Peptide-based targeting strategies for simultaneous imaging and therapy with nanovectors

Peptide-conjugated Nanoparticle Platforms for Targeted Delivery, Imaging, and Biosensing Applications

Peptides have become an indispensable tool in engineering of multifunctional nanostructure platforms for biomedical applications such as targeted drug and gene delivery, imaging and biosensing. They can be covalently incorporated into a variety of nanoparticles (NPs) including polymers, metallic nanoparticles, and others. Using different bioconjugation techniques, multifunctional peptide-modified NPs can be formulated to produce therapeutical and diagnostic platforms offering high specificity, lower toxicity, biocompatibility, and stimuli responsive behavior. Targeting peptides can direct the nanoparticles into specific tissues for targeted drug and gene delivery and imaging applications due to their specificity towards certain receptors. Furthermore, due to their stimuli-responsive features, they can offer controlled release of therapeutics into desired sites of disease. In addition, peptide-based biosensors and imaging agents can provide non-invasive detection and monitoring of diseases including cancer, infectious diseases, and neurological disorders. In this review, we covered the design and formulation of recent peptide-based NP platforms, as well as their utilization in in vitro and in vivo applications such as targeted drug and gene delivery, targeting, sensing, and imaging applications. In the end, we provided the future outlook to design new peptide conjugated nanomaterials for biomedical applications.

Targeting androgen receptor (AR) with a synthetic peptide increases apoptosis in triple negative breast cancer and AR-expressing prostate cancer cell lines

BACKGROUND

The androgen receptor (AR) has been studied as an approach to cancer therapy.

AIMS

We used human breast cancer-derived cells with high, low, and very low expression levels of AR, in addition to prostate cancer-derived LNCaP and DU-145 cells as a positive and negative controls to examine apoptosis caused by a synthetic peptide that targets ARs.

METHODS AND RESULTS

The peptide was produced to inhibit AR transactivation in breast cancer cell lines. We then measured cell viability, caspase-3 activity, and the ratio of Bax/Bcl-2. The findings indicated that the peptide (100-500 nM) in the presence of dihydrotestosterone (DHT) reduced cell growth in cells with high and low expression level of AR (p < .001), but not in cells with very low levels of AR. Treatment with 100-500 nM of peptide activated caspase-3 and increased the ratio of Bax/Bcl-2 in cells with high and low expression levels of AR. Also, increasing concentrations of the peptide (100-500 nM) reduced BrdU incorporation in the presence of DHT and promoted apoptosis in cells with high and low expression levels of AR (p < .001).

CONCLUSION

The findings indicate the peptide significantly increased apoptosis in cancer cells.

Functional Diversity in Radiolabeled Nanoceramics and Related Biomaterials for the Multimodal Imaging of Tumors

Nanotechnology advances have the potential to assist toward the earlier detection of diseases, giving increased accuracy for diagnosis and helping to personalize treatments, especially in the case of noncommunicative diseases (NCDs) such as cancer. The main advantage of nanoparticles, the scaffolds underpinning nanomedicine, is their potential to present multifunctionality: synthetic nanoplatforms for nanomedicines can be tailored to support a range of biomedical imaging modalities of relevance for clinical practice, such as, for example, optical imaging, computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). A single nanoparticle has the potential to incorporate myriads of contrast agent units or imaging tracers, encapsulate, and/or be conjugated to different combinations of imaging tags, thus providing the means for multimodality diagnostic methods. These arrangements have been shown to provide significant improvements to the signal-to-noise ratios that may be obtained by molecular imaging techniques, for example, in PET diagnostic imaging with nanomaterials versus the cases when molecular species are involved as radiotracers. We surveyed some of the main discoveries in the simultaneous incorporation of nanoparticulate materials and imaging agents within highly kinetically stable radio-nanomaterials as potential tracers with (pre)clinical potential. Diversity in function and new developments toward synthesis, radiolabeling, and microscopy investigations are explored, and preclinical applications in molecular imaging are highlighted. The emphasis is on the biocompatible materials at the forefront of the main preclinical developments, e.g., nanoceramics and liposome-based constructs, which have driven the evolution of diagnostic radio-nanomedicines over the past decade.

