Targeted Hyperbranched Nanoparticles for Delivery of Doxorubicin in Breast Cancer Brain Metastasis

Breast cancer brain metastases (BM) are associated with a dismal prognosis and very limited treatment options. Standard chemotherapy is challenging in BM patients because the high dosage required for an effective outcome causes unacceptable systemic toxicities, a consequence of poor brain penetration, and a short physiological half-life. Nanomedicines have the potential to circumvent off-target toxicities and factors limiting the efficacy of conventional chemotherapy. The HER3 receptor is commonly expressed in breast cancer BM. Here, we investigate the use of hyperbranched polymers (HBP) functionalized with a HER3 bispecific-antibody fragment for cancer cell-specific targeting and pH-responsive release of doxorubicin (DOX) to selectively deliver and treat BM. We demonstrated that DOX-release from the HBP carrier was controlled, gradual, and greater in endosomal acidic conditions (pH 5.5) relative to physiologic pH (pH 7.4). We showed that the HER3-targeted HBP with DOX payload was HER3-specific and induced cytotoxicity in BT474 breast cancer cells (IC50: 17.6 μg/mL). Therapeutic testing in a BM mouse model showed that HER3-targeted HBP with DOX payload impacted tumor proliferation, reduced tumor size, and prolonged overall survival. HER3-targeted HBP level detected in ex vivo brain samples was 14-fold more than untargeted-HBP. The HBP treatments were well tolerated, with less cardiac and oocyte toxicity compared to free DOX. Taken together, our HER3-targeted HBP nanomedicine has the potential to deliver chemotherapy to BM while reducing chemotherapy-associated toxicities.

An immunomodulating peptide with potential to suppress tumour growth and autoimmunity

Cancers and autoimmune diseases commonly co-exist and immune checkpoint inhibitor therapy (ICI) exacerbates autoimmune pathologies. We recently described a lipidic peptide, designated IK14004, that promotes expansion of immunosuppressive T regulatory (Treg) cells and uncouples interleukin-2 from interferon-gamma production while activating CD8+ T cells. Herein, we report IK14004-mediated inhibition of Lewis lung cancer (LLC) growth and re-invigoration of splenocyte-derived exhausted CD4+ T cells. In human immune cells from healthy donors, IK14004 modulates expression of the T cell receptor α/β subunits, induces Type I IFN expression, stimulates natural killer (NK) cells to express NKG2D/NKp44 receptors and enhances K562 cytotoxicity. In both T and NK cells, IK14004 alters the IL-12 receptor β1/β2 chain ratio to favour IL-12p70 binding. Taken together, this novel peptide offers an opportunity to gain further insight into the complexity of ICI immunotherapy so that autoimmune responses may be minimised without promoting tumour evasion from the immune system.

Exploring the impact of severity in hepatic fibrosis disease on the intrahepatic distribution of novel biodegradable nanoparticles targeted towards different disease biomarkers

Nanoparticle-based drug delivery systems (DDS) have shown promising results in reversing hepatic fibrosis, a common pathological basis of chronic liver diseases (CLDs), in preclinical animal models. However, none of these nanoparticle formulations has transitioned to clinical usage and there are currently no FDA-approved drugs available for liver fibrosis. This highlights the need for a better understanding of the challenges faced by nanoparticles in this complex disease setting. Here, we have systematically studied the impact of targeting strategy, the degree of macrophage infiltration during fibrosis, and the severity of fibrosis, on the liver uptake and intrahepatic distribution of nanocarriers. When tested in mice with advanced liver fibrosis, we demonstrated that the targeting ligand density plays a significant role in determining the uptake and retention of the nanoparticles in the fibrotic liver whilst the type of targeting ligand modulates the trafficking of these nanoparticles into the cell population of interest - activated hepatic stellate cells (aHSCs). Engineering the targeting strategy indeed reduced the uptake of nanoparticles in typical mononuclear phagocyte (MPS) cell populations, but not the infiltrated macrophages. Meanwhile, additional functionalization may be required to enhance the efficacy of DDS in end-stage fibrosis/cirrhosis compared to early stages.

RAFT Polymer-Antibody Conjugation: Squaramide Ester Chemistry Leads to Conjugates with a Therapeutic Anti-EGFR Antibody with Full Retention of Activity and Increased Tumor Uptake In Vivo

Covalent conjugation of a biologically stable polymer to a therapeutic protein, e.g., an antibody, holds many benefits such as prolonged plasma exposure of the protein and improved tumor uptake. Generation of defined conjugates is advantageous in many applications, and a range of site-selective conjugation methods have been reported. Many current coupling methods lead to dispersity in coupling efficiencies with subsequent conjugates of less-well-defined structure, which impacts reproducibility of manufacture and ultimately may impact successful translation to treat or image diseases. We explored designing stable, reactive groups for polymer conjugation reactions that would lead to conjugates through the simplest and most abundant residue on most proteins, the lysine residue, yielding conjugates in high purity and demonstrating retention of mAb efficacy through surface plasmon resonance (SPR), cell targeting, and in vivo tumor targeting. We utilized squaric acid diesters as coupling agents for selective amidation of lysine residues and were able to selectively conjugate one, or two, high-molecular-weight polymers to a therapeutically relevant antibody, 528mAb, that subsequently retained full binding specificity. Water-soluble copolymers of N-(2-hydroxypropyl) methacrylamide (HPMA) and N-isopropylacrylamide (NIPAM) were prepared by Reversible Addition-Fragmentation chain-Transfer (RAFT) polymerization and we demonstrated that a dual-dye-labeled antibody-RAFT conjugate (528mAb-RAFT) exhibited effective tumor targeting in model breast cancer xenografts in mice. The combination of the precise and selective squaric acid ester conjugation method, with the use of RAFT polymers, leads to a promising strategic partnership for improved therapeutic protein-polymer conjugates having a very-well-defined structure.

Development and Validation of a Targeted Treatment for Brain Tumors Using a Multi-Drug Loaded, Relapse-Resistant Polymeric Theranostic

This study aimed to develop a multifunctional polymer platform that could address the issue of treatment resistance when using conventional chemotherapeutics to treat glioblastoma (GBM). An antibody-conjugated, multi-drug loaded hyperbranched polymer was developed that provided a platform to evaluate the role of targeted nanomedicine treatments in overcoming resistant GBM by addressing the various complications with current clinically administered formulations. The polymer was synthesized via reversible addition fragmentation chain transfer polymerization and included the clinical first-line alkylating agent temozolomide (TMZ) which was incorporated as a polymerizable monomer, poly (ethylene glycol) (PEG) units to impart biocompatibility and enable conjugation with αPEG-αEphA2 bispecific antibody (αEphA2 BsAb) for tumor targeting, and hydrazide moieties for attachment of a secondary drug which allows exploration of synergistic therapies. To overcome the resistance to TMZ, the O⁶ alkylguanine DNA alkyltransferase (AGT, DNA repair protein) inhibitor, dialdehyde O⁶ benzylguanine (DABG) was subsequently conjugated to the polymer via an acid labile hydrazone linker to facilitate controlled release under conditions encountered within the tumor microenvironment. The prolonged degradation half-life (4-5 h) of the polymer conjugated TMZ in vitro offered a potential avenue to overcome the inability to deliver these drugs in combination at therapeutic doses. Although only 20% of DABG could be released within the studied timeframe (192 h) under conditions mimicking the acidic nature of the tumor environment, cytotoxicity evaluation using cell assays confirmed the improved therapeutic efficacy toward resistant GBM cells after attaching DABG to the polymer delivery vehicle. Of note, when the polymeric delivery vehicle was specifically targeted to receptors (Ephrin A2) on the surface of the GBM cells using our in-house developed EphA2 specific BsAb, the dual-drug-loaded polymer exhibited an improved therapeutic effect on TMZ-resistant cells compared to the free drug combination. Both in vitro and in vivo targeting studies showed high uptake of the construct to GBM tumors with an upregulated EphA2 receptor (T98G and U251) compared to a tumor that had low expression (U87MG), where a dual tumor xenograft model was used to demonstrate the enhanced accumulation in tumor tissue in vivo. Despite the synthetic challenges of developing systems to effectively deliver controlled doses of TMZ and DABG, these studies highlight the potential benefit of this formulation for delivering multi-drug combinations to resistant GBM tumor cells and offer a platform for future optimization in therapeutic studies.

Efficient delivery of Temozolomide using ultrasmall large-pore silica nanoparticles for glioblastoma

The prognosis of brain cancers such as glioblastoma remains poor despite numerous advancements in the field of neuro-oncology. The presence of the blood brain barrier (BBB) along with the highly invasive and aggressive nature of glioblastoma presents a difficult challenge for developing effective therapies. Temozolomide (TMZ) is a first line agent used in the clinic for glioblastoma and it has been useful in increasing patient survival rates. However, TMZ suffers from issues related to its pharmacokinetics, such as a short plasma half-life (2 h), is subjected to P-gp efflux, and has limited extravasation from blood to brain (~20%). It has been postulated that reducing its efflux and increasing TMZ exposure to glioblastoma tissue could prove useful in treating glioblastoma and preventing tumour recurrence. Herein, ultra-small, large pore silica nanoparticles (USLP) have been loaded with TMZ, surface PEGlyated to reduce efflux and decorated with the cascade targeting protein lactoferrin for efficient uptake across the BBB and into glioblastoma. Our results demonstrate that USLP improves permeability of BBB in vitro as evidenced using a transwell model which mimics endothelial tight junctions with permeation being enhanced using PEGylated particles. Data from TMZ loaded USLP in vitro transwell BBB model also suggests that the USLP formulations can significantly reduce the efflux ratio of TMZ. In vitro apoptosis studies on glioblastoma cell lines U87 and GL261 were conducted which showed an improvement in TMZ induced glioblastoma apoptosis with USLP formulations compared to pure TMZ. Finally, a proof-of-concept preclinical mouse study demonstrated that when given intravenously at 50 mg/kg, USLP particles showed accumulation in the brain within a few hours without any obvious pathophysiological changes in vital organs as assessed via histology. Overall, the data suggests our innovative delivery system is efficient in extravasation from blood and permeating the BBB and has potential to improve efficacy of TMZ in glioblastoma therapy.

Pharmacokinetics and Biodistribution of 89Zr-Miltuximab and Its Antibody Fragments as Glypican-1 Targeting Immuno-PET Agents in Glioblastoma

Glioblastoma (GBM) is the most aggressive form of primary brain cancer, accounting for about 85% of all primary central nervous system (CNS) tumors. With standard treatment strategies like surgery, radiation, and chemotherapy, the median survival time of patients with GBM is only 12-15 months from diagnosis. The poor prognosis of GBM is due to a very high tumor recurrence rate following initial treatment, indicating a dire need for improved diagnostic and therapeutic alternatives for this disease. Antibody-based immunotheranostics holds great promise in treating GBM, combining the theranostic applications of radioisotopes and target-specificity of antibodies. In this study, we developed and validated antibody-based positron emission tomography (PET) tracers targeting the heparan sulfate proteoglycan, glypican-1 (GPC-1), for noninvasive detection of disease using diagnostic molecular imaging. GPC-1 is overexpressed in multiple solid tumor types, including GBM, and is a promising biomarker for novel immunotheranostics. Here, we investigate zirconium-89 (⁸⁹Zr)-conjugated Miltuximab (a clinical stage anti-GPC-1 monoclonal antibody developed by GlyTherix, Ltd.) and engineered fragments for their potential as immuno-PET tracers to detect GPC-1^positive GBM tumors in preclinical models. We explore the effects of molecular size, avidity, and Fc-domain on the pharmacokinetics and biodistribution in vivo, by comparing in parallel the full-length antibody (Miltuximab), Fab'2, Fab, and single-chain variable fragment (scFv) formats. High radiolabeling efficiency (>95%) was demonstrated by all the formats and the stability post-radiolabeling was higher for larger constructs of Miltuximab and the Fab. Receptor-mediated internalization of all ⁸⁹Zr-labeled formats was observed in a human GBM cell line in vitro, while full-length Miltuximab demonstrated the highest tumor retention (5.7 ± 0.94% ID/g, day-9 postinjection (p.i.)) and overall better tumor-to-background ratios than the smaller Fc-less formats. Results from in vivo PET image quantification and ex vivo scintillation counting were highly correlated. Altogether, ⁸⁹Zr-DFO-Miltuximab appears to be an effective immuno-PET imaging agent for detecting GPC-1^positive tumors such as GBM and the current results support utility of the Fc containing whole mAb format over smaller antibody fragments for this target.

Self-cyclisation as a general and efficient platform for peptide and protein macrocyclisation

Macrocyclisation of proteins and peptides results in a remarkable increase in structural stability, making cyclic peptides and proteins of great interest in drug discovery-either directly as drug leads or as in the case of cyclised nanodiscs (cNDs), as tools for studies of trans-membrane receptors and membrane-active peptides. Various biological methods have been developed that are capable of yielding head-to-tail macrocyclised products. Recent advances in enzyme-catalysed macrocyclisation include discovery of new enzymes or design of new engineered enzymes. Here, we describe the engineering of a self-cyclising "autocyclase" protein, capable of performing a controllable unimolecular reaction for generation of cyclic biomolecules in high yield. We characterise the self-cyclisation reaction mechanism, and demonstrate how the unimolecular reaction path provides alternative avenues for addressing existing challenges in enzymatic cyclisation. We use the method to produce several notable cyclic peptides and proteins, demonstrating how autocyclases offer a simple, alternative way to access a vast diversity of macrocyclic biomolecules.

Probing the Biocompatibility and Immune Cell Association of Chiral, Water-Soluble, Bottlebrush Poly(2-oxazoline)s

Poly(2-oxazoline)s (POx) have received substantial attention as poly(ethylene glycol) (PEG) alternatives in the biomedical field due to their biocompatibility, high functionality, and ease of synthesis. While POx have demonstrated strong potential as biomaterial constituents, the larger family of poly(cyclic imino ether)s (PCIE) to which POx belongs remains widely underexplored. One highly interesting sub-class of PCIE is poly(2,4-disubstituted-2-oxazoline)s (PdOx), which bear an additional substituent on the backbone of the polymers' repeating units. This allows fine-tuning of the hydrophilic/hydrophobic balance and renders the PdOx chiral when enantiopure 2-oxazoline monomers are used. Herein, we synthesize new water-soluble (R-/S-/RS-) poly(oligo(2-ethyl-4-methyl-2-oxazoline) methacrylate) (P(OEtMeOxMA)) bottlebrushes and compare them to well-established PEtOx- and PEG-based bottlebrush controls in terms of their physical properties, hydrophilicity, and biological behavior. We reveal that the P(OEtMeOxMA) bottlebrushes show a lower critical solution temperature behavior at a physiologically relevant temperature (∼44 °C) and that the enantiopure (R-/S-) variants display a chiral secondary structure. Importantly, we demonstrate the biocompatibility of the chiral P(OEtMeOxMA) bottlebrushes through cellular association and mouse biodistribution studies and show that these systems display higher immune cell association and organ accumulation than the two control polymers. These novel materials possess properties that hold promise for applications in the field of nanomedicine and may be beneficial carriers for therapeutics that require enhanced cellular association and immune cell interaction.

Modulating Macrophage Clearance of Nanoparticles: Comparison of Small-Molecule and Biologic Drugs as Pharmacokinetic Modifiers of Soft Nanomaterials

Nanomedicines show benefits in overcoming the limitations of conventional drug delivery systems by reducing side effects, toxicity, and exhibiting enhanced pharmacokinetic (PK) profiles to improve the therapeutic window of small-molecule drugs. However, upon administration, many nanoparticles (NPs) prompt induction of host innate immune responses, which in combination with other clearance pathways such as renal and hepatic, eliminate up to 99% of the administered dose. Here, we explore a drug predosing strategy to transiently suppress the mononuclear phagocyte system (MPS), subsequently improving the PK profile and biological behaviors exhibited by a model NP system [hyperbranched polymers (HBPs)] in an immunocompetent mouse model. In vitro assays allowed the identification of five drug candidates that attenuated cellular association. Predosing of lead compounds chloroquine (CQ) and zoledronic acid (ZA) further showed increased HBP retention within the circulatory system of mice, as shown by both fluorescence imaging and positron emission tomography-computed tomography. Flow cytometric evaluation of spleen and liver tissue cells following intravenous administration further demonstrated that CQ and ZA significantly reduced HBP association with myeloid cells by 23 and 16%, respectively. The results of this study support the use of CQ to pharmacologically suppress the MPS to improve NP PKs.

Pre-targeting of polymeric nanomaterials to balance tumour accumulation and clearance

Pre-targeting of bispecific antibodies is probed to enhance tumour retention while limiting clearance of administered multifunctional branched PEGylated nanomedicines. The temporal influence of pre-targeting on polymer interaction with tumour cells and tissue is explored using in vitro assays through to preclinical validation.

Investigation of a Dual siRNA/Chemotherapy Delivery System for Breast Cancer Therapy

Multidrug resistance (MDR) is a problem that is often associated with a poor clinical outcome in chemotherapeutic cancer treatment. MDR may potentially be overcome by utilizing synergistic approaches, such as combining siRNA gene therapy and chemotherapy to target different mechanisms of apoptosis. In this study, a strategy is presented for developing multicomponent nanomedicines using orthogonal and compatible chemistries that lead to effective nanotherapeutics. Hyperbranched polymers were used as drug carriers that contained doxorubicin (DOX), attached via a pH-sensitive hydrazone linkage, and ataxia-telangiectasia mutated (ATM) siRNA, attached via a redox-sensitive disulfide group. This nanomedicine also contained cyanine 5 (Cy5) as a diagnostic tracer as well as in-house developed bispecific antibodies that allowed targeting of the epidermal growth factor receptor (EGFR) present on tumor tissue. Highly efficient coupling of siRNA was achieved with 80% of thiol end-groups on the hyperbranched polymer coupling with siRNA. This attachment was reversible, with the majority of siRNA released in vitro under reducing conditions as desired. In cellular studies, the nanomedicine exhibited increased DNA damage and cancer cell inhibition compared to the individual treatments. Moreover, the nanomedicine has great potential to suppress the metabolism of cancer cells including both mitochondrial respiration and glycolytic activity, with enhanced efficacy observed when targeted to the cell surface protein EGFR. Our findings indicated that co-delivery of ATM siRNA and DOX serves as a more efficient therapeutic avenue in cancer treatment than delivery of the single species and offers a potential route for synergistically enhanced gene therapy.

Antibody-Based Formats to Target Glioblastoma: Overcoming Barriers to Protein Drug Delivery

Glioblastoma (GB) is recognized as the most aggressive form of primary brain cancer. Despite advances in treatment strategies that include surgery, radiation, and chemotherapy, the median survival time (∼15 months) of patients with GB has not significantly improved. The poor prognosis of GB is also associated with a very high chance of tumor recurrence (∼90%), and current treatment measures have failed to address the complications associated with this disease. However, targeted therapies enabled through antibody engineering have shown promise in countering GB when used in combination with conventional approaches. Here, we discuss the challenges in conventional as well as future GB therapeutics and highlight some of the known advantages of using targeted biologics to overcome these impediments. We also review a broad range of potential alternative routes that could be used clinically to administer anti-GB biologics to the brain through evasion of its natural barriers.

Nanoparticle based medicines: approaches for evading and manipulating the mononuclear phagocyte system and potential for clinical translation

For decades, nanomedicines have been reported as a potential means to overcome the limitations of conventional drug delivery systems by reducing side effects, toxicity and the non-ideal pharmacokinetic behaviour typically exhibited by small molecule drugs. However, upon administration many nanoparticles prompt induction of host inflammatory responses due to recognition and uptake by macrophages, eliminating up to 95% of the administered dose. While significant advances in nanoparticle engineering and consequent therapeutic efficacy have been made, it is becoming clear that nanoparticle recognition by the mononuclear phagocyte system (MPS) poses an impassable junction in the current framework of nanoparticle development. Hence, this has negative consequences on the clinical translation of nanotechnology with respect to therapeutic efficacy, systemic toxicity and economic benefit. In order to improve the translation of nanomedicines from bench-to-bedside, there is a requirement to either modify nanomedicines in terms of how they interact with intrinsic processes in the body, or modulate the body to be more accommodating for nanomedicine treatments. Here we provide an overview of the current standard for design elements of nanoparticles, as well as factors to consider when producing nanomedicines that have minimal MPS-nanoparticle interactions; we explore this landscape across the cellular to tissue and organ levels. Further, rather than designing materials to suit the body, a growing research niche involves modulating biological responses to administered nanomaterials. We here discuss how developing strategic methods of MPS 'pre-conditioning' with small molecule or biological drugs, as well as implementing strategic dosing regimens, such as 'decoy' nanoparticles, is essential to increasing nanoparticle therapeutic efficacy. By adopting such a perspective, we hope to highlight the increasing trends in research dedicated to improving nanomedicine translation, and subsequently making a positive clinical impact.

Synthesis, characterisation and evaluation of hyperbranched N-(2-hydroxypropyl) methacrylamides for transport and delivery in pancreatic cell lines in vitro and in vivo

Hyperbranched polymers have many promising features for drug delivery, owing to their ease of synthesis, multiple functional group content, and potential for high drug loading with retention of solubility. Here we prepared hyperbranched N-(2-hydroxypropyl)methacrylamide (HPMA) polymers with a range of molar masses and particle sizes, and with attached dyes, radiolabel or the anticancer drug gemcitabine. Reversible addition-fragmentation chain transfer (RAFT) polymerisation enabled the synthesis of pHPMA polymers and a gemcitabine-comonomer functionalised pHPMA polymer pro-drug, with diameters of the polymer particles ranging from 7-40 nm. The non-drug loaded polymers were well-tolerated in cancer cell lines and macrophages, and were rapidly internalised in 2D cell culture and transported efficiently to the centre of dense pancreatic cancer 3D spheroids. The gemcitabine-loaded polymer pro-drug was found to be toxic both to 2D cultures of MIA PaCa-2 cells and also in reducing the volume of MIA PaCa-2 spheroids. The non-drug loaded polymers caused no short-term adverse effects in healthy mice following systemic injection, and derivatives of these polymers labelled with ⁸⁹Zr-were tracked for their distribution in the organs of healthy and MIA PaCa-2 xenograft bearing Balb/c nude mice. Tumour accumulation, although variable across the samples, was highest in individual animals for the pHPMA polymer of ∼20 nm size, and accordingly a gemcitabine pHPMA polymer pro-drug of ∼18 nm diameter was evaluated for efficacy in the tumour-bearing animals. The efficacy of the pHPMA polymer pro-drug was very similar to that of free gemcitabine in terms of tumour growth retardation, and although there was a survival benefit after 70 days for the polymer pro-drug, there was no difference at day 80. These data suggest that while polymer pro-drugs of this type can be effective, better tumour targeting and enhanced in situ release remain as key obstacles to clinical translation even for relatively simple polymers such as pHPMA.

Development of targeted micelles and polymersomes prepared from degradable RAFT-based diblock copolymers and their potential role as nanocarriers for chemotherapeutics

Modern polymerisation techniques allow synthesis of functional block copolymers that can self-assemble into degradable nanoparticles (NPs) of different sizes and conformations.

Evaluation of the in vivo fate of ultrapure alginate in a BALB/c mouse model

The linear anionic polysaccharide alginate (ALG) has been comprehensively studied for biomedical applications, yet thus far the in vivo fate of this polymer has not been explored in detail. The current study therefore evaluates the biodistribution of ultrapure ALG (M/G ratio ≥ 0.67 with a measured M_w of 530 kg/mol and polydispersity index; PDI of 1.49) over a 14-day period in BALB/c mice. The biodistribution pattern over 2-days after sample administration using PET imaging with ⁶⁴Cu-labelled ALG showed liver and spleen uptake. This was confirmed by the 14-day biodistribution profile of cyanine 5-labelled ALG from in vivo and ex vivo fluorescence imaging. Using MacGreen mice confirmed the uptake of the ALG by macrophages in the spleen at the 2-day time point. This extended biodistribution study confirmed the clearance of only a portion of the administered ALG biopolymer, but also uptake by macrophage populations in the spleen over a 14-day period.

Characterization of the Biodistribution of a Silica Vesicle Nanovaccine Carrying a Rhipicephalus (Boophilus) microplus Protective Antigen With in vivo Live Animal Imaging

Development of veterinary subunit vaccines comes with a spectrum of challenges, such as the choice of adjuvant, antigen delivery vehicle, and optimization of dosing strategy. Over the years, our laboratory has largely focused on investigating silica vesicles (SVs) for developing effective veterinary vaccines for multiple targets. Rhipicephalus microplus (cattle tick) are known to have a high impact on cattle health and the livestock industry in the tropical and subtropical regions. Development of vaccine using Bm86 antigen against R. microplus has emerged as an attractive alternative to control ticks. In this study, we have investigated the biodistribution of SV in a live animal model, as well as further explored the SV ability for vaccine development. Rhodamine-labeled SV-140-C₁₈ (Rho-SV-140-C₁₈) vesicles were used to adsorb the Cy5-labeled R. microplus Bm86 antigen (Cy5-Bm86) to enable detection and characterization of the biodistribution of SV as well as antigen in vivo in a small animal model for up to 28 days using optical fluorescence imaging. We tracked the in vivo biodistribution of SVs and Bm86 antigen at different timepoints (days 3, 8, 13, and 28) in BALB/c mice. The biodistribution analysis by live imaging as well as by measuring the fluorescent intensity of harvested organs over the duration of the experiment (28 days) showed greater accumulation of SVs at the site of injection. The Bm86 antigen biodistribution was traced in lymph nodes, kidney, and liver, contributing to our understanding how this delivery platform successfully elicits antibody responses in the groups administered antigen in combination with SV. Selected tissues (skin, lymph nodes, spleen, kidney, liver, and lungs) were examined for any cellular abnormalities by histological analysis. No adverse effect or any other abnormalities were observed in the tissues.

Engineering Fluorescent Gold Nanoclusters Using Xanthate-Functionalized Hydrophilic Polymers: Toward Enhanced Monodispersity and Stability

We introduce xanthate-functionalized poly(cyclic imino ethers)s (PCIEs), specifically poly(2-ethyl-2-oxazoline) and poly(2-ethyl-2-oxazine) given their stealth characteristics, as an attractive alternative to conventional thiol-based ligands for the synthesis of highly monodisperse and fluorescent gold nanoclusters (AuNCs). The xanthate in the PCIEs interacts with Au ions, acting as a well-controlled template for the direct formation of PCIE-AuNCs. This method yields red-emitting AuNCs with a narrow emission peak (λ_em = 645 nm), good quantum yield (4.3-4.8%), long fluorescence decay time (∼722-844 ns), and unprecedented product yield (>98%). The PCIE-AuNCs exhibit long-term colloidal stability, biocompatibility, and antifouling properties, enabling a prolonged blood circulation, lower nonspecific accumulation in major organs, and better renal clearance when compared with AuNCs without polymer coating. The advances made here in the synthesis of metal nanoclusters using xanthate-functionalized PCIEs could propel the production of highly monodisperse, biocompatible, and renally clearable nanoprobes in large-scale for different theranostic applications.

The Impact of Polymer Size and Cleavability on the Intravenous Pharmacokinetics of PEG-Based Hyperbranched Polymers in Rats

A better understanding of the impact of molecular size and linkers is important for PEG-based hyperbranched polymers (HBPs) intended as tailored drug delivery vehicles. This study aimed to evaluate the effects of crosslinker chemistry (cleavable disulphide versus non-cleavable ethylene glycol methacrylate (EGDMA) linkers) and molecular weight within the expected size range for efficient renal elimination (22 vs. 48 kDa) on the intravenous pharmacokinetic and biodistribution properties of 89Zr-labelled HBPs in rats. All HBPs showed similar plasma pharmacokinetics over 72 h, despite differences in linker chemistry and size. A larger proportion of HBP with the cleavable linker was eliminated via the urine and faeces compared to a similar-sized HBP with the non-cleavable linker, while size had no impact on the proportion of the dose excreted. The higher molecular weight HBPs accumulated in organs of the mononuclear phagocyte system (liver and spleen) more avidly than the smaller HBP. These results suggest that HBPs within the 22 to 48 kDa size range show no differences in plasma pharmacokinetics, but distinct patterns of organ biodistribution and elimination are evident.

Controlling the Biological Fate of Micellar Nanoparticles: Balancing Stealth and Targeting

Integrating nanomaterials with biological entities has led to the development of diagnostic tools and biotechnology-derived therapeutic products. However, to optimize the design of these hybrid bionanomaterials, it is essential to understand how controlling the biological interactions will influence desired outcomes. Ultimately, this knowledge will allow more rapid translation from the bench to the clinic. In this paper, we developed a micellar system that was assembled using modular antibody-polymer amphiphilic materials. The amphiphilic nature was established using either poly(ethylene glycol) (PEG) or a single-chain variable fragment (scFv) from an antibody as the hydrophile and a thermoresponsive polymer (poly(oligoethylene glycol) methyl ether methacrylate) as the hydrophobe. By varying the ratios of these components, a series of nanoparticles with different antibody content was self-assembled, where the surface presentation of targeting ligand was carefully controlled. In vitro and in vivo analysis of these systems identified a mismatch between the optimal targeting ligand density to achieve maximum cell association in vitro compared to tumor accumulation in vivo. For this system, we determined an optimum antibody density for both longer circulation and enhanced targeting to tumors that balanced stealthiness of the particle (to evade immune recognition as determined in both mouse models and in whole human blood) with enhanced accumulation achieved through receptor binding on tumor cells in solid tumors. This approach provides fundamental insights into how different antibody densities affect the interaction of designed nanoparticles with both target cells and immune cells, thereby offering a method to probe the intricate interplay between increased targeting efficiency and the subsequent immune response to nanoparticles.

Effect of Chain-End Chemistries on the Efficiency of Coupling Antibodies to Polymers Using Unnatural Amino Acids

Novel conjugates that incorporate strategies for increasing the therapeutic payload, such as targeted polymeric delivery vehicles, have great potential in overcoming limitations of conventional antibody therapies that often exhibit immunogenicity and limited drug loading. Click chemistry has significantly expanded the toolbox of effective strategies for developing hybrid polymer-biomolecule conjugates, however, effective systems require orthogonality between the polymer and biomolecule chemistries to achieve efficient coupling. Here, three cycloaddition-based strategies for antibody conjugation to polymeric carriers are explored and show that a purely radical-based method for polymer synthesis and subsequent biomolecule attachment has a trade-off between coupling efficiency of the antibody and the ability to synthesize polymers with controlled chemical properties. It is shown that careful consideration of both coupling chemistries as well as the potential effect of how this modulates the chemical properties of the polymer nanocarrier should be considered during the development of such systems. The strategies described offer insight into improving conjugate development for therapeutic and theranostic applications. In this system, polymerization using conventional and established reversible addition fragmentation chain transfer (RAFT) agents, followed by multiple post-modification steps, always leads to systems with more defined chemical architectures compared to strategies that utilize alkyne-functional RAFT agents.

Next-Generation Polymeric Nanomedicines for Oncology: Perspectives and Future Directions

Precision polymers as advanced nanomedicines represent an appealing approach for the treatment of otherwise untreatable malignancies. By taking advantage of unique nanomaterial properties and implementing judicious design strategies, polymeric nanomedicines are able to be produced that overcome many barriers to effective treatment. Current key research focus areas anticipated to produce the greatest impact in polymer applications in nanomedicine for oncology include new strategies to achieve "active" targeting, polymeric pro-drug activation, and combinatorial polymer drug delivery approaches in combination with enhanced understanding of complex bio-nano interactions. These approaches, both in isolation or combination, form the next generation of precision nanomedicines with significant anticipated future health outcomes. Of necessity, these approaches will combine an intimate understanding of biological interactions with advanced materials design. This perspectives piece aims to highlight emerging opportunities that promise to be game changers in the nanomedicine oncology field. Discussed herein are current and next generation polymeric nanomedicines with a focus towards structures that are, or could, undergo clinical translation as well as highlight key advances in the field.

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.

Direct Comparison of Poly(ethylene glycol) and Phosphorylcholine Drug-Loaded Nanoparticles In Vitro and In Vivo

Phosphorylcholine is known to repel the absorption of proteins onto surfaces, which can prevent the formation of a protein corona on the surface of nanoparticles. This can influence the fate of nanoparticles used for drug delivery. This material could therefore serve as an alternative to poly(ethylene glycol) (PEG). Herein, the synthesis of different particles prepared by polymerization-induced self-assembly (PISA) coated with either poly(ethylene glycol) (PEG) or zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) and 4-(N-(S-penicillaminylacetyl)amino) phenylarsenonous acid (PENAO) was reported. The anticancer drug 4-(N-(S-penicillaminylacetyl)amino) phenylarsenonous acid (PENAO) was conjugated to the shell-forming block. Interactions of the different coated nanoparticles, which present comparable sizes and size distributions (76-85 nm, PDI = 0.067-0.094), with two-dimensional (2D) and three-dimensional (3D) cultured cells were studied, and their cytotoxicities, cellular uptakes, spheroid penetration, and cell localization profiles were analyzed. While only a minimal difference in behaviour was observed for nanoparticles assessed using in vitro experiment (with PEG-co- PENAO-coated micelles showing slightly higher cytotoxicity and better spheroid penetration and cell localization ability), the effect of the different physicochemical properties between nanoparticles had a more dramatic effect on in vivo biodistribution. After 1 h of injection, the majority of the MPC-co-PENAO-coated nanoparticles were found to accumulate in the liver, making this particle system unfeasible for future biological studies.

Targeted beta therapy of prostate cancer with 177Lu-labelled Miltuximab® antibody against glypican-1 (GPC-1)

PURPOSE

Chimeric antibody Miltuximab®, a human IgG1 engineered from the parent antibody MIL-38, is in clinical development for solid tumour therapy. Miltuximab® targets glypican-1 (GPC-1), a cell surface protein involved in tumour growth, which is overexpressed in solid tumours, including prostate cancer (PCa). This study investigated the potential of ⁸⁹Zr-labelled Miltuximab® as an imaging agent, and ¹⁷⁷Lu-labelled Miltuximab® as a targeted beta therapy, in a mouse xenograft model of human prostate cancer.

METHODS

Male BALB/c nude mice were inoculated subcutaneously with GPC-1-positive DU-145 PCa cells. In imaging and biodistribution studies, mice bearing palpable tumours received (a) 2.62 MBq [⁸⁹Zr]Zr-DFO-Miltuximab® followed by PET-CT imaging, or (b) 6 MBq [¹⁷⁷Lu]Lu-DOTA-Miltuximab® by Cerenkov imaging, and ex vivo assessment of biodistribution. In an initial tumour efficacy study, mice bearing DU-145 tumours were administered intravenously with 6 MBq [¹⁷⁷Lu]Lu-DOTA-Miltuximab® or control DOTA-Miltuximab® then euthanised after 27 days. In a subsequent survival efficacy study, tumour-bearing mice were given 3 or 10 MBq of [¹⁷⁷Lu]Lu-DOTA-Miltuximab®, or control, and followed up to 120 days.

RESULTS

Antibody accumulation in DU-145 xenografts was detected by PET-CT imaging using [⁸⁹Zr]Zr-DFO-Miltuximab® and confirmed by Cerenkov luminescence imaging post injection of [¹⁷⁷Lu]Lu-DOTA-Miltuximab®. Antibody accumulation was higher (% IA/g) in tumours than other organs across multiple time points. A single injection with 6 MBq of [¹⁷⁷Lu]Lu-DOTA-Miltuximab® significantly inhibited tumour growth as compared with DOTA-Miltuximab® (control). In the survival study, mice treated with 10 MBq [¹⁷⁷Lu]Lu-DOTA-Miltuximab® had significantly prolonged survival (mean 85 days) versus control (45 days), an effect associated with increased cancer cell apoptosis. Tissue histopathology assessment showed no abnormalities associated with [¹⁷⁷Lu]Lu-DOTA-Miltuximab®, in line with other observations of tolerability, including body weight stability.

CONCLUSION

These findings demonstrate the potential utility of Miltuximab® as a PET imaging agent ([⁸⁹Zr]Zr-DFO-Miltuximab®) and a beta therapy ([¹⁷⁷Lu]Lu-DOTA-Miltuximab®) in patients with PCa or other GPC-1 expressing tumours.

Targeted and modular architectural polymers employing bioorthogonal chemistry for quantitative therapeutic delivery

There remain several key challenges to existing therapeutic systems for cancer therapy, such as quantitatively determining the true, tissue-specific drug release profile in vivo, as well as reducing side-effects for an increased standard of care. Hence, it is crucial to engineer new materials that allow for a better understanding of the in vivo pharmacokinetic/pharmacodynamic behaviours of therapeutics. We have expanded on recent “click-to-release” bioorthogonal pro-drug activation of antibody-drug conjugates (ADCs) to develop a modular and controlled theranostic system for quantitatively assessing site-specific drug activation and deposition from a nanocarrier molecule, by employing defined chemistries. The exploitation of quantitative imaging using positron emission tomography (PET) together with pre-targeted bioorthogonal chemistries in our system provided an effective means to assess in real-time the exact amount of active drug administered at precise sites in the animal; our methodology introduces flexibility in both the targeting and therapeutic components that is specific to nanomedicines and offers unique advantages over other technologies. In this approach, the in vivo click reaction facilitates pro-drug activation as well as provides a quantitative means to investigate the dynamic behaviour of the therapeutic agent.

There remain several key challenges to existing therapeutic systems for cancer therapy, such as quantitatively determining the true, tissue-specific drug release profile in vivo, as well as reducing side-effects for an increased standard of care.

Synthesis of biscarboxylic acid functionalised EDTA mimicking polymers and their ability to form Zr(iv) chelation mediated nanostructures

We present a new biscarboxylic acid acrylate, which is used for the synthesis of double hydrophilic EDTA-mimicking block copolymers capable of self-assembly upon zirconium complexation.

Polymer design and component selection contribute to uptake, distribution & trafficking behaviours of polyethylene glycol hyperbranched polymers in live MDA-MB-468 breast cancer cells

As polymeric nanomedicines grow increasingly complex in design, an effective therapeutic release is often inherently tied to localisation to specific intracellular compartments or microenvironments. The inclusion of environmentally-sensitive moieties links the functionality of such materials to the trafficking behaviours exhibited once materials have obtained access to the cellular milieu. In order to perform their designed function, such materials often need to encounter specific biological cues or stimuli. As such, there is an increased need to improve our understanding of how the physicochemical properties of nanomaterials influence post-internalisation behaviours. Amongst the unknown factors that may contribute to the trafficking behaviours and distribution of polymers within the cellular environment, is the influence of the components selected in the development of such materials. To examine whether composition and arrangement of components within small polymeric nanomaterials contribute to their ability to navigate the intracellular space, here we utilise fluorophores to model component selection, varying the fluorescent handle selected and its method of incorporation. We explore the intracellular behaviours of well-characterised hyperbranched polymers in live MDA-MB-468 breast cancer cells in vitro. Changes in distribution as a function of both fluorophore selection and placement are reported, and our data suggest that the individual components used to produce potential nanomedicines are critical to their overall functioning and efficacy. Further to this, through the use of a novel non-conjugated targeting ligand, we demonstrate that there is inherent competition between component-directing factors and cellular influences on the ultimate fate of the polymers. The behaviours reported here suggest that not only does component selection contribute to intracellular processing, but these factors could potentially be harnessed when designing polymers to ensure improved functionality of future materials for therapeutic delivery.

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.

Designed multifunctional polymeric nanomedicines: long-term biodistribution and tumour accumulation of aptamer-targeted nanomaterials

We report a novel multifunctional hyperbranched polymer based on polyethylene glycol (PEG) as a nanomedicine platform that facilitates longitudinal and quantitative 89Zr-PET imaging, enhancing knowledge of nanomaterial biodistribution and pharmacokinetics/pharmacodynamics both in vivo and ex vivo. Anti-VEGF-A DNA aptamer functionalization increased tumour accumulation by >2-fold in a breast cancer model.

In vivo therapeutic evaluation of polymeric nanomedicines: effect of different targeting peptides on therapeutic efficacy against breast cancer

Targeted nanomedicines offer many advantages over macromolecular therapeutics that rely only on passive accumulation within the tumour environment. The aim of this work was to investigate the in vivo anticancer efficiency of polymeric nanomedicines that were conjugated with peptide aptamers that show high affinity for receptors on many cancer cells. In order to assess the ability for the nanomedicine to treat cancer and investigate how structure affected the behavior of the nanomedicine, three imaging modalities were utilized, including in vivo optical imaging, multispectral optoacoustic tomography (MSOT) and ex vivo confocal microscopy. An 8-mer (A8) or 13-mer (A13) peptide aptamer that have been shown to exhibit high affinity for heat shock protein 70 (HSP70) was covalently-bound to hyperbranched polymer (HBP) nanoparticles with the purpose of both cellular targeting, as well as the potential to impart some level of chemo-sensitization to the cells. Furthermore, doxorubicin was bound to the polymeric carrier as the anticancer drug, and Cyanine-5.5 (Cy5.5) was incorporated into the polymer as a monomeric fluorophore to aid in monitoring the behavior of the nanomedicine. Enhanced tumour regression was observed in nude mice bearing MDA-MB-468 xenografts when the nanocarriers were targeted using the peptide ligands, compared to control groups treated with free DOX or HBP without aptamer. The accumulated DOX level in solid tumours was 5.5 times higher in mice treated with the targeted therapeutic, than mice treated with free DOX, and 2.6 times higher than the untargeted nanomedicine that relied only on passive accumulation. The results suggest that aptamer-targeted therapeutics have great potential for improving accumulation of nanomedicines in tumours for therapy.

Confinement of Therapeutic Enzymes in Selectively Permeable Polymer Vesicles by Polymerization-Induced Self-Assembly (PISA) Reduces Antibody Binding and Proteolytic Susceptibility

Covalent PEGylation of biologics has been widely employed to reduce immunogenicity, while improving stability and half-life in vivo. This approach requires covalent protein modification, creating a new entity. An alternative approach is stabilization by encapsulation into polymersomes; however this typically requires multiple steps, and the segregation requires the vesicles to be permeable to retain function. Herein, we demonstrate the one-pot synthesis of therapeutic enzyme-loaded vesicles with size-selective permeability using polymerization-induced self-assembly (PISA) enabling the encapsulated enzyme to function from within a confined domain. This strategy increased the proteolytic stability and reduced antibody recognition compared to the free protein or a PEGylated conjugate, thereby reducing potential dose frequency and the risk of immune response. Finally, the efficacy of encapsulated l-asparaginase (clinically used for leukemia treatment) against a cancer line was demonstrated, and its biodistribution and circulation behavior in vivo was compared to the free enzyme, highlighting this methodology as an attractive alternative to the covalent PEGylation of enzymes.

Modified Organosilica Core-Shell Nanoparticles for Stable pH Sensing in Biological Solutions

Continuous monitoring using nanoparticle-based sensors has been successfully employed in complex biological systems, yet the sensors still suffer from poor long-term stability partially because of the scaffold materials chosen to date. Organosilica core-shell nanoparticles containing a mixture of covalently incorporated pH-sensitive (shell) and pH-insensitive (core) fluorophores is presented as a continuous pH sensor for application in biological media. In contrast to previous studies focusing on similar materials, we sought to investigate the sensor characteristics (dynamic range, sensitivity, response time, stability) as a function of material properties. The ratio of the fluorescence intensities at specific wavelengths was found to be highly sensitive to pH over a physiologically relevant range (4.5-8) with a response time of <100 ms, significantly faster than that of previously reported response times using silica-based particles. Particles produced stable, pH-specific signals when stored at room temperature for more than 80 days. Finally, we demonstrated that the nanosensors successfully monitored the pH of a bacterial culture over 15 h and that pH changes in the skin of mouse cadavers could also be observed via in vivo fluorescence imaging following subcutaneous injection. The understanding gained from linking sensor characteristics and material properties will inform the next generation of optical nanosensors for continuous-monitoring applications.

Polynitroxide copolymers to reduce biofilm fouling on surfaces

Polynitroxide films – the first example of surface tethered nitroxides reducing biofilm fouling.

Gold Nanocluster-Mediated Cellular Death under Electromagnetic Radiation

Gold nanoclusters (Au NCs) have become a promising nanomaterial for cancer therapy because of their biocompatibility and fluorescent properties. In this study, the effect of ultrasmall protein-stabilized 2 nm Au NCs on six types of mammalian cells (fibroblasts, B-lymphocytes, glioblastoma, neuroblastoma, and two types of prostate cancer cells) under electromagnetic radiation is investigated. Cellular association of Au NCs in vitro is concentration-dependent, and Au NCs have low intrinsic toxicity. However, when Au NC-incubated cells are exposed to a 1 GHz electromagnetic field (microwave radiation), cell viability significantly decreases, thus demonstrating that Au NCs exhibit specific microwave-dependent cytotoxicity, likely resulting from localized heating. Upon i.v. injection in mice, Au NCs are still present at 24 h post administration. Considering the specific microwave-dependent cytotoxicity and low intrinsic toxicity, our work suggests the potential of Au NCs as effective and safe nanomedicines for cancer therapy.