Fibrin-binding, peptide amphiphile micelles for targeting glioblastoma

Targeting the undruggable in glioblastoma using nano-based intracellular drug delivery

Glioblastoma (GBM) is a highly prevalent and aggressive brain tumor in adults with limited treatment response, leading to a 5-year survival rate of less than 5%. Standard therapies, including surgery, radiation, and chemotherapy, often fall short due to the tumor's location, hypoxic conditions, and the challenge of complete removal. Moreover, brain metastases from cancers such as breast and melanoma carry similarly poor prognoses. Recent advancements in nanomedicine offer promising solutions for targeted GBM therapies, with nanoparticles (NPs) capable of delivering chemotherapy drugs or radiation sensitizers across the blood-brain barrier (BBB) to specific tumor sites. Leveraging the enhanced permeability and retention effect, NPs can preferentially accumulate in tumor tissues, where compromised BBB regions enhance delivery efficiency. By modifying NP characteristics such as size, shape, and surface charge, researchers have improved circulation times and cellular uptake, enhancing therapeutic efficacy. Recent studies show that combining photothermal therapy with magnetic hyperthermia using AuNPs and magnetic NPs induces ROS-dependent apoptosis and immunogenic cell death providing dual-targeted, immune-activating approaches. This review discusses the latest NP-based drug delivery strategies, including gene therapy, receptor-mediated transport, and multi-modal approaches like photothermal-magnetic hyperthermia combinations, all aimed at optimizing therapeutic outcomes for GBM.

Dual electro-/pH-responsive nanoparticle/hydrogel system for controlled delivery of anticancer peptide

An electro-chemo-responsive carrier has been engineered for the controlled release of a highly hydrophilic anticancer peptide, CR(NMe)EKA (Cys-Arg- N-methyl-Glu-Lys-Ala). Remotely controlled on demand release of CR(NMe)EKA, loaded in electro-responsive poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles, has been achieved by applying electrical stimuli consisting of constant positive (+0.50 V) or negative voltages (-0.50 V) at pre-defined time intervals. In addition, after loading CR(NMe)EKA/PEDOT nanoparticles into an injectable pH responsive hydrogel formed by phenylboronic acid grafted to chitosan (PBA-CS), the efficiency of the controlled peptide release has increased approximately by a factor of 2.6. The hydration ratio of such hydrogel is significantly lower in acidic environments than in neutral and basic media, which has been attributed to the dissociation of the boronate bonds between polymer chains. Hence, the electro-controlled peptide release from PBA-CS/CR(NMe)EKA/PEDOT hydrogels, in the acidic environment of tumors, combines the effects of the oxidation and reduction of PEDOT chains on the interactions with the peptide and the carrier, with the peptide concentration gradient at the interface between the collapsed hydrogel and the release medium. Furthermore, the peptide released by electro-stimulation preserved its bioactivity assessed by promoting human prostate cancer cells death. Overall, this work is a promising attempt to develop a carrier platform for small hydrophilic anticancer peptides, which delivery rationale is synergistically regulated by the electrical and pH responsiveness of the carrier.

Reprograming Clots for In Vivo Chemical Targeting in Traumatic Brain Injury

Traumatic brain injury (TBI) is a critical public health concern, yet there are no therapeutics available to improve long-term outcomes. Drug delivery to TBI remains a challenge due to the blood-brain barrier and increased intracranial pressure. In this work, a chemical targeting approach to improve delivery of materials to the injured brain, is developed. It is hypothesized that the provisional fibrin matrix can be harnessed as an injury-specific scaffold that can be targeted by materials via click chemistry. To accomplish this, the brain clot is engineered in situ by delivering fibrinogen modified with strained cyclooctyne (SCO) moieties, which incorporated into the injury lesion and is retained there for days. Improved intra-injury capture and retention of diverse, clickable azide-materials including a small molecule azide-dye, 40 kDa azide-PEG nanomaterial, and a therapeutic azide-protein in multiple dosing regimens is subsequently observed. To demonstrate therapeutic translation of this approach, a reduction in reactive oxygen species levels in the injured brain after delivery of the antioxidant catalase, is achieved. Further, colocalization between azide and SCO-fibrinogen is specific to the brain over off-target organs. Taken together, a chemical targeting strategy leveraging endogenous clot formation is established which can be applied to improve therapeutic delivery after TBI.

Oral delivery of nanomedicine for genetic kidney disease

Chronic and genetic kidney diseases such as autosomal dominant polycystic kidney disease (ADPKD) have few therapeutic options, and clinical trials testing small molecule drugs have been unfavorable due to low kidney bioavailability and adverse side effects. Although nanoparticles can be designed to deliver drugs directly to the diseased site, there are no kidney-targeted nanomedicines clinically available, and most FDA-approved nanoparticles are administered intravenously which is not ideal for chronic diseases. To meet these challenges of chronic diseases, we developed a biomaterials-based strategy using chitosan particles (CP) for oral delivery of therapeutic, kidney-targeting peptide amphiphile micelles (KMs). We hypothesized that encapsuling KMs into CP would enhance the bioavailability of KMs upon oral administration given the high stability of chitosan in acidic conditions and mucoadhesive properties enabling absorption within the intestines. To test this, we evaluated the mechanism of KM access to the kidneys via intravital imaging and investigated the KM biodistribution in a porcine model. Next, we loaded KMs carrying the ADPKD drug metformin into CP (KM-CP-met) and measured in vitro therapeutic effect. Upon oral administration in vivo, KM-CP-met showed significantly greater bioavailability and accumulation in the kidneys as compared to KM only or free drug. As such, KM-CP-met treatment in ADPKD mice (Pkd1fl/fl;Pax8-rtTA;Tet-O-Cre which develops the disease over 120 days and mimics the slow development of ADPKD) showed enhanced therapeutic efficacy without affecting safety despite repeated treatment. Herein, we demonstrate the potential of KM-CP as a nanomedicine strategy for oral delivery for the long-term treatment of chronic kidney diseases.