Perspectives and trends in advanced optical and electrochemical biosensors based on engineered peptides

With the advancement of life medicine, in vitro diagnostics (IVD) technology has become an auxiliary tool for early diagnosis of diseases. However, biosensors for IVD now face some disadvantages such as poor targeting, significant antifouling properties, low density of recognized molecules, and poor stability. In recent years, peptides have been demonstrated to have various functions in unnatural biological systems, such as targeting properties, antifouling properties, and self-assembly properties, which indicates that peptides can be engineered. These properties of peptides, combined with their good biocompatibility, can be well applied to the design of biosensors to solve the problems mentioned above. This review provides an overview of the properties of engineered functional peptides and their applications in enhancing biosensor performance, mainly in the field of optics and electrochemistry.

Diagnostic and Therapeutic Approaches for Glioblastoma and Neuroblastoma Cancers Using Chlorotoxin Nanoparticles

Glioblastoma multiforme (GB) and high-risk neuroblastoma (NB) are known to have poor therapeutic outcomes. As for most cancers, chemotherapy and radiotherapy are the current mainstay treatments for GB and NB. However, the known limitations of systemic toxicity, drug resistance, poor targeted delivery, and inability to access the blood-brain barrier (BBB), make these treatments less satisfactory. Other treatment options have been investigated in many studies in the literature, especially nutraceutical and naturopathic products, most of which have also been reported to be poorly effective against these cancer types. This necessitates the development of treatment strategies with the potential to cross the BBB and specifically target cancer cells. Compounds that target the endopeptidase, matrix metalloproteinase 2 (MMP-2), have been reported to offer therapeutic insights for GB and NB since MMP-2 is known to be over-expressed in these cancers and plays significant roles in such physiological processes as angiogenesis, metastasis, and cellular invasion. Chlorotoxin (CTX) is a promising 36-amino acid peptide isolated from the venom of the deathstalker scorpion, Leiurus quinquestriatus, demonstrating high selectivity and binding affinity to a broad-spectrum of cancers, especially GB and NB through specific molecular targets, including MMP-2. The favorable characteristics of nanoparticles (NPs) such as their small sizes, large surface area for active targeting, BBB permeability, etc. make CTX-functionalized NPs (CTX-NPs) promising diagnostic and therapeutic applications for addressing the many challenges associated with these cancers. CTX-NPs may function by improving diffusion through the BBB, enabling increased localization of chemotherapeutic and genotherapeutic drugs to diseased cells specifically, enhancing imaging modalities such as magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), optical imaging techniques, image-guided surgery, as well as improving the sensitization of radio-resistant cells to radiotherapy treatment. This review discusses the characteristics of GB and NB cancers, related treatment challenges as well as the potential of CTX and its functionalized NP formulations as targeting systems for diagnostic, therapeutic, and theranostic purposes. It also provides insights into the potential mechanisms through which CTX crosses the BBB to bind cancer cells and provides suggestions for the development and application of novel CTX-based formulations for the diagnosis and treatment of GB and NB in the future.

Generation of peptides using phage display technology for cancer diagnosis and molecular imaging

Cancer is one of the leading causes of mortality worldwide; nearly 10 million people died from it in 2020. The high mortality rate results from the lack of effective screening approaches where early detection cannot be achieved, reducing the chance of early intervention to prevent cancer development. Non-invasive and deep-tissue imaging is useful in cancer diagnosis, contributing to a visual presentation of anatomy and physiology in a rapid and safe manner. Its sensitivity and specificity can be enhanced with the application of targeting ligands with the conjugation of imaging probes. Phage display is a powerful technology to identify antibody- or peptide-based ligands with effective binding specificity against their target receptor. Tumour-targeting peptides exhibit promising results in molecular imaging, but the application is limited to animals only. Modern nanotechnology facilitates the combination of peptides with various nanoparticles due to their superior characteristics, rendering novel strategies in designing more potent imaging probes for cancer diagnosis and targeting therapy. In the end, a myriad of peptide candidates that aimed for different cancers diagnosis and imaging in various forms of research were reviewed.

Identification of a novel peptide ligand for the cancer-specific receptor mutation EGFRvIII using high-throughput sequencing of phage-selected peptides

We report here the selection and characterization of a novel peptide ligand using phage display targeted against the cancer-specific epidermal growth factor tyrosine kinase receptor mutation variant III (EGFRvIII). This receptor is expressed in several kinds of cancer: ovarian cancer, breast cancer and glioblastoma, but not in normal tissues. A 12-mer random peptide library was screened against EGFRvIII. Phage-selected peptides were sequenced in high-throughput by next generation sequencing (NGS), and their diversity was studied to identify highly abundant clones expected to bind with the highest affinities to EGFRvIII. The enriched peptides were characterized and their binding capacity towards stable cell lines expressing EGFRvIII, EGFR wild type (EGFR WT), or a low endogenous level of EGFR WT was confirmed by flow cytometry analysis. The best peptide candidate, VLGREEWSTSYW, was synthesized, and its binding specificity towards EGFRvIII was validated in vitro. Additionally, computational docking analysis suggested that the identified peptide binds selectively to EGFRvIII. The novel VLGREEWSTSYW peptide is thus a promising EGFRvIII-targeting agent for future applications in cancer diagnosis and therapy.

Nontoxic Tumor-Targeting Optical Agents for Intraoperative Breast Tumor Imaging

Precise identification of the tumor margins during breast-conserving surgery (BCS) remains a challenge given the lack of visual discrepancy between malignant and surrounding normal tissues. Therefore, we developed a fluorescent imaging agent, ICG-p28, for intraoperative imaging guidance to better aid surgeons in achieving negative margins in BCS. Here, we determined the pharmacokinetics (PK), biodistribution, and preclinical toxicity of ICG-p28. The PK and biodistribution of ICG-p28 indicated rapid tissue uptake and localization at tumor lesions. There were no dose-related effect and no significant toxicity in any of the breast cancer and normal cell lines tested. Furthermore, ICG-p28 was evaluated in clinically relevant settings with transgenic mice that spontaneously developed invasive mammary tumors. Intraoperative imaging with ICG-p28 showed a significant reduction in the tumor recurrence rate. This simple, nontoxic, and cost-effective method can offer a new approach that enables surgeons to intraoperatively identify tumor margins and potentially improves overall outcomes by reducing recurrence rates.

Anti-cancer peptide-based therapeutic strategies in solid tumors

Background

Nowadays, conventional medical treatments such as surgery, radiotherapy, and chemotherapy cannot cure all types of cancer. A promising approach to treat solid tumors is the use of tumor-targeting peptides to deliver drugs or active agents selectively.

Result

Introducing beneficial therapeutic approaches, such as therapeutic peptides and their varied methods of action against tumor cells, can aid researchers in the discovery of novel peptides for cancer treatment. The biomedical applications of therapeutic peptides are highly interesting. These peptides, owing to their high selectivity, specificity, small dimensions, high biocompatibility, and easy modification, provide good opportunities for targeted drug delivery. In recent years, peptides have shown considerable promise as therapeutics or targeting ligands in cancer research and nanotechnology.

Conclusion

 This study reviews a variety of therapeutic peptides and targeting ligands in cancer therapy. Initially, three types of tumor-homing and cell-penetrating peptides (CPPs) are described, and then their applications in breast, glioma, colorectal, and melanoma cancer research are discussed.

Investigating the role of peptides in effective therapies against cancer

Early diagnosis and effective treatment of cancer are challenging. To diagnose and treat cancer effectively and to overcome these challenges, fundamental innovations in traditional diagnosis and therapy are necessary. Peptides can be very helpful in this regard due to their potential and diversity. To enhance the therapeutic potential of peptides, their limitations must be properly identified and their structures engineered and modified for higher efficiency. Promoting the bioavailability and stability of peptides is one of the main concerns. Peptides can also be effective in different areas of targeting, alone or with the help of other therapeutic agents. There has been a lot of research in this area, and the potential for variability of peptides will continue to improve this process. Another promising area in which peptides can help treat cancer is peptide vaccines, which are undergoing promising research, and high throughput technologies can lead to fundamental changes in this area. Peptides have been effective in almost all areas of cancer treatment, and some have even gone through clinical phases. However, many barriers need to be overcome to reach the desired point. The purpose of this review is to evaluate the mechanisms associated with peptides in the diagnosis and treatment of cancer. Therefore, related studies in this area will be discussed.

Preparation and In Vitro Evaluation of RITUXfab-Decorated Lipoplexes to Improve Delivery of siRNA Targeting C1858T PTPN22 Variant in B Lymphocytes

Autoimmune endocrine disorders, such as type 1 diabetes (T1D) and thyroiditis, at present are treated with only hormone replacement therapy. This emphasizes the need to identify personalized effective immunotherapeutic strategies targeting T and B lymphocytes. Among the genetic variants associated with several autoimmune disorders, the C1858T polymorphism of the protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene, encoding for Lyp variant R620W, affects the innate and adaptive immunity. We previously exploited a novel personalized immunotherapeutic approach based on siRNA delivered by liposomes (lipoplexes) that selectively inhibit variant allele expression. In this manuscript, we improved lipoplexes carrying siRNA for variant C1858T by functionalizing them with Fab of Rituximab antibody (Ritux_Fab-Lipoplex) to specifically target B lymphocytes in autoimmune conditions, such as T1D. Ritux_Fab-Lipoplexes specifically bind to B lymphocytes of the human Raji cell line and of human PBMC of healthy donors. Ritux_Fab-Lipoplexes have impact on the function of B lymphocytes of T1D patients upon CpG stimulation showing a higher inhibitory effect on total cell proliferation and IgM+ plasma cell differentiation than the not functionalized ones. These results might open new pathways of applicability of Ritux_Fab-Lipoplexes, such as personalized immunotherapy, to other autoimmune disorders, where B lymphocytes are the prevalent pathogenic immunocytes.

Nanoparticles modified with vasculature-homing peptides for targeted cancer therapy and angiogenesis imaging

The two major challenges in cancer treatment include lack of early detection and ineffective therapies with various side effects. Angiogenesis is the key process in the growth, survival, invasiveness, and metastasis of many of cancerous tumors. Imaging of the angiogenesis could lead to diagnosis of tumors in the early stage and evaluation of the therapeutic responses. Angiogenic blood vessels express specific molecular markers different from normal blood vessels (in level or kind). This fact would make the tumor vasculature a suitable site to target therapeutics and imaging agents within the tumor. Surface modified nanoparticles using peptide ligands with high binding affinity to the vasculature markers, provide efficient delivery of therapeutic and imaging agents, while avoiding undesirable side effects. In this review, we discuss discoveries of various tumor targeting peptides useful for tumor angiogenesis imaging and targeted therapy with emphasis on surface modified nanomedicines using vasculature targeting peptides.

Cell surface nucleolin as active bait for nanomedicine in cancer therapy: a promising option

Conventional chemotherapy used against cancer is mostly limited due to their non-targeted nature, affecting normal tissue and causing undesirable toxic effects to the affected tissue. With the aim of improving these treatments both therapeutically and in terms of their safety, numerous studies are currently being carried out using nanoparticles (NPs) as a vector combining tumor targeting and carrying therapeutic tools. In this context, it appears that nucleolin, a molecule over-expressed on the surface of tumor cells, is an interesting therapeutic target. Several ligands, antagonists of nucleolin of various origins, such as AS1411, the F3 peptide and the multivalent pseudopeptide N6L have been developed and studied as therapeutic tools against cancer. Over the last ten years or so, numerous studies have been published demonstrating that these antagonists can be used as tumor targeting agents with NPs from various origins. Focusing on nucleolin ligands, the aim of this article is to review the literature recently published or under experimentation in our research team to evaluate the efficacy and future development of these tools as anti-tumor agents.

Characteristics and therapeutic applications of antimicrobial peptides

The demand for novel antimicrobial compounds is rapidly growing due to the phenomenon of antibiotic resistance in bacteria. In response, numerous alternative approaches are being taken including use of polymers, metals, combinatorial approaches, and antimicrobial peptides (AMPs). AMPs are a naturally occurring part of the immune system of all higher organisms and display remarkable broad-spectrum activity and high selectivity for bacterial cells over host cells. However, despite good activity and safety profiles, AMPs have struggled to find success in the clinic. In this review, we outline the fundamental properties of AMPs that make them effective antimicrobials and extend this into three main approaches being used to help AMPs become viable clinical options. These three approaches are the incorporation of non-natural amino acids into the AMP sequence to impart better pharmacological properties, the incorporation of AMPs in hydrogels, and the chemical modification of surfaces with AMPs for device applications. These approaches are being developed to enhance the biocompatibility, stability, and/or bioavailability of AMPs as clinical options.

Targeting and therapeutic peptide-based strategies for polycystic kidney disease

Polycystic kidney disease (PKD) is characterized by progressive cyst growth and is a leading cause of renal failure worldwide. Currently, there are limited therapeutic options available to PKD patients, and only one drug, tolvaptan, has been FDA-approved to slow cyst progression. Similar to other small molecule drugs, however, tolvaptan is costly, only moderately effective, and causes adverse events leading to high patient dropout rates. Peptides may mitigate many drawbacks of small molecule drugs, as they can be highly tissue-specific, biocompatible, and economically scaled-up. Peptides can function as targeting ligands that direct therapies to diseased renal tissue, or be potent as therapeutic agents themselves. This review discusses various aberrant signaling pathways in PKD and renal receptors that can be potential targets of peptide-mediated strategies. Additionally, peptides utilized in other kidney applications, but may prove useful in the context of PKD, are highlighted. Insights into novel peptide-based solutions that have potential to improve clinical management of PKD are provided.

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.

Systematic overview of soft materials as a novel frontier for MRI contrast agents

Magnetic resonance imaging (MRI) is a well-known diagnostic technique used to obtain high quality images in a non-invasive manner. In order to increase the contrast between normal and pathological regions in the human body, positive (T1) or negative (T2) contrast agents (CAs) are commonly intravenously administered. The most efficient class of T1-CAs are based on kinetically stable and thermodynamically inert gadolinium complexes. In the last two decades many novel macro- and supramolecular CAs have been proposed. These approaches have been optimized to increase the performance of the CAs in terms of the relaxivity values and to reduce the administered dose, decreasing the toxicity and giving better safety and pharmacokinetic profiles. The improved performances may also allow further information to be gained on the pathological and physiological state of the human body. The goal of this review is to report a systematic overview of the nanostructurated CAs obtained and developed by manipulating soft materials at the nanometer scale. Specifically, our attention is centered on recent examples of fibers, hydrogels and nanogel formulations, that seem particularly promising for overcoming the problematic issues that have recently pushed the European Medicines Agency (EMA) to withdraw linear CAs from the market.

Gd(iii)-nanostructurated Constrast Agents (CAs) for Magnetic Resonance Imaging (MRI) can be designed and developed by manipulating soft material, including fibers, hydrogels and nanogels, in the nanometer scale.

Targeting strategies for superparamagnetic iron oxide nanoparticles in cancer therapy

Among various nanoparticles, superparamagnetic iron oxide nanoparticles (SPIONs) have been increasingly studied for their excellent superparamagnetism, magnetic heating properties, and enhanced magnetic resonance imaging (MRI). The conjugation of SPIONs with drugs to obtain delivery nanosystems has several advantages including magnetic targeted functionalization, in vivo imaging, magnetic thermotherapy, and combined delivery of anticancer agents. To further increase the targeting efficiency of drugs through a delivery nanosystem based on SPIONs, additional targeting moieties including transferrin, antibodies, aptamers, hyaluronic acid, folate, and targeting peptides are coated onto the surface of SPIONs. Therefore, this review summarizes the latest progresses in the conjugation of targeting molecules and drug delivery nanosystems based on SPIONs, especially focusing on their performances to develop efficient targeted drug delivery systems for tumor therapy. STATEMENT OF SIGNIFICANCE: Some magnetic nanoparticle-based nanocarriers loaded with drugs were evaluated in patients and did not produce convincing results, leading to termination of clinical development in phase II/III. An alternative strategy for drug delivery systems based on SPIONs is the conjugation of these systems with targeting segments such as transferrin, antibodies, aptamers, hyaluronic acid, folate, and targeting peptides. These targeting moieties can be recognized by specific integrin/receptors that are overexpressed specifically on the tumor cell surface, resulting in minimizing dosage and reducing off-target effects. This review focuses on magnetic nanoparticle-based nonviral drug delivery systems with targeting moieties to deliver anticancer drugs, with an aim to provide suggestions on the development of SPIONs through discussion.

Surface engineering of nanomaterials with phospholipid-polyethylene glycol-derived functional conjugates for molecular imaging and targeted therapy

In recent years, phospholipid-polyethylene glycol-derived functional conjugates have been widely employed to decorate different nanomaterials, due to their excellent biocompatibility, long blood circulation characteristics, and specific targeting capability. Numerous in vivo studies have demonstrated that nanomedicines peripherally engineered with phospholipid-polyethylene glycol-derived functional conjugates show significantly increased selective and efficient internalization by target cells/tissues. Targeting moieties including small-molecule ligands, peptides, proteins, and antibodies are generally conjugated onto PEGylated phospholipids to decorate liposomes, micelles, hybrid nanoparticles, nanocomplexes, and nanoemulsions for targeted delivery of diagnostic and therapeutic agents to diseased sites. In this review, the synthesis methods of phospholipid-polyethylene glycol-derived functional conjugates, biophysicochemical properties of nanomedicines decorated with these conjugates, factors dominating their targeting efficiency, as well as their applications for in vivo molecular imaging and targeted therapy were summarized and discussed.

Heuristics for the Optimal Presentation of Bioactive Peptides on Polypeptide Micelles

Bioactive peptides describe a very large group of compounds with diverse functions and wide applications, and their multivalent display by nanoparticles can maximize their activities. However, the lack of a universal nanoparticle platform and design rules for their optimal presentation limits the development and application of peptide ligand-decorated nanoparticles. To address this need, we developed a multivalent nanoparticle platform to study the impact of nanoparticle surface hydrophilicity and charge on peptide targeting and internalization by tumor cells. This system consists of micelles of a recombinant elastin-like polypeptide diblock copolymer (ELP_BC) that present genetically encoded peptides at the micelle surface without perturbing the size, shape, stability, or peptide valency of the micelle, regardless of the peptide type. We created the largest extant set of 98 combinations of 15 tumor-homing peptides that are presented on the corona of this ELP_BC micelle via 8 different peptide linkers that vary in their length and charge and also created control micelles that present the linker only. Analysis of the structure-function relationship of tumor cell targeting by this set of peptide-decorated nanoparticles enabled us to derive heuristics to optimize the delivery of peptides based on their physicochemical properties and to identify a peptide that is likely to be a widely useful ligand for targeting across nanoparticle types. This study shows that ELP_BC micelles are a robust and convenient system for the presentation of diverse peptides and provides useful insights into the appropriate presentation of structurally diverse peptide ligands on nanoparticles based on their physicochemical properties.

Self-assembled peptido-nanomicelles as an engineered formulation for synergy-enhanced combinational SDT, PDT and chemotherapy to nasopharyngeal carcinoma

A formulation of self-assembled peptido-nanomicelles has been developed for a combinational treatment of SDT, PDT and chemotherapy to nasopharyngeal carcinoma. In vitro cellular tests and in vivo mice therapy proved effective for targeted tumor growth inhibition. These merits provided a novel approach to non-invasive cancer treatments.

Novel therapeutic interventions in cancer treatment using protein and peptide-based targeted smart systems

Cancer, being the most prevalent and resistant disease afflicting any gender, age or social status, is the ultimate challenge for the scientific community. The new generation therapeutics for cancer management has shifted the approach to personalized/precision medicine, making use of patient- and tumor-specific markers for specifying the targeted therapies for each patient. Peptides targeting these cancer-specific signatures hold enormous potential for cancer therapy and diagnosis. The rapid advancements in the combinatorial peptide libraries served as an impetus to the development of multifunctional peptide-based materials for targeted cancer therapy. The present review outlines benefits and shortcomings of peptides as cancer therapeutics and the potential of peptide modified nanomedicines for targeted delivery of anticancer agents.

Synthetic peptide-labelled micelles for active targeting of cells overexpressing EGF receptors

The goal of nanomedicine is to transport drugs to pathological tissues, reducing side effects while increasing targeting and efficacy. Aggregates grafted by bioactive molecules act as the active targeting agents. Among bioactive molecules, peptides, which are able to recognize overexpressed receptors on cancer cell membranes, appear to be very promising. The aim of this study was to formulate analog peptide-labeled micelles enabled to potentially deliver highly hydrophobic drugs to cancer cells overexpressing epidermal growth factor (EGF) receptor (EGFR). The selected synthetic peptide sequences were anchored to a hydrophobic moiety, aiming to obtain amphiphilic peptide molecules. Mixed micelles were formulated with Pluronic^® F127. These micelles were fully characterized by physico-chemical methods, estimating the critical micellar concentration (CMC) by fluorescence. Their sizes were established by dynamic light scattering (DLS) analysis. Then, micelles were also tested in vitro for their binding capacity to human hepatocellular carcinoma (HCC) cell lines overexpressing EGFR.

Encapsulation of Gold Nanorods with Porphyrins for the Potential Treatment of Cancer and Bacterial Diseases: A Critical Review

Cancer and bacterial diseases have been the most incidental diseases to date. According to the World Health Report 2018, at least every family is affected by cancer around the world. In 2012, 14.1 million people were affected by cancer, and that figure is bound to increase to 21.6 million in 2030. Medicine therefore sorts out ways of treatment using conventional methods which have been proven to have many side effects. Researchers developed photothermal and photodynamic methods to treat both cancer and bacterial diseases. These methods pose fewer effects on the biological systems but still no perfect method has been synthesized. The review serves to explore porphyrin and gold nanorods to be used in the treatment of cancer and bacterial diseases: porphyrins as photosensitizers and gold nanorods as delivery agents. In addition, the review delves into ways of incorporating photothermal and photodynamic therapy aimed at producing a less toxic, more efficacious, and specific compound for the treatment.

Peptide-based building blocks as structural elements for supramolecular Gd-containing MRI contrast agents

Magnetic resonance imaging (MRI) is one of the most important clinic diagnostic tool used to obtain high-quality body images. The administration of low-molecular-weight Gd complex-based MRI contrast agents (CAs) permits to increase the ¹ H relaxation rate of nearby water molecules, thus modulating signal intensity and contrast enhancement. Even if highly accurate, MRI modality suffers from its low sensitivity. Moreover, low-molecular-weight CAs rapidly equilibrate between the intravascular and extravascular spaces after their administration. In order to improve their sensitivity and limit the extravasation phenomenon, several macromolecular and supramolecular multimeric gadolinium complexes (dendrimers, polymers, carbon nanostructures, micelles, and liposomes) have been designed until now. Because of their biocompatibility, low immunogenicity, low cost, and easy synthetic modification, peptides are attractive building blocks for the fabbrication of novel materials for biomedical applications. We report on the state of the art of supramolecular CAs obtained by self-assembly of three different classes of building blocks containing a peptide sequence, a gadolinium complex, and, if necessary, a third functional portion achieving the organization process.

GSH-Activated Light-Up Near-Infrared Fluorescent Probe with High Affinity to αvβ3 Integrin for Precise Early Tumor Identification

The development of tumor-associated, stimuli-driven, turn-on near-infrared (NIR) fluorophores requires urgent attention because of their potential in selective and precise tumor diagnosis. Herein, we describe a NIR fluorescent probe (CyA-cRGD) comprised of a fluorescence reporting unit (a cyanine dye) linked with a GSH-responsive unit (nitroazo aryl ether group) and a tumor-targeting unit (cRGD). The NIR fluorescence of CyA-cRGD with sensitive and selective response to GSH can act as a direct off-on signal reporter for GSH monitoring. Notably, CyA-cRGD possesses improved biocompatibility compared with CyA, which is highly desirable for in vivo fluorescence tracking of cancer. Confocal fluorescence imaging confirmed the tumor-targeting capability and GSH detection ability of CyA-cRGD in tumor cells, normal cells, and coincubated tumor /normal cells and in the three-dimensional multicellular tumor spheroid. Furthermore, it was validated that CyA-cRGD could detect tumor precisely in GSH and integrin α_vβ ₃ high-expressed tumor-bearing mouse models. Importantly, it was confirmed that CyA-cRGD possessed high efficiency for early-stage tumor imaging in mouse models with tumor cells implanted within 72 h. This method provided significant advances toward more in-depth understanding and exploration of tumor imaging, which may potentially be applied for clinical early tumor diagnosis.

From proof-of-concept material to PEGylated and modularly targeted ultrasound-responsive mesoporous silica nanoparticles

In this work we present the synthesis, characterization and in vitro biological evaluation of PEGylated and actively-targeted ultrasound-responsive hybrid mesoporous silica nanoparticles. This work covers the development of the chemical strategies necessary to afford a modular nanocarrier starting from a proof-of-concept material presented in previous work. This functional ultrasound-responsive material can be adapted to different specific pathological conditions by carefully choosing the appropriate targeting moieties. The new ultrasound responsive material is able to target HeLa cells when conjugated with biotin or an RGD peptide. Ultrasound-responsive cytotoxicity towards cancer cells of doxorubicin-loaded nanoparticles is demonstrated in an in vitro cytotoxicity assay.

Targeted delivery of microRNA-199a-3p using self-assembled dipeptide nanoparticles efficiently reduces hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is an aggressive tumor with limited systemic and locoregional modalities of treatment. Although microRNA (miRNA) based therapies have significant potential, their targeted delivery remains a major challenge. miR-199a-3p functions as an important tumor suppressor in HCC, which regulates various cellular processes. Recently, peptide-based nanoparticles (NPs) have been developed to deliver oligonucleotides including miRNA. Here, we describe the synthesis and characterization of arginine α,β-dehydrophenylalanine (RΔF) nanoparticles for the selective delivery of miR-199a-3p to restore dysregulated gene expression in HCC. Targeted delivery was achieved by conjugating lactobionic acid (LA) with RΔF NPs (RΔF-LA NPs), a ligand for the asialoglycoprotein receptor known to be overexpressed in HCC cell lines. RΔF-LA NPs condensed miR-199a-3p had an average size of ∼60nm and a zeta potential of ∼+2.54 mV. RΔF-LA/miR NPs were found to be stable in serum as well as against RNase attack. RΔF-LA/miR NPs showed an enhanced cellular uptake and an efficient delivery of miR-199a-3p leading to a significant increase in miR-199a-3p levels (over 500 fold). The increased miR-199a-3p levels remarkably suppressed cell proliferation and migration as well as induced cellular apoptosis and downregulation of the specific target gene (mTOR) in vitro. RΔF-LA/miR NPs showed high tumor/ low organ ratios after intravenous injection into HCC tumor bearing nude mice. RΔF-LA/miR NPs treated mice demonstrated>50% decline in tumor growth, which also corresponded well with suppression of mTOR protein expression, tumor cell proliferation and increased survival rate (P < 0.05).

CONCLUSION

RΔF-LA/miR NPs showed significantly enhanced delivery of the miRNA which underscores their potential for further development as a therapeutic approach for HCC. (Hepatology 2018;67:1392-1407).

Application of Bld-1-Embedded Elastin-Like Polypeptides in Tumor Targeting

Expression of various molecules on the surface of cancer cells compared to normal cells creates a platform for the generation of various drug vehicles for targeted therapy. Multiple interactions between ligands and their receptors mediated by targeting peptide-modified polymer could enable simultaneous delivery of a drug selectively to target tumor cells, thus limiting side effects resulting from non-specific drug delivery. In this study, we synthesized a novel tumor targeting system by using two key elements: (1) Bld-1 peptide (SNRDARRC), a recently reported bladder tumor targeting peptide identified by using a phage-displayed peptide library, and (2) ELP, a thermally responsive polypeptide. B5V60 containing five Bld-1 peptides and non-targeted ELP77 with a thermal phase-transition over 37 °C were analyzed to determine their bioactivities. Further studies confirmed the superior binding ability of B5V60 to bladder tumor cells and the cellular accumulation of B5V60 in cancer cells was dependent on the expression level of sialyl-Tn antigen (STn), a tumor-associated carbohydrate antigen. Additionally, B5V60 displayed excellent localization in bladder tumor xenograft mice after intravenous injection and was strictly confined to sialyl-Tn antigen-overexpressing tumor tissue. Thus, our newly designed B5V60 showed high potential as a novel carrier for STn-specific targeted cancer therapy or other therapeutic applications.

Robust Anticancer Efficacy of a Biologically Synthesized Tumor Acidity-Responsive and Autophagy-Inducing Functional Beclin 1

As a potent autophagy inducer, Beclin 1 is essential for the initiation of autophagic cell death, and triggering extensive autophagy by targeted delivery of Beclin 1 to tumors has enormous potential to inhibit tumor growth. Yet, the therapeutic application of Beclin 1 is hampered by its inability to internalize into cells and nonselective biodistribution in vivo. To tackle this challenge, we employed a novel Beclin 1 delivery manner by constructing a functional protein (Trx-pHLIP-Beclin 1, TpB) composed of a thioredoxin (Trx) tag, a pH low insertion peptide (pHLIP), and an evolutionarily conserved motif of Beclin 1. This protein could effectively transport Beclin 1 to breast and ovarian cancer cell lines under weakly acidic conditions (pH 6.5), markedly inhibit tumor cell growth and proliferation, and induce obvious autophagy. Furthermore, the in vivo antitumor efficacy of the functional Beclin 1 against an SKOV3 xenograft tumor mouse model was tested via intravenous injection. TpB preferentially accumulated in tumors and exhibited a significantly higher tumor growth inhibition than the nontargeted Beclin 1 control, whereas no overt side effects were observed. Taken together, this study sheds light on the potential application of TpB as a highly efficient yet safe antitumor agent for cancer treatment.

Transfer of Dyes and Drugs into Cells Using EGFR-Targeted Nanosyringes

Selective targeting of drug loaded nanovectors to specific epitopes highly expressed on the surface of cancer cells is a goal for nanotechnologists. We have modified our previously described PEGylated-hydrophilic carbon clusters (PEG-HCCs) so that the epidermal growth factor receptor (EGFR) binding peptide, GE11, is attached using click chemistry at the end of each PEG. The resulting nanosyringe, Pep_EGFR-PEG-HCC, can be loaded with a wide range of hydrophobic drugs and dyes. We show that, both in vitro and in vivo, this payload can be delivered to cancer cells expressing EGFR. We can observe the activation of EGFR and track the normal physiological internalization and recycling/signaling pathways of this tyrosine kinase following binