incubation concentration increases the amount of BsAb tethered to the PEG particles and enhances targeting and internalization into breast cancer cells overexpressing EGFR. The degree of BsAb functionalization does not significantly reduce the stealth properties of the PEG particles ex vivo, as assessed by their interactions with primary human blood granulocytes and monocytes. Although increasing the BsAb amount on PEG particles does not lead to the expected improvement in tumor accumulation in vivo, BsAb functionalization facilitates tumor cell uptake of PEG particles. This work highlights strategies to balance evading nonspecific clearance pathways, while improving tumor targeting and accumulation.

Modular Metal-Organic Polyhedra Superassembly: From Molecular-Level Design to Targeted Drug Delivery

Targeted drug delivery remains at the forefront of biomedical research but remains a challenge to date. Herein, the first superassembly of nanosized metal-organic polyhedra (MOP) and their biomimetic coatings of lipid bilayers are described to synergistically combine the advantages of micelles and supramolecular coordination cages for targeted drug delivery. The superassembly technique affords unique hydrophobic features that endow individual MOP to act as nanobuilding blocks and enable their superassembly into larger and well-defined nanocarriers with homogeneous sizes over a broad range of diameters. Various cargos are controllably loaded into the MOP with high payloads, and the nanocages are then superassembled to form multidrug delivery systems. Additionally, functional nanoparticles are introduced into the superassemblies via a one-pot process for versatile bioapplications. The MOP superassemblies are surface-engineered with epidermal growth factor receptors and can be targeted to cancer cells. In vivo studies indicated the assemblies to have a substantial circulation half-life of 5.6 h and to undergo renal clearance-characteristics needed for nanomedicines.

Engineering Antibodies with C-Terminal Sortase-Mediated Modification for Targeted Nanomedicine

The current advances in nanoengineered materials coupled with the precise targeting capability of recombinant antibodies can create nanoscale diagnostics and therapeutics which show enhanced accumulation and extended retention at a target tissue. Smaller antibodies such as single-chain variable fragments (scFv) preserve the selective and strong binding of their parent antibody to their antigen with the benefits of low immunogenicity, more efficient tissue penetration and easy introduction of functional residues suitable for site-specific conjugation. This is of high importance as nonspecific antibody modification often involves attachment to free cysteine or lysine amino acids which may reside in the active site, leading to reduced antigen binding.In this chapter, we outline a facile and versatile chemoenzymatic approach for production of targeted nanocarrier scFv conjugates using the bacterial trans-peptidase Sortase A (Srt A). Srt A efficiently mediates sequence-specific peptide ligation under mild conditions and has few undesirable side reactions. We first describe the production, purification and characterization of Srt A enzyme and a scFv construct which targets activated platelets, called scFv_{anti-GPIIb/IIIa}. Following this, our protocol illustrates the chemoenzymatic modification of the antibody at the C-terminus with an orthogonal click chemistry linker. This avoids any random attachment to the biologically active antigen binding site of the antibody. Finally, we describe the modification of a nanoparticle surface with scFv attachment via two methods: (1) direct Sortase-mediated conjugation; or (2) a two-step system which consists of scFv Sortase-mediated conjugation followed by strain promoted azide-alkyne cycloaddition. Finally, methodology is described to assess the successful assembly of targeted particles.

Highly-Soluble Cyanine J-aggregates Entrapped by Liposomes for In Vivo Optical Imaging around 930 nm

Near infrared (NIR) dyes are useful for in vivo optical imaging. Liposomes have been used extensively for delivery of diverse cargos, including hydrophilic cargos which are passively loaded in the aqueous core. However, most currently available NIR dyes are only slightly soluble in water, making passive entrapment in liposomes challenging for achieving high optical contrast.

Methods: We modified a commercially-available NIR dye (IR-820) via one-step Suzuki coupling with dicarboxyphenylboronic acid, generating a disulfonated heptamethine; dicarboxyphenyl cyanine (DCP-Cy). DCP-Cy was loaded in liposomes and used for optical imaging.

Results: Owing to increased charge in mildly basic aqueous solution, DCP-Cy had substantially higher water solubility than indocyanine green (by an order of magnitude), resulting in higher NIR absorption. Unexpectedly, DCP-Cy tended to form J-aggregates with pronounced spectral red-shifting to 934 nm (from 789 nm in monomeric form). J-aggregate formation was dependent on salt and DCP-Cy concentration. Dissolved at 20 mg/mL, DCP-Cy J-aggregates could be entrapped in liposomes. Full width at half maximum absorption of the liposome-entrapped dye was just 25 nm. The entrapped DCP-Cy was readily detectable by fluorescence and photoacoustic NIR imaging. Upon intravenous administration to mice, liposomal DCP-Cy circulated substantially longer than the free dye. Accumulation was largely in the spleen, which was visualized with fluorescence and photoacoustic imaging.

Conclusions: DCP-Cy is simple to synthesize and exhibits high aqueous solubility and red-shifted absorption from J-aggregate formation. Liposomal dye entrapment is possible, which facilitates in vivo photoacoustic and fluorescence imaging around 930 nm.

Theragnostic potentials of core/shell mesoporous silica nanostructures

Theragnostics is considered as an emerging treatment strategy that integrates therapeutics and diagnostics thus allowing delivery of therapeutics and simultaneous monitoring of the progression of treatment. Among the different types of inorganic nanomaterials that are being used for nanomedicine, core shell mesoporous silica nanoparticles have emerged as promising multifunctional nanoplatform for theragnostic application. Research in the design of core/shell mesoporous silica nanoparticles is steadily diversifying owing to the various interesting properties of these nanomaterials that are advantageous for advanced biomedical applications. Core/shell mesoporous silica nanoparticles, have garnered substantial attention in recent years because of their exceptional properties including large surface area, low density, ease of functionalization, high loading capacity of drugs, control of the morphology, particle size, tunable hollow interior space and mesoporous shell and possibility of incorporating multifunctional interior core material. In the past decade researcher's demonstrated tremendous development in design of functionalized core/shell mesoporous silica nanoparticles with different inorganic functional nanomaterial incorporated into mesoporous nanosystem for simultaneous therapeutic and diagnostic (theragnostic) applications in cancer. In this review, we recapitulate the progress in commonly used synthetic strategies and theragnostic applications of core/shell mesoporous silica nanoparticles with special emphasis on therapeutic and diagnostic modalities. Finally, we discuss the challenges and some perspectives on the future research and development of theragnostic core/shell mesoporous silica nanoparticles.

Novel PEGylated Liposomes Enhance Immunostimulating Activity of isRNA

The performance of cationic liposomes for delivery of therapeutic nucleic acids in vivo can be improved and specifically tailored to certain types of cargo and target cells by incorporation of PEG-containing lipoconjugates in the cationic liposome's composition. Here, we report on the synthesis of novel PEG-containing lipoconjugates with molecular masses of PEG 800, 1500 and 2000 Da. PEG-containing lipoconjugates were used as one of the components in liposome preparation with the polycationic amphiphile 1,26-bis(cholest-5-en-3β-yloxycarbonylamino)-7,11,16,20-tetra-azahexacosan tetrahydrochloride (2X3) and the lipid-helper dioleoylphosphatidylethanolamine (DOPE). We demonstrate that increasing the length of the PEG chain reduces the transfection activity of liposomes in vitro, but improves the biodistribution, increases the circulation time in the bloodstream and enhances the interferon-inducing activity of immunostimulating RNA in vivo.

Gel-Mediated Electrospray Assembly of Silica Supraparticles for Sustained Drug Delivery

Supraparticles (SPs) composed of smaller colloidal particles provide a platform for the long-term, controlled release of therapeutics in biomedical applications. However, current synthesis methods used to achieve high drug loading and those involving biocompatible materials are often tedious and low throughput, thereby limiting the translation of SPs to diverse applications. Herein, we present a simple, effective, and automatable alginate-mediated electrospray technique for the assembly of robust spherical silica SPs (Si-SPs) for long-term (>4 months) drug delivery. The Si-SPs are composed of either porous or nonporous primary Si particles within a decomposable alginate matrix. The size and shape of the Si-SPs can be tailored by controlling the concentrations of alginate and silica primary particles used and key electrospraying parameters, such as flow rate, voltage, and collector distance. Furthermore, the performance (including drug loading kinetics, loading capacity, loading efficiency, and drug release) of the Si-SPs can be tuned by changing the porosity of the primary particles and through the retention or removal (via calcination) of the alginate matrix. The structure and morphology of the Si-SPs were characterized by electron microscopy, dynamic light scattering, N₂ adsorption-desorption analysis, and X-ray photoelectron spectroscopy. The cytotoxicity and degradability of the Si-SPs were also examined. Drug loading kinetics and loading capacity for six different types of Si-SPs, using a model protein drug (fluorescently labeled lysozyme), demonstrate that Si-SPs prepared from primary silica particles with large pores can load significant amounts of lysozyme (∼10 μg per SP) and exhibit sustained, long-term release of more than 150 days. Our experiments show that Si-SPs can be produced through a gel-mediated electrospray technique that is robust and automatable (important for clinical translation and commercialization) and that they present a promising platform for long-term drug delivery.

Nanoengineering of Poly(ethylene glycol) Particles for Stealth and Targeting

The assembly of particles composed solely or mainly of poly(ethylene glycol) (PEG) is an emerging area that is gaining increasing interest within bio-nano science. PEG, widely considered to be the "gold standard" among polymers for drug delivery, is providing a platform for exploring fundamental questions and phenomena at the interface between particle engineering and biomedicine. These include the targeting and stealth behaviors of synthetic nanomaterials in biological environments. In this feature article, we discuss recent work in the nanoengineering of PEG particles and explore how they are enabling improved targeting and stealth performance. Specific examples include PEG particles prepared through surface-initiated polymerization, mesoporous silica replication via postinfiltration, and particle assembly through metal-phenolic coordination. This particle class exhibits unique in vivo behavior (e.g., biodistribution and immune cell interactions) and has recently been explored for drug delivery applications.

Understanding Effects of PAMAM Dendrimer Size and Surface Chemistry on Serum Protein Binding with Discrete Molecular Dynamics Simulations

Polyamidoamine (PAMAM) dendrimers, a class of polymeric nanoparticles (NPs) with highly-controllable sizes and surface chemistry, are promising candidates for many biomedical applications, including drug and gene delivery, imaging, and inhibition of amyloid aggregation. In circulation, binding of serum proteins with dendritic NPs renders the formation of protein corona and alters the biological identity of the NP core, which may subsequently elicit immunoresponse and cytotoxicity. Understanding the effects of PAMAM size and surface chemistry on serum protein binding is, therefore, crucial to enable their broad biomedical applications. Here, by applying atomistic discrete molecular dynamics (DMD) simulations, we first uncovered the binding of PAMAM with HSA and Ig and detailed the dependences of such binding on PAMAM size and surface modification. Compared to either anionic or cationic surfaces, modifications with neutral phosphorylcholine (PC), polyethylene glycol (PEG), and hydroxyls (OH) significantly reduced binding with proteins. The relatively strong binding between proteins and PAMAM dendrimers with charged surface groups was mainly driven by electrostatic interactions as well as hydrophobic interactions. Using steered DMD (SDMD) simulations, we conducted a force-pulling experiment in silico estimating the critical forces separating PAMAM-protein complexes and deriving the corresponding free energy barriers for dissociation. The SDMD-derived HSA-binding affinities were consistent with existing experimental measurements. Our results highlighted the association dynamics of protein-dendrimer interactions and binding affinities, whose implications range from fundamental nanobio interfacial phenomena to the development of "stealth NPs".

Self-Assembled Metal-Phenolic Networks on Emulsions as Low-Fouling and pH-Responsive Particles

Interfacial self-assembly is a powerful organizational force for fabricating functional nanomaterials, including nanocarriers, for imaging and drug delivery. Herein, the interfacial self-assembly of pH-responsive metal-phenolic networks (MPNs) on the liquid-liquid interface of oil-in-water emulsions is reported. Oleic acid emulsions of 100-250 nm in diameter are generated by ultrasonication, to which poly(ethylene glycol) (PEG)-based polyphenolic ligands are assembled with simultaneous crosslinking by metal ions, thus forming an interfacial MPN. PEG provides a protective barrier on the emulsion phase and renders the emulsion low fouling. The MPN-coated emulsions have a similar size and dispersity, but an enhanced stability when compared with the uncoated emulsions, and exhibit a low cell association in vitro, a blood circulation half-life of ≈50 min in vivo, and are nontoxic to healthy mice. Furthermore, a model anticancer drug, doxorubicin, can be encapsulated within the emulsion phase at a high loading capacity (≈5 fg of doxorubicin per emulsion particle). The MPN coating imparts pH-responsiveness to the drug-loaded emulsions, leading to drug release at cell internalization pH and a potent cell cytotoxicity. The results highlight a straightforward strategy for the interfacial nanofabrication of pH-responsive emulsion-MPN systems with potential use in biomedical applications.

Uptake and transcytosis of functionalized superparamagnetic iron oxide nanoparticles in an in vitro blood brain barrier model

Two major hurdles in nanomedicine are the limited strategies for synthesizing stealth nanoparticles and the poor efficacy of the nanoparticles in translocating across the blood brain barrier (BBB). Here we examined the uptake and transcytosis of iron oxide nanoparticles (IONPs) grafted with biomimetic phosphorylcholine (PC) brushes in an in vitro BBB model system, and compared them with bare, PEG or PC-PEG mixture grafted IONPs. Hyperspectral imaging indicated IONP co-localization with cells. Quantitative analysis with total reflection X-ray fluorescence spectrometry showed that after 24 h, 78% of PC grafted, 68-69% of PEG or PC-PEG grafted, and 30% of bare IONPs were taken up by the BBB. Transcytosis of IONPs was time-dependent and after 24 h, 16-17% of PC or PC-PEG mixture grafted IONPs had passed the BBB model, significantly more than PEG grafted or bare IONPs. These findings point out that grafting of IONPs with PC is a viable strategy for improving the uptake and transcytosis of nanoparticles.

Low-Fouling and Biodegradable Protein-Based Particles for Thrombus Imaging

Nanomedicine holds great promise for vascular disease diagnosis and specific therapy, yet rapid sequestration by the mononuclear phagocytic system limits the efficacy of particle-based agents. The use of low-fouling polymers, such as poly(ethylene glycol), efficiently reduces this immune recognition, but these nondegradable polymers can accumulate in the human body and may cause adverse effects after prolonged use. Thus, new particle formulations combining stealth, low immunogenicity and biocompatible features are required to enable clinical use. Here, a low-fouling particle platform is described using exclusively protein material. A recombinant protein with superior hydrophilic characteristics provided by the amino acid repeat proline, alanine, and serine (PAS) is designed and cross-linked into particles with lysine (K) and polyglutamic acid (E) using mesoporous silica templating. The obtained PASKE particles have low-fouling behavior, have a prolonged circulation time compared to albumin-based particles, and are rapidly degraded in the cell's lysosomal compartment. When labeled with near-infrared fluorescent molecules and functionalized with an anti-glycoprotein IIb/IIIa single-chain antibody targeting activated platelets, the particles show potential as a noninvasive molecular imaging tool in a mouse model of carotid artery thrombosis. The PASKE particles constitute a promising biodegradable and versatile platform for molecular imaging of vascular diseases.

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano-/micro-superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.

Mechanobiological Mimicry of Helper T Lymphocytes to Evaluate Cell-Biomaterials Crosstalk

The unique properties of immune cells have inspired many efforts in engineering advanced biomaterials capable of mimicking their behaviors. However, an inclusive model capable of mimicking immune cells in different situations remains lacking. Such models can provide invaluable data for understanding immune-biomaterial crosstalk. Inspired by CD4+ T cells, polymeric microparticles with physicochemical properties similar to naïve and active T cells are engineered. A lipid coating is applied to enhance their resemblance and provide a platform for conjugation of desired antibodies. A novel dual gelation approach is used to tune the elastic modulus and flexibility of particles, which also leads to elongated circulation times. Furthermore, the model is enriched with magnetic particles so that magnetotaxis resembles the chemotaxis of cells. Also, interleukin-2, a proliferation booster, and interferon-γ cytokines are loaded into the particles to manipulate the fates of killer T cells and mesenchymal stem cells, respectively. The penetration of these particles into 3D environments is studied to provide in vitro models of immune-biomaterials crosstalk. This biomimicry model enables optimization of design parameters required for engineering more efficient drug carriers and serves as a potent replica for understanding the mechanical behavior of immune cells.

The Effect of Molecular Structure on Cytotoxicity and Antitumor Activity of PEGylated Nanomedicines

Fundamental studies on the cellular uptake and drug release of PEGylated nanomedicines are beneficial to understand their fate in vivo and construct ideal nanoparticle formulations. In this work, the detailed metabolic process of PEGylated doxorubicin (Dox) nanomedicines were investigated via confocal laser scanning microscopy (CLSM), flow cytometry (FCM), cytotoxicity test, fluorescence imaging in vivo (FLIV) and liquid chromatography tandem mass spectrometry (LC-MS/MS). Among them, only LC-MS/MS could accurately determine the content of PEGylated Dox and Dox in vitro and in vivo. To the best of our knowledge, this was the first time the PEGylated Dox and released Dox were simultaneously quantified. The interplay of molecular structures, cellular uptake, drug release, and antitumor effect was well characterized. PEG with high molecular weight impeded the cellular uptake of nanoparticles, and the acid-labile hydrazone bond between Dox and PEG promoted Dox release significantly. Cellular uptake and drug release play decisive roles in cytotoxicity and antitumor effect, as evidenced by LC-MS/MS. We emphasized that LC-MS/MS would be a practicable method to quantify PEGylated drugs without complex tags, which could be more in-depth to understand the interaction between PEGylated nanomedicines and their antitumor efficacy.

Understanding the Effects of Nanocapsular Mechanical Property on Passive and Active Tumor Targeting

The physicochemical properties of nanoparticles (size, charge, and surface chemistry, etc.) influence their biological functions often in complex and poorly understood ways. This complexity is compounded when the nanostructures involved have variable mechanical properties. Here, we report the synthesis of liquid-filled silica nanocapsules (SNCs, ∼ 150 nm) having a wide range of stiffness (with Young's moduli ranging from 704 kPa to 9.7 GPa). We demonstrate a complex trade-off between nanoparticle stiffness and the efficiencies of both immune evasion and passive/active tumor targeting. Soft SNCs showed 3 times less uptake by macrophages than stiff SNCs, while the uptake of PEGylated SNCs by cancer cells was independent of stiffness. In addition, the functionalization of stiff SNCs with folic acid significantly enhanced their receptor-mediated cellular uptake, whereas little improvement for the soft SNCs was conferred. Further in vivo experiments confirmed these findings and demonstrated the critical role of nanoparticle mechanical properties in regulating their interactions with biological systems.

Toxic Reactive Oxygen Species Enhanced Synergistic Combination Therapy by Self-Assembled Metal-Phenolic Network Nanoparticles

Engineering functional nanomaterials with high therapeutic efficacy and minimum side effects has increasingly become a promising strategy for cancer treatment. Herein, a reactive oxygen species (ROS) enhanced combination chemotherapy platform is designed via a biocompatible metal-polyphenol networks self-assembly process by encapsulating doxorubicin (DOX) and platinum prodrugs in nanoparticles. Both DOX and platinum drugs can activate nicotinamide adenine dinucleotide phosphate oxidases, generating superoxide radicals (O₂^•- ). The superoxide dismutase-like activity of polyphenols can catalyze H₂ O₂ generation from O₂^•- . Finally, the highly toxic HO^• free radicals are generated by a Fenton reaction. The ROS HO^• can synergize the chemotherapy by a cascade of bioreactions. Positron emission tomography imaging of ⁸⁹ Zr-labeled as-prepared DOX@Pt prodrug Fe³⁺ nanoparticles (DPPF NPs) shows prolonged blood circulation and high tumor accumulation. Furthermore, the DPPF NPs can effectively inhibit tumor growth and reduce the side effects of anticancer drugs. This study establishes a novel ROS promoted synergistic nanomedicine platform for cancer therapy.

Preventing Obstructions of Nanosized Drug Delivery Systems by the Extracellular Matrix

Although nanosized drug delivery systems are promising tools for the treatment of severe diseases, the extracellular matrix (ECM) constitutes a major obstacle that endangers therapeutic success. Mobility of diffusing species is restricted not only by small pore size (down to as low as 3 nm) but also by electrostatic interactions with the network. This article evaluates commonly used in vitro models of ECM, analytical methods, and particle types with respect to their similarity to native conditions in the target tissue. In this cross-study evaluation, results from a wide variety of mobility studies are analyzed to discern general principles of particle-ECM interactions. For instance, cross-linked networks and a negative network charge are essential to reliably recapitulate key features of the native ECM. Commonly used ECM mimics comprised of one or two components can lead to mobility calculations which have low fidelity to in vivo results. In addition, analytical methods must be tailored to the properties of both the matrix and the diffusing species to deliver accurate results. Finally, nanoparticles must be sufficiently small to penetrate the matrix pores (ideally R_d/p < 0.5; d = particle diameter, p = pore size) and carry a neutral surface charge to avoid obstructions. Larger (R_d/p >> 1) or positively charged particles are trapped.

Polymer Therapeutics: Biomarkers and New Approaches for Personalized Cancer Treatment

Polymer therapeutics (PTs) provides a potentially exciting approach for the treatment of many diseases by enhancing aqueous solubility and altering drug pharmacokinetics at both the whole organism and subcellular level leading to improved therapeutic outcomes. However, the failure of many polymer-drug conjugates in clinical trials suggests that we may need to stratify patients in order to match each patient to the right PT. In this concise review, we hope to assess potential PT-specific biomarkers for cancer treatment, with a focus on new studies, detection methods, new models and the opportunities this knowledge will bring for the development of novel PT-based anti-cancer strategies. We discuss the various "hurdles" that a given PT faces on its passage from the syringe to the tumor (and beyond), including the passage through the bloodstream, tumor targeting, tumor uptake and the intracellular release of the active agent. However, we also discuss other relevant concepts and new considerations in the field, which we hope will provide new insight into the possible applications of PT-related biomarkers.

Layer-by-Layer Engineered Polymer Capsules for Therapeutic Delivery

Polymer capsules fabricated via layer-by-layer (LbL) assembly have emerged as promising carriers for therapeutic delivery. The versatile assembly technique allows an extensive choice of materials to be incorporated as constituents of the multilayers, which therefore endow capsules with specific properties and functionalities. This chapter describes protocols for fabrication of LbL-engineered poly(methacrylic acid) (PMA) capsules for applications in gene delivery, including (1) synthesis of building blocks, (2) cargo encapsulation, (3) multilayer film formation, (4) surface modification, and (5) cross-linking of multilayer films and dissolution of particle templates. DNA is adsorbed onto positively charged silica particle templates, followed by formation of polymer films via hydrogen-bonded multilayers of thiol-functionalized PMA and poly(N-vinylpyrrolidone) (PVP). The outer polymer membranes can be surface modified with copolymers of PMA and poly(ethylene glycol) (PEG). Upon film stabilization and dissolution of particle templates, disulfide-cross-linked DNA-loaded PMA capsules are obtained, which serve as therapeutic carriers that can degrade and facilitate cargo release in intracellular reducing environment.

Particle Targeting in Complex Biological Media

Over the past few decades, nanoengineered particles have gained increasing interest for applications in the biomedical realm, including diagnosis, imaging, and therapy. When functionalized with targeting ligands, these particles have the potential to interact with specific cells and tissues, and accumulate at desired target sites, reducing side effects and improve overall efficacy in applications such as vaccination and drug delivery. However, when targeted particles enter a complex biological environment, the adsorption of biomolecules and the formation of a surface coating (e.g., a protein corona) changes the properties of the carriers and can render their behavior unpredictable. For this reason, it is of importance to consider the potential challenges imposed by the biological environment at the early stages of particle design. This review describes parameters that affect the targeting ability of particulate drug carriers, with an emphasis on the effect of the protein corona. We highlight strategies for exploiting the protein corona to improve the targeting ability of particles. Finally, we provide suggestions for complementing current in vitro assays used for the evaluation of targeting and carrier efficacy with new and emerging techniques (e.g., 3D models and flow-based technologies) to advance fundamental understanding in bio-nano science and to accelerate the development of targeted particles for biomedical applications.

Templated Polymer Replica Nanoparticles to Facilitate Assessment of Material-Dependent Pharmacokinetics and Biodistribution

Surface modification is frequently used to tailor the interactions of nanoparticles with biological systems. In many cases, the chemical nature of the treatments employed to modify the biological interface (for example attachment of hydrophilic polymers or targeting groups) is the focus of attention. However, isolation of the fundamental effects of the materials employed to modify the interface are often confounded by secondary effects imparted by the underlying substrate. Herein, we demonstrate that polymer replica particles templated from degradable mesoporous silica provide a facile means to evaluate the impact of surface modification on the biological interactions of nanomaterials, independent of the substrate. Poly(ethylene glycol) (PEG), poly(N-(2 hydroxypropyl)methacrylamide) (PHPMA), and poly(methacrylic acid) (PMA) were templated onto mesoporous silica and cross-linked and the residual particles were removed. The resulting nanoparticles, comprising interfacial polymer alone, were then investigated using a range of in vitro and in vivo tests. As expected, the PEG particles showed the best stealth properties, and these trends were consistent in both in vitro and in vivo studies. PMA particles showed the highest cell association in cell lines in vitro and were rapidly taken up by monocytes in ex vivo whole blood, properties consistent with the very high in vivo clearance subsequently seen in rats. In contrast, PHPMA particles showed rapid association with both granulocytes and monocytes in ex vivo whole blood, even though in vivo clearance was less rapid than the PMA particles. Rat studies confirmed better systemic exposure for PEG and PHPMA particles when compared to PMA particles. This study provides a new avenue for investigating material-dependent biological behaviors of polymer particles, irrespective of the properties of the underlying core, and provides insights for the selection of polymer particles for future biological applications.

Polymer-coated superparamagnetic iron oxide nanoparticles as T2 contrast agent for MRI and their uptake in liver

Aim:

To study the efficiency of multifunctional polymer-based superparamagnetic iron oxide nanoparticles (bioferrofluids) as a T₂ magnetic resonance contrast agent and their uptake and toxicity in liver.

Materials & methods:

Mice were intravenously injected with bioferrofluids and Endorem^®. The magnetic resonance efficiency, uptake and in vivo toxicity were investigated by means of magnetic resonance imaging (MRI) and histological techniques.

Results:

Bioferrofluids are a good T₂ contrast agent with a higher r₂/r₁ ratio than Endorem. Bioferrofluids have a shorter blood circulation time and persist in liver for longer time period compared with Endorem. Both bioferrofluids and Endorem do not generate any noticeable histological lesions in liver over a period of 60 days post-injection.

Conclusion:

Our bioferrofluids are powerful diagnostic tool without any observed toxicity over a period of 60 days post-injection.

Several superparamagnetic iron oxide nanoparticles (SPIONs) preparations have been approved by US FDA for clinical use as MRI contrast agents. In recent years, we have been developing a synthetic multifunctional platform for SPIONs based on the use of polymers. In this report, we explored the diagnostic potential of these nanoparticles (herein called bioferrofluids) as an MRI contrast agent and their uptake in liver, without neglecting their toxicological effects. Results show that our bioferrofluids are a good T₂ contrast agent without any observed toxicity in liver.