MRI Detection of Lymph Node Metastasis through Molecular Targeting of C-C Chemokine Receptor Type 2 and Monocyte Hitchhiking

Biopsy is the clinical standard for diagnosing lymph node (LN) metastasis, but it is invasive and poses significant risk to patient health. Magnetic resonance imaging (MRI) has been utilized as a noninvasive alternative but is limited by low sensitivity, with only ∼35% of LN metastases detected, as clinical contrast agents cannot discriminate between healthy and metastatic LNs due to nonspecific accumulation. Nanoparticles targeted to the C-C chemokine receptor 2 (CCR2), a biomarker highly expressed in metastatic LNs, have the potential to guide the delivery of contrast agents, improving the sensitivity of MRI. Additionally, cancer cells in metastatic LNs produce monocyte chemotactic protein 1 (MCP1), which binds to CCR2+ inflammatory monocytes and stimulates their migration. Thus, the molecular targeting of CCR2 may enable nanoparticle hitchhiking onto monocytes, providing an additional mechanism for metastatic LN targeting and early detection. Hence, we developed micelles incorporating gadolinium (Gd) and peptides derived from the CCR2-binding motif of MCP1 (MCP1-Gd) and evaluated the potential of MCP1-Gd to detect LN metastasis. When incubated with migrating monocytes in vitro, MCP1-Gd transport across lymphatic endothelium increased 2-fold relative to nontargeting controls. After administration into mouse models with initial LN metastasis and recurrent LN metastasis, MCP1-Gd detected metastatic LNs by increasing MRI signal by 30-50% relative to healthy LNs. Furthermore, LN targeting was dependent on monocyte hitchhiking, as monocyte depletion decreased accumulation by >70%. Herein, we present a nanoparticle contrast agent for MRI detection of LN metastasis mediated by CCR2-targeting and demonstrate the potential of monocyte hitchhiking for enhanced nanoparticle delivery.

Therapeutic Supramolecular Polymers: Designs and Applications

The self-assembly of low-molecular-weight building motifs into supramolecular polymers has unlocked a new realm of materials with distinct properties and tremendous potential for advancing medical practices. Leveraging the reversible and dynamic nature of non-covalent interactions, these supramolecular polymers exhibit inherent responsiveness to their microenvironment, physiological cues, and biomolecular signals, making them uniquely suited for diverse biomedical applications. In this review, we intend to explore the principles of design, synthesis methodologies, and strategic developments that underlie the creation of supramolecular polymers as carriers for therapeutics, contributing to the treatment and prevention of a spectrum of human diseases. We delve into the principles underlying monomer design, emphasizing the pivotal role of non-covalent interactions, directionality, and reversibility. Moreover, we explore the intricate balance between thermodynamics and kinetics in supramolecular polymerization, illuminating strategies for achieving controlled sizes and distributions. Categorically, we examine their exciting biomedical applications: individual polymers as discrete carriers for therapeutics, delving into their interactions with cells, and in vivo dynamics; and supramolecular polymeric hydrogels as injectable depots, with a focus on their roles in cancer immunotherapy, sustained drug release, and regenerative medicine. As the field continues to burgeon, harnessing the unique attributes of therapeutic supramolecular polymers holds the promise of transformative impacts across the biomedical landscape.

SREKA-targeted liposomes for highly metastatic breast cancer therapy

Chemotherapy is still a leading therapeutic approach in various tumor types that is often accompanied by a poor prognosis because of metastases. PEGylated liposomes with CREKA targeting moiety are well-known therapeutic agents, especially in highly metastatic experimental models. CREKA specifically targets tumor-associated ECM, which is present at the primary, as well as metastatic tumor sites. To better understand the function of the targeting moieties, we decided to design various liposome formulations with different amounts of targeting moiety attached to their DSPE-PEG molecules. Moreover, a new tumor-homing pentapeptide (SREKA) was designed, and a novel conjugation strategy between SREKA and DSPE-PEGs. First, the in vitro proliferation inhibition of drug-loaded liposomes and the cellular uptake of their cargo were investigated. Afterward, liposome stability in murine blood and drug accumulation in different tissues were measured. Furthermore, in vivo tumor growth, and metastasis inhibition potencies of the different liposome formulations were examined. According to our comparative studies, SREKA-liposomes have a uniform phenotype after formulation and have similar characteristics and tumor-homing capabilities to CREKA-liposomes. However, the exchange of the N-terminal cysteine to serine during conjugation results in a higher production yield and better stability upon conjugation to DSPE-PEGs. We also showed that SREKA-liposomes have significant inhibition on primary tumor growth and metastasis incidence; furthermore, increase the survival rate of tumor-bearing mice. Besides, we provide evidence that the amount of targeting moiety attached to DSPE-PEGs is largely responsible for the stability of liposomes, therefore it plays an important role in toxicity and targeting.

Long-term, in vivo therapeutic effects of a single dose of miR-145 micelles for atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is characterized by the build-up of lipid-rich plaques in the arterial walls. The standard treatment for patients with atherosclerosis is statin therapy aimed to lower serum lipid levels. Despite its widespread use, many patients taking statins continue to experience acute events. Thus, to develop improved and alternative therapies, we previously reported on microRNA-145 (miR-145 micelles) and its ability to inhibit atherosclerosis by targeting vascular smooth muscle cells (VSMCs). Importantly, one dose of miR-145 micelles significantly abrogated disease progression when evaluated two weeks post-administration. Thus, in this study, to evaluate how long the sustained effects of miR-145 micelles can be maintained and towards identifying a dosing regimen that is practical for patients with chronic disease, the therapeutic effects of a single dose of miR-145 micelles were evaluated for up to two months in vivo. After one and two months post-treatment, miR-145 micelles were found to reduce plaque size and overall lesion area compared to all other controls including statins without causing adverse effects. Furthermore, a single dose of miR-145 micelle treatment inhibited VSMC transdifferentiation into pathogenic macrophage-like and osteogenic cells in plaques. Together, our data shows the long-term efficacy and sustained effects of miR-145 micelles that is amenable using a dosing frequency relevant to chronic disease patients.

Rational design of a glycopeptide probe system based on a reconfigurable immune microenvironment

Glioma is a highly challenging human malignancy and conventional drugs typically exhibit low blood-brain barrier (BBB) permeability as well as poor tumor targeting. To complicate matters further, recent advances in research on oncology have highlighted the dynamic and complex cellular networks within the immunosuppressive tumor microenvironment (TME) that complicate glioma treatment. Therefore, precise and efficient targeting of tumor tissue, whilst reversing immunosuppression, may provide an ideal strategy for the treatment of gliomas. Here, by using the "one-bead-one-component" combinatorial chemistry approach, we designed and screened a peptide that can specifically target brain glioma stem cells (GSCs), which was further engineered into glycopeptide-functionalized multifunctional micelles. We demonstrated that the micelles can carry DOX and effectively penetrate the BBB to achieve targeted killing of glioma cells. Meanwhile, mannose confers a unique tumor immune microenvironment modulating function to the micelles, which can activate the anti-tumor immune response function of tumor-associated macrophages and is expected to be further applied in vivo. This study highlights that glycosylation modification of targeted peptides specific to cancer stem cells (CSCs) may serve as an effective tool to improve the therapeutic outcome of brain tumor patients.

Current status of Cancer Nanotheranostics: Emerging strategies for cancer management

Cancer diagnosis and management have been a slow-evolving area in medical science. Conventional therapies have by far proved to have various limitations. Also, the concept of immunotherapy which was thought to revolutionize the management of cancer has presented its range of drawbacks. To overcome these limitations nanoparticulate-derived diagnostic and therapeutic strategies are emerging. These nanomaterials are to be explored as they serve as a prospect for cancer theranostics. Nanoparticles have a significant yet unclear role in screening as well as therapy of cancer. However, nanogels and Photodynamic therapy is one such approach to be developed in cancer theranostics. Photoactive cancer theranostics is a vivid area that might prove to help manage cancer. Also, the utilization of the quantum dots as a diagnostic tool and to selectively kill cancer cells, especially in CNS tumors. Additionally, the redox-sensitive micelles targeting the tumor microenvironment of the cancer are also an important theranostic tool. This review focuses on exploring various agents that are currently being studied or can further be studied as cancer theranostics.

Biomimetic nanoparticles directly remodel immunosuppressive microenvironment for boosting glioblastoma immunotherapy

Glioblastoma (GBM), as a very aggressive cancer of central nervous system, is very challenging to completely cure by the conventional combination of surgical resection with radiotherapy and chemotherapy. The success of emerging immunotherapy in hot tumors has attracted considerable interest for the treatment of GBM, but the unique tumor immunosuppressive microenvironment (TIME) of GBM leads to the failure of immunotherapy. Here, we show the significant improvement of the immunotherapy efficacy of GBM by modulating the TIME through novel all-in-one biomimetic nanoparticles (i.e. CS-I/J@CM NPs). The nanoparticles consist of utrasmall Cu_2-x Se nanoparticles (NPs) with outstanding intrinsic properties (e.g., photo-responsive Fenton-like catalytic property for inducing immunogenic cell death (ICD) and alleviating the hypoxia of tumor), indoximod (IND, an inhibitor of indoleamine-2,3-dioxygenease in tumor), JQ1 (an inhibitor for reducing the expression of PD-L1 by tumor cells), and tumor cell membrane for improving the targeting capability and accumulation of nanoparticles in tumor. We reveal that these smart CS-I/J@CM NPs could drastically activate the immune responses through remodeling TIME of GBM by multiple functions. They could (1) increase M1-phenotype macrophages at tumor site by promoting the polarization of tumor-associated macrophages through the reactive oxygen species (ROS) and oxygen generated from the Fenton-like reaction between nanoparticles and H₂O₂ within tumor under NIR II irradiation; (2) decrease the infiltration of Tregs cells at tumor site through the release of IND; (3) decrease the expression of PD-L1 on tumor cells through JQ1. The notable increments of anti-tumor CD8⁺T cells in the tumor and memory T cells (T_EM) in the spleen show excellent therapy efficacy and effectively prevent the recurrence of GBM after modulation of the TIME. This work demonstrates the modulation of TIME could be a significant strategy to improve the immunotherapy of GBM and other cold tumors.

Controlled Recognition and Corona Formation by Cascade Micellar Nanoprobes: for Boosting Glioma Theranostics

Both tumor-cell-targeting and BBB (blood-brain barrier)-penetrating ability are the key characteristics for glioma theranostics. We established one type of nanomicellar probe functionalized with a newly developed peptide WES. The micellar system could enact a series of cascaded functions in living bodies. It could specifically recruit the ApoE corona in blood circulation rather than perform nonspecific protein absorption. Following, it could penetrate into the BBB in an active manner. Finally, and most importantly, it could recognize and target the tumor marker as well as deliver drugs effectively toward glioma. The cascaded micellar system has shown satisfactory therapeutic ability for glioma in both a subcutaneous and orthotopic model, which provides a prospective strategy for brain cancer treatment.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Therapeutic Response of miR-145 Micelles on Patient-Derived Vascular Smooth Muscle Cells

During atherosclerosis, vascular smooth muscle cells (VSMCs) undergo a phenotypic transition from a healthy contractile state into pathological phenotypes including a proliferative and migratory, synthetic phenotype and osteochondrogenic-like phenotype that exacerbate plaques. Thus, inhibiting the transition of healthy, quiescent VSMCs to atherogenic cell types has the potential to mitigate atherosclerosis. To that end, previously, we reported that delivery of microRNA-145 (miR-145, a potent gatekeeper of the contractile VSMC phenotype) using nanoparticle micelles limited atherosclerotic plaque growth in murine models of atherosclerosis. Building on this preclinical data and toward clinical application, in this study, we tested the therapeutic viability of miR-145 micelles on patient-derived VSMCs and evaluated their effects based on disease severity. We collected vascular tissues from 11 patients with healthy, moderate, or severe stages of atherosclerosis that were discarded following vascular surgery or organ transplant, and isolated VSMCs from these tissues. We found that with increasing disease severity, patient-derived VSMCs had decreasing levels of contractile markers (miR-145, ACTA2, MYH11) and increasing levels of synthetic markers (KLF4, KLF5, and ELK1). Treatment with miR-145 micelles showed that an increase in disease severity correlated with a more robust response to therapy in VSMCs. Notably, miR-145 micelle therapy rescued contractile marker expression to baseline contractile levels in VSMCs derived from the most severely diseased tissues. As such, we demonstrate the use of miR-145 micelles across different stages of atherosclerosis disease and present further evidence of the translatability of miR-145 micelle treatment for atherosclerosis.

Vasoactive Intestinal Peptide Amphiphile Micelle Chemical Structure and Hydrophobic Domain Influence Immunomodulatory Potentiation

Vasoactive intestinal peptide (VIP) is a neuropeptide capable of downregulating innate immune responses in antigen presenting cells (APCs) by suppressing their pro-inflammatory cytokine secretion and cell surface marker expression. Though VIP's bioactivity could possibly be leveraged as a treatment for transplant tolerance, drug delivery innovation is required to overcome its intrinsically limited cellular delivery capacity. One option is to employ peptide amphiphiles (PAs) which are lipidated peptides capable of self-assembling into micelles in water that can enhance cellular association. With this approach in mind, a series of triblock VIP amphiphiles (VIPAs) has been synthesized to explore the influence of block arrangement and hydrophobicity on micelle biocompatibility and bioactivity. VIPA formulation has been found to influence the shape, size, and surface charge of VIPA micelles (VIPAMs) as well as their cytotoxicity and immunomodulatory effects. Specifically, the enclosed work provides strong evidence that cylindrical VIPAMs with aspect ratios of 1.5-150 and moderate positive surface charge are able to potentiate the bioactivity of VIP limiting TNF-α secretion and MHC II and CD86 surface expression on APCs. With these criteria, we have identified PalmK-(EK)₄-VIP as our lead formulation, which showed comparable or enhanced anti-inflammatory effects relative to the unmodified VIP at all dosages evaluated. Additionally, the relationships between peptide block location and lipid block size provide further information on the chemical structure-function relationships of PA micelles for the delivery of VIP as well as potentially for other peptides more broadly.

Stimuli-responsive, dual-function prodrug encapsulated in hyaluronic acid micelles to overcome doxorubicin resistance

Multidrug resistance (MDR) is the main challenge faced by cancer chemotherapy. Drug-conjugate offers a promising strategy for breast cancer therapy. In this regard, we developed a DNVM multifunctional drug delivery system by crosslinking doxorubicin (DOX) and vitamin E succinate (VES) with a pH-sensitive hydrazone bond and then encapsulated the DOX-NN-VES prodrug into pH-sensitive hyaluronic acid-2-(octadecyloxy)-1,3-dioxan-5-amine (HOD) micelles. DOX resistant MCF-7/ADR cell were adopted as a model to study the capability and mechanism of MDR reversal. DNVM exhibited much higher cytotoxicity and cell uptake efficiency compared with that of acid-insensitive DOX-VES loaded HOD micelles (DVSM) and DOX loaded HOD micelles (DOXM), indicating the better capacity of DNVM for the reversal of MDR. Moreover, DNVM prevented drug efflux more effectively, inhibited the expression of P-gp, induced excessive production of reactive oxygen species and affected the expression of apoptosis-related proteins. In vivo experiments showed that DNVM significantly inhibited the tumor growth with no obvious changes in the body weight of MCF-7/ADR cells-bearing nude mice. The results suggested that the "double gain" DNVM can synergistically enhance the efficacy of chemotherapeutics for DOX resistant tumor cells and has the potential to overcome tumor MDR. STATEMENT OF SIGNIFICANCE: A dual-functional pH-sensitive doxorubicin - vitamin E succinate prodrug was developed and loaded into tumor microenvironment-sensitive hyaluronic acid-2-(octadecyloxy)-1,3-dioxan-5-amine micelle system (DNVM) for sequencing stimuli-release and overcoming doxorubicin resistance. The "double gain" DNVM can synergistically enhance the efficacy of chemotherapeutics for doxorubicin resistant tumor cells and has the potential to overcome tumor multiple drug resistance.

Nanoscale Drug Delivery Systems in Glioblastoma

Glioblastoma is the most aggressive cerebral tumor in adults. However, the current pharmaceuticals in GBM treatment are mainly restricted to few chemotherapeutic drugs and have limited efficacy. Therefore, various nanoscale biomaterials that possess distinct structure and unique property were constructed as vehicles to precisely deliver molecules with potential therapeutic effect. In this review, nanoparticle drug delivery systems including CNTs, GBNs, C-dots, MOFs, Liposomes, MSNs, GNPs, PMs, Dendrimers and Nanogel were exemplified. The advantages and disadvantages of these nanoparticles in GBM treatment were illustrated.

Multifunctional polymeric micellar nanomedicine in the diagnosis and treatment of cancer

Polymeric micelles are a prevalent topic of research for the past decade, especially concerning their fitting ability to deliver drug and diagnostic agents. This delivery system offers outstanding advantages, such as biocompatibility, high loading efficiency, water-solubility, and good stability in biological fluids, to name a few. The multifunctional polymeric micellar architect offers the added capability to adapt its surface to meet the looked-for clinical needs. This review cross-talks the recent reports, proof-of-concept studies, patents, and clinical trials that utilize polymeric micellar family architectures concerning cancer targeted delivery of anticancer drugs, gene therapeutics, and diagnostic agents. The manuscript also expounds on the underlying opportunities, allied challenges, and ways to resolve their bench-to-bedside translation for allied clinical applications.

Peptides-based therapy and diagnosis. Strategies for non-invasive therapies in cancer

In recent years, remarkable progress was registered in the field of cancer research. Though, cancer still represents a major cause of death and cancer metastasis a problem seeking for urgent solutions as it is the main reason for therapeutic failure. Unfortunately, the most common chemotherapeutic agents are non-selective and can damage healthy tissues and cause side effects that affect dramatically the quality of life of the patients. Targeted therapy with molecules that act specifically at the tumour sites interacting with overexpressed cancer receptors is a very promising strategy for achieving the specific delivery of anticancer drugs, radioisotopes or imaging agents. This review aims to give an overview on different strategies for targeting cancer cell receptors localised either at the extracellular matrix or at the cell membrane. Molecules like antibodies, aptamers and peptides targeting the cell surface are presented with advantages and disadvantages, with emphasis on peptides. The most representative peptides are described, including cell penetrating peptides, homing and anticancer peptides with particular consideration on recent discoveries.

Harnessing Peptide Binding to Capture and Reclaim Phosphate

With rising consumer demands, society is tapping into wastewater as an innovative source to recycle depleting resources. Novel reclamation technologies have been recently explored for this purpose, including several that optimize natural biological processes for targeted reclamation. However, this emerging field has a noticeable dearth of synthetic material technologies that are programmed to capture, release, and recycle specified targets; and of the novel materials that do exist, synthetic platforms incorporating biologically inspired mechanisms are rare. We present here a prototype of a materials platform utilizing peptide amphiphiles that has been molecularly engineered to sequester, release, and reclaim phosphate through a stimuli-responsive pH trigger, exploiting a protein-inspired binding mechanism that is incorporated directly into the self-assembled material network. This material is able to harvest and controllably release phosphate for multiple cycles of reuse, and it is selective over nitrate and nitrite. We have determined by simulations that the binding conformation of the peptide becomes constrained in the dense micelle corona at high pH such that phosphate is expelled when it otherwise would be preferentially bound. However, at neutral pH, this dense structure conversely employs multichain binding to further stabilize phosphate when it would otherwise be unbound, opening opportunities for higher-order conformational binding design to be engineered into this controllably packed corona. With this work, we are pioneering a new platform to be readily altered to capture other valuable targets, presenting a new class of capture and release materials for recycling resources on the nanoscale.

Co-delivery of EGFR and BRD4 siRNA by cell-penetrating peptides-modified redox-responsive complex in triple negative breast cancer cells

AIMS

Triple negative breast cancer (TNBC) has drawn more and more attention due to its high mitotic indices, high metastatic rate and poor prognosis. Gene therapy, especially RNA interference (RNAi), has become a promising targeted therapy. However, improvement of transfection efficiency and discovery of target genes are major problems for the delivery of small interfering RNAs (siRNA).

MATERIALS AND METHODS

In the present study, we developed GALA- and CREKA-modified PEG-SS-PEI to deliver siRNAs targeting on EGFR and BRD4 for TNBC therapy. The PEG-SS-PEI/siRNA complexes were prepared by electrostatic interaction and characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). The release characteristic, stability, cellular uptake and intracellular localization of the complexes were also studied. The effect of the complexes on cell viability was measured in MDA-MB-231 and HUVEC cells. The in vitro anti-tumor activities of the complexes were analyzed by Transwell invasion assay and wound healing assay. The gene silencing effect was evaluated by quantitative real time-polymerase chain reaction (qRT-PCR) and western blot.

KEY FINDINGS

The results revealed that the GALA- and CREKA-modified PEG-SS-PEI/siRNA complexes showed excellent transfection efficiency with redox-sensitive release profile and good biological compatibility. The complexes protected siRNA from the degradation of RNA enzymes. The complexes significantly inhibited the proliferation, invasion and migration of MDA-MB-231 cells via the synergistic inhibition of EGFR/PI3K/Akt and BRD4/c-Myc pathways.

SIGNIFICANCE

Taken together, co-delivery of siEGFR and siBRD4 by GALA-PEG-SS-PEI and CREKA-PEG-SS-PEI may provide a more effective strategy for the treatment of TNBC.

Vascular-targeted micelles as a specific MRI contrast agent for molecular imaging of fibrin clots and cancer cells

Molecular medical imaging is intended to increase the accuracy of diagnosis, particularly in cardiovascular and cancer-related diseases, where early detection could significantly increase the treatment success rate. In this study, we present mixed micelles formed from four building blocks as a magnetic resonance imaging targeted contrast agent for the detection of atheroma and cancer cells. The building blocks are a gadolinium-loaded DOTA ring responsible for contrast enhancement, a fibrin-specific CREKA pentapeptide responsible for targeting, a fluorescent dye and DSPE-PEG₂₀₀₀. The micelles were fully characterized in terms of their size, zeta potential, stability, relaxivity and toxicity. Target binding assays performed on fibrin clots were quantified by fluorescence and image signal intensities and proved the binding power. An additional internalization assay showed that the micelles were also designed to specifically enter into cancer cells. Overall, these multimodal mixed micelles represent a potential formulation for MRI molecular imaging of atheroma and cancer cells.

Subacute melamine exposure disrupts task-based hippocampal information flow via inhibiting the subunits 2 and 3 of AMPA glutamate receptors expression

Although melamine exposure induces cognitive deficits and dysfunctional neurotransmission in hippocampal Cornus Ammonis (CA) 1 region of rats, it is unclear whether the neural function, such as neural oscillations between hippocampal CA3-CA1 pathway and postsynaptic receptors involves in these effects. The levels of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) subunit glutamate receptor (GluR) 1 and GluR2/3 in CA1 region of melamine-treated rats, which were intragastric treated with 300 mg/kg/day for 4 weeks, were detected. Following systemic or intra-hippocampal CA1 injection with GluR2/3 agonist, spatial learning of melamine-treated rats was assessed in Morris water maze (MWM) task. Local field potentials were recorded in CA3-CA1 pathway before and during behavioral test. General Partial Directed Coherence approach was applied to determine directionality of neural information flow between CA3 and CA1 regions. Results showed that melamine exposure reduced GluR2/3 but not GluR1 level and systemic or intra-hippocampal CA1 injection with GluR2/3 agonist effectively mitigated the learning deficits. Phase synchronization between CA3 and CA1 regions were significantly diminished in delta, theta and alpha oscillations. Coupling directional index and strength of CA3 driving CA1 were marked reduced as well. Intra-hippocampal CA1 infusion with GluR2/3 agonist significantly enhanced the phase locked value and reversed the melamine-induced reduction in the neural information flow (NIF) from CA3 to CA1 region. These findings support that melamine exposure decrease the expression of GluR2/3 subunit involved in weakening directionality index of NIF, and thereby induced spatial learning deficits.

Designing peptide nanoparticles for efficient brain delivery

The targeted delivery of therapeutic compounds to the brain is arguably the most significant open problem in drug delivery today. Nanoparticles (NPs) based on peptides and designed using the emerging principles of molecular engineering show enormous promise in overcoming many of the barriers to brain delivery faced by NPs made of more traditional materials. However, shortcomings in our understanding of peptide self-assembly and blood-brain barrier (BBB) transport mechanisms pose significant obstacles to progress in this area. In this review, we discuss recent work in engineering peptide nanocarriers for the delivery of therapeutic compounds to the brain: from synthesis, to self-assembly, to in vivo studies, as well as discussing in detail the biological hurdles that a nanoparticle must overcome to reach the brain.

CCR2-targeted micelles for anti-cancer peptide delivery and immune stimulation

Signaling between the CC chemokine receptor 2 (CCR2) with its ligand, monocyte chemoattractant protein-1 (MCP-1) promotes cancer progression by directly stimulating tumor cell proliferation and downregulating the expression of apoptotic proteins. Additionally, the MCP-1/CCR2 signaling axis drives the migration of circulating monocytes into the tumor microenvironment, where they mature into tumor-associated macrophages (TAMs) that promote disease progression through induction of angiogenesis, tissue remodeling, and suppression of the cytotoxic T lymphocyte (CTL) response. In order to simultaneously disrupt MCP-1/CCR2 signaling and target CCR2-expressing cancer cells for drug delivery, KLAK-MCP-1 micelles consisting of a CCR2-targeting peptide sequence (MCP-1 peptide) and the apoptotic KLAKLAK peptide were synthesized. In vitro, KLAK-MCP-1 micelles were observed to bind and induce cytotoxicity to cancer cells through interaction with CCR2. In vivo, KLAK-MCP-1 micelles inhibited tumor growth (34 ± 11%) in a subcutaneous B16F10 murine melanoma model despite minimal tumor accumulation upon intravenous injection. Tumors treated with KLAK-MCP1 demonstrated reduced intratumor CCR2 expression and altered infiltration of TAMs and CTLs as evidenced by immunohistochemical and flow cytometric analysis. These studies highlight the potential application of CCR2-targeted nanotherapeutic micelles in cancer treatment.

Transdermal Delivery of Kidney-Targeting Nanoparticles Using Dissolvable Microneedles

INTRODUCTION

Chronic kidney disease (CKD) affects approximately 13% of the world's population and will lead to dialysis or kidney transplantation. Unfortunately, clinically available drugs for CKD show limited efficacy and toxic extrarenal side effects. Hence, there is a need to develop targeted delivery systems with enhanced kidney specificity that can also be combined with a patient-compliant administration route for such patients that need extended treatment. Towards this goal, kidney-targeted nanoparticles administered through transdermal microneedles (KNP/MN) is explored in this study.

METHODS

A KNP/MN patch was developed by incorporating folate-conjugated micelle nanoparticles into polyvinyl alcohol MN patches. Rhodamine B (RhB) was encapsulated into KNP as a model drug and evaluated for biocompatibility and binding with human renal epithelial cells. For MN, skin penetration efficiency was assessed using a Parafilm model, and penetration was imaged via scanning electron microscopy. In vivo, KNP/MN patches were applied on the backs of C57BL/6 wild type mice and biodistribution, organ morphology, and kidney function assessed.

RESULTS

KNP showed high biocompatibility and folate-dependent binding in vitro, validating KNP's targeting to folate receptors in vitro. Upon transdermal administration in vivo, KNP/MN patches dissolved within 30 min. At varying time points up to 48 h post-KNP/MN administration, higher accumulation of KNP was found in kidneys compared with MN that consisted of the non-targeting, control-NP. Histological evaluation demonstrated no signs of tissue damage, and kidney function markers, serum blood urea nitrogen and urine creatinine, were found to be within normal ranges, indicating preservation of kidney health.

CONCLUSIONS

Our studies show potential of KNP/MN patches as a non-invasive, self-administrable platform to direct therapies to the kidneys.

The effect of size, charge, and peptide ligand length on kidney targeting by small, organic nanoparticles

Chronic kidney disease (CKD) affects 15% of the US adult population. However, most clinically available drugs for CKD show low bioavailability to the kidneys and non-specific uptake by other organs which results in adverse side effects. Hence, a targeted, drug delivery strategy to enhance kidney drug delivery is highly desired. Recently, our group developed small, organic nanoparticles called peptide amphiphile micelles (PAM) functionalized with the zwitterionic peptide ligand, (KKEEE)3K, that passage through the glomerular filtration barrier for kidney accumulation. Despite high bioavailability to the kidneys, these micelles also accumulated in the liver to a similar extent. To further optimize the physicochemical properties and develop design rules for kidney-targeting micelles, we synthesized a library of PAMs of varying size, charge, and peptide repeats. Specifically, variations of the original (KKEEE)3K peptide including (KKEEE)2K, (KKEEE)K, (EEKKK)3E, (EEKKK)2E, (EEKKK)E, KKKKK, and EEEEE were functionalized onto nanoparticles, and peptide surface density and PEG linker molecular weight were altered. After characterization with transmission electron microscopy (TEM) and dynamic light scattering (DLS), nanoparticles were intravenously administered into wildtype mice, and biodistribution was assessed through ex vivo imaging. All micelles localized to the kidneys, but nanoparticles that are positively-charged, close to the renal filtration size cut-off, and consisted of additional zwitterionic peptide sequences generally showed higher renal accumulation. Upon immunohistochemistry, micelles were confirmed to bind to the multiligand receptor, megalin, and histological analyses showed no tissue damage. Our study provides insight into the design of micelle carriers for kidney targeting and their potential for future therapeutic application.

Peptide-Based Nanoassemblies in Gene Therapy and Diagnosis: Paving the Way for Clinical Application

Nanotechnology approaches play an important role in developing novel and efficient carriers for biomedical applications. Peptides are particularly appealing to generate such nanocarriers because they can be rationally designed to serve as building blocks for self-assembling nanoscale structures with great potential as therapeutic or diagnostic delivery vehicles. In this review, we describe peptide-based nanoassemblies and highlight features that make them particularly attractive for the delivery of nucleic acids to host cells or improve the specificity and sensitivity of probes in diagnostic imaging. We outline the current state in the design of peptides and peptide-conjugates and the paradigms of their self-assembly into well-defined nanostructures, as well as the co-assembly of nucleic acids to form less structured nanoparticles. Various recent examples of engineered peptides and peptide-conjugates promoting self-assembly and providing the structures with wanted functionalities are presented. The advantages of peptides are not only their biocompatibility and biodegradability, but the possibility of sheer limitless combinations and modifications of amino acid residues to induce the assembly of modular, multiplexed delivery systems. Moreover, functions that nature encoded in peptides, such as their ability to target molecular recognition sites, can be emulated repeatedly in nanoassemblies. Finally, we present recent examples where self-assembled peptide-based assemblies with "smart" activity are used in vivo. Gene delivery and diagnostic imaging in mouse tumor models exemplify the great potential of peptide nanoassemblies for future clinical applications.

Ligand-Installed Nanocarriers toward Precision Therapy

Development of drug-delivery systems that selectively target neoplastic cells has been a major goal of nanomedicine. One major strategy for achieving this milestone is to install ligands on the surface of nanocarriers to enhance delivery to target tissues, as well as to enhance internalization of nanocarriers by target cells, which improves accuracy, efficacy, and ultimately enhances patient outcomes. Herein, recent advances regarding the development of ligand-installed nanocarriers are introduced and the effect of their design on biological performance is discussed. Besides academic achievements, progress on ligand-installed nanocarriers in clinical trials is presented, along with the challenges faced by these formulations. Lastly, the future perspectives of ligand-installed nanocarriers are discussed, with particular emphasis on their potential for emerging precision therapies.

Collagenase-Cleavable Peptide Amphiphile Micelles as a Novel Theranostic Strategy in Atherosclerosis

Atherosclerosis is an inflammatory disease characterized by plaques that can cause sudden myocardial infarction upon rupture. Such rupture-prone plaques have thin fibrous caps due to collagenase degradation, and a noninvasive diagnostic tool and targeted therapy that can identify and treat vulnerable plaques and may inhibit the onset of acute cardiac events. Toward this goal, monocyte-binding, collagenase-inhibiting, and gadolinium-modified peptide amphiphile micelles (MCG PAMs) are developed. Monocyte chemoattractant protein-1 (MCP-1) binds to C-C chemokine receptor-2 expressed on pathological cell types present within plaques. Through the peptide binding motif of MCP-1, MCG PAMs bind to monocytes and vascular smooth muscle cells in vitro. Moreover, using magnetic resonance imaging, MCG PAMs show enhanced targeting and successful detection of plaques in diseased mice in vivo and act as contrast agents for molecular imaging. Through the collagenase-cleaving peptide sequence of collagen [VPMS-MRGG], MCG PAMs can compete for collagenases that degrade the fibrous cap of plaques, providing therapy. MCG PAM-treated mice show increased fibrous cap thickness by 61% and 113% histologically compared to nontargeting micelle- or PBS-treated mice (p = 0.0075 and 0.001, respectively). Overall, this novel multimodal nanoparticle offers new theranostic opportunities for noninvasive diagnosis and treatment of atherosclerotic plaques.

Fibronectin-targeted dual-acting micelles for combination therapy of metastatic breast cancer

Stage IV breast cancer, which has a high risk of invasion, often develops into metastases in distant organs, especially in the lung, and this could threaten the lives of women. Thus, the development of more advanced therapeutics that can efficiently target metastatic foci is crucial. In this study, we built an dual-acting therapeutic strategy using micelles with high stability functionalized with fibronectin-targeting CREKA peptides encapsulating two slightly soluble chemotherapy agents in water, doxorubicin (D) and vinorelbine (V), which we termed C-DVM. We found that small C-DVM micelles could efficiently codeliver drugs into 4T1 cells and disrupt microtubule structures. C-DVM also exhibited a powerful ability to eradicate and inhibit invasion of 4T1 cells. Moreover, an in vivo pharmacokinetics study showed that C-DVM increased the drug circulation half-life and led to increased enrichment of drugs in lung metastatic foci after 24 h. Moreover, dual-acting C-DVM treatment led to 90% inhibition of metastatic foci development and reduced invasion of metastases. C-DVM could potentially be used as a targeted treatment for metastasis and represents a new approach with higher therapeutic efficacy than conventional chemotherapy for stage IV breast cancer that could be used in the future.

Targeting hemostasis-related moieties for tumor treatment

Under normal conditions, the hemostatic system, that includes the involvement of the coagulation response and platelets, is anatomically and functionally inseparable from the vasculature. However, the hemostatic response always occurs in a wide range of tumors because of the high expression of coagulation initiator tissue factor (TF) in many tumor tissues, and due to the leakage of coagulation factors and platelets from the circulation system into the tumor interstitium through abnormal tumor vessels. Therefore, in addition to TF, these coagulation factors, platelets, the central moiety thrombin, the final product fibrin, and fibronectin, which is capable of stabilizing coagulation clots, are also abundant in tumors. These hemostasis-related moieties (HRMs), including TF, thrombin, fibrin, fibronectin, and platelets, are also closely associated with tumor progression, e.g., primary tumor growth and distal metastasis. The hemostatic response only occurs under pathological conditions, such as tumors, thrombosis, and atherosclerosis other than in normal tissues. The HRMs within tumors are also highly specific, establishing functional and therapeutic targets for tumor treatment. Therefore, strategies including active targeting to these moieties, modulation of HRMs deposited in the tumor microenvironment to improve tumor drug delivery, activation of prodrug by the coagulation complex formed during coagulation response, and direct inhibition of the tumor-promoting activity of HRMs could be designed for tumor therapy. In this review, we summarize various strategies that target HRMs for tumor treatment.

A Bioinspired Nanoprobe with Multilevel Responsive T1 -Weighted MR Signal-Amplification Illuminates Ultrasmall Metastases

Metastasis remains the major cause of death in cancer patients. Thus, there is a need to sensitively detect tumor metastasis, especially ultrasmall metastasis, for early diagnosis and precise treatment of cancer. Herein, an ultrasensitive T₁ -weighted magnetic resonance imaging (MRI) contrast agent, UMFNP-CREKA is reported. By conjugating the ultrasmall manganese ferrite nanoparticles (UMFNPs) with a tumor-targeting penta-peptide CREKA (Cys-Arg-Glu-Lys-Ala), ultrasmall breast cancer metastases are accurately detected. With a behavior similar to neutrophils' immunosurveillance process for eliminating foreign pathogens, UMFNP-CREKA exhibits a chemotactic "targeting-activation" capacity. UMFNP-CREKA is recruited to the margin of tumor metastases by the binding of CREKA with fibrin-fibronectin complexes, which are abundant around tumors, and then release of manganese ions (Mn²⁺ ) to the metastasis in response to pathological parameters (mild acidity and elevated H₂ O₂ ). The localized release of Mn²⁺ and its interaction with proteins affects a marked amplification of T₁ -weighted magnetic resonance (MR) signals. In vivo T₁ -weighted MRI experiments reveal that UMFNP-CREKA can detect metastases at an unprecedented minimum detection limit of 0.39 mm, which has significantly extended the detection limit of previously reported MRI probe.

Large-scale generation of functional mRNA-encapsulating exosomes via cellular nanoporation

Exosomes are attractive as nucleic-acid carriers because of their favourable pharmacokinetic and immunological properties and their ability to penetrate physiological barriers that are impermeable to synthetic drug-delivery vehicles. However, inserting exogenous nucleic acids, especially large messenger RNAs, into cell-secreted exosomes leads to low yields. Here we report a cellular-nanoporation method for the production of large quantities of exosomes containing therapeutic mRNAs and targeting peptides. We transfected various source cells with plasmid DNAs and stimulated the cells with a focal and transient electrical stimulus that promotes the release of exosomes carrying transcribed mRNAs and targeting peptides. Compared with bulk electroporation and other exosome-production strategies, cellular nanoporation produced up to 50-fold more exosomes and a more than 10³-fold increase in exosomal mRNA transcripts, even from cells with low basal levels of exosome secretion. In orthotopic phosphatase and tensin homologue (PTEN)-deficient glioma mouse models, mRNA-containing exosomes restored tumour-suppressor function, enhanced inhibition of tumour growth and increased survival. Cellular nanoporation may enable the use of exosomes as a universal nucleic-acid carrier for applications requiring transcriptional manipulation.

Interface-Enrichment-Induced Instability and Drug-Loading-Enhanced Stability in Inhalable Delivery of Supramolecular Filaments

Filamentous microorganisms traveling in aerosol particles display enhanced deposition and retention in the lungs. Inspired by this shape-related biological effect, we report here on the use of supramolecular filaments as potential inhalable drug carriers within aerosols via jet nebulization. We found that the peptide design and supramolecular stability play a crucial role in the interfacial stability and aerosolization properties of the supramolecular filaments. Monomeric units with a positively charged C-terminus produced filaments with reduced aerosol stability, promoting morphological changes after nebulization. Conversely, having a neutral or negatively charged terminus yielded filaments with enhanced stability, where supramolecular integrity is maintained with only reduced length. Our results suggest that molecular enrichment at the air-liquid interface during nebulization is the primary factor to deplete the monomeric peptide amphiphiles in solution, accounting for the observed morphological disruption/transitions. Importantly, encapsulation of drugs and dyes within filaments notably stabilize their supramolecular structure during nebulization, and the loaded filaments exhibit a linear release profile from a nebulizer device. We envision the use of this supramolecular carrier system as an effective platform for the inhalation-based treatment of many lung diseases.

Hydroxyapatite-binding micelles for the detection of vascular calcification in atherosclerosis

Atherosclerosis is a chronic disease characterized by the formation of calcified, arterial plaques. Microcalcifications (5 μm to 100 μm), mainly composed of hydroxyapatite (HA, Ca5(PO4)3(OH)), develop in the fibrous caps of atherosclerotic plaques and can trigger plaque rupture due to the loss of compliance and elasticity. Ultimately, plaque rupture can cause arterial occlusion and embolization and result in ischemic events such as strokes and myocardial infarctions. Unfortunately, current imaging technologies used to detect calcifications are limited by low signal-to-noise ratio or use invasive procedures that pose risk of arterial dissection. To mitigate these drawbacks, in our study, we developed a novel, fluorescently-labeled peptide amphiphile micelle (PAM) that uses a 12 amino acid HA-binding peptide (HABP) [SVSVGMKPSPRP] to target and detect atherosclerotic calcification (HA PAM). Our results show HA PAMs can successfully target HA microcrystals with a strong binding affinity (KD = 6.26 ± 1.2 μM) in vitro. In addition, HA PAMs detected HA mineralization (HA PAM vs. non-targeting micelle, p≤ 0.001; HA PAM vs. scrambled HABP PAM, p≤ 0.01) formed by calcifying mouse aortic vascular smooth muscle cells (MOVAS). Moreover, HA PAMs successfully detected calcifications in atherosclerotic mouse models as well as in patient-derived arteries. Our studies show that HA PAMs show promise as calcium-targeting nanoparticles for the detection of calcifications in atherosclerosis.

Ultrasmall Core-Shell Silica Nanoparticles for Precision Drug Delivery in a High-Grade Malignant Brain Tumor Model

PURPOSE

Small-molecule inhibitors have revolutionized treatment of certain genomically defined solid cancers. Despite breakthroughs in treating systemic disease, central nervous system (CNS) metastatic progression is common, and advancements in treating CNS malignancies remain sparse. By improving drug penetration across a variably permeable blood-brain barrier and diffusion across intratumoral compartments, more uniform delivery and distribution can be achieved to enhance efficacy.

EXPERIMENTAL DESIGN

Ultrasmall fluorescent core-shell silica nanoparticles, Cornell prime dots (C' dots), were functionalized with α_v integrin-binding (cRGD), or nontargeting (cRAD) peptides, and PET labels (¹²⁴I, ⁸⁹Zr) to investigate the utility of dual-modality cRGD-C' dots for enhancing accumulation, distribution, and retention (ADR) in a genetically engineered mouse model of glioblastoma (mGBM). mGBMs were systemically treated with ¹²⁴I-cRGD- or ¹²⁴I-cRAD-C' dots and sacrificed at 3 and 96 hours, with concurrent intravital injections of FITC-dextran for mapping blood-brain barrier breakdown and the nuclear stain Hoechst. We further assessed target inhibition and ADR following attachment of dasatinib, creating nanoparticle-drug conjugates (Das-NDCs). Imaging findings were confirmed with ex vivo autoradiography, fluorescence microscopy, and p-S6RP IHC.

RESULTS

Improvements in brain tumor delivery and penetration, as well as enhancement in the ADR, were observed following administration of integrin-targeted C' dots, as compared with a nontargeted control. Furthermore, attachment of the small-molecule inhibitor, dasatinib, led to its successful drug delivery throughout mGBM, demonstrated by downstream pathway inhibition.

CONCLUSIONS

These results demonstrate that highly engineered C' dots are promising drug delivery vehicles capable of navigating the complex physiologic barriers observed in a clinically relevant brain tumor model.

Synthesis and Preclinical Evaluation of the Fibrin-Binding Cyclic Peptide 18F-iCREKA: Comparison with Its Contrasted Linear Peptide

Purpose

Cys-Arg-Glu-Lys-Ala (CREKA) is a pentapeptide which can target fibrin-fibronectin complexes. Our previous study has built a probe called iCREKA which was based on CREKA and has proved the feasibility and specificity of iCREKA by the fluorescence experiment. The purpose of this study is to achieve the ¹⁸F-labeled iCREKA and make preclinical evaluation of the ¹⁸F-iCREKA with comparison of its contrasted linear peptide (LP).

Methods

CREKA, LP, and iCREKA were labeled by the Al¹⁸F labeling method, respectively. These ¹⁸F-labeled peptides were evaluated by the radiochemistry, binding affinity, in vitro stability, in vivo stability, micro-PET imaging, and biodistribution tests.

Results

¹⁸F-NOTA-iCREKA was stable both in vitro and in vivo. However, ¹⁸F-NOTA-CREKA and ¹⁸F-NOTA-LP were both unstable. The FITC or ¹⁸F-labeled iCREKA could be abundantly discovered only in matrix metalloproteinases- (MMPs-) 2/9 highly expressed U87MG cells, while the FITC or ¹⁸F-labeled LP could also be abundantly discovered in MMP-2/9 lowly expressed Caov3 cells. Biodistribution and micropositron emission tomography (PET) imaging revealed that the U87MG xenografts showed a higher uptake of ¹⁸F-NOTA-iCREKA than ¹⁸F-NOTA-LP while the Caov3 xenografts showed very low uptake of both ¹⁸F-NOTA-iCREKA and ¹⁸F-NOTA-LP. The tumor-to-muscle (T/M) ratio of ¹⁸F-NOTA-iCREKA (9.93 ± 0.42) was obviously higher than ¹⁸F-NOTA-LP (2.69 ± 0.35) in U87MG xenografts.

Conclusions

The novel CREKA-based probe ¹⁸F-NOTA-iCREKA could get a high uptake in U87MG cells and high T/M ratio in U87MG mice. It was more stable and specific than the ¹⁸F-NOTA-LP.

Concepts of nanoparticle cellular uptake, intracellular trafficking, and kinetics in nanomedicine

Nanoparticle-based therapeutics and diagnostics are commonly referred to as nanomedicine and may significantly impact the future of healthcare. However, the clinical translation of these technologies is challenging. One of these challenges is the efficient delivery of nanoparticles to specific cell populations and subcellular targets in the body to elicit desired biological and therapeutic responses. It is critical for researchers to understand the fundamental concepts of how nanoparticles interact with biological systems to predict and control in vivo nanoparticle transport for improved clinical benefit. In this overview article, we review and discuss cellular internalization pathways, summarize the field`s understanding of how nanoparticle physicochemical properties affect cellular interactions, and explore and discuss intracellular nanoparticle trafficking and kinetics. Our overview may provide a valuable resource for researchers and may inspire new studies to expand our current understanding of nanotechnology-biology interactions at cellular and subcellular levels with the goal to improve clinical translation of nanomedicines.

Nanoparticle-based diagnostic and therapeutic systems for brain tumors

Many theranostic nanoparticles have been tailored for high-efficiency diagnostic or therapeutic agents or applied as carriers and might provide new possibilities for brain tumor diagnosis and treatment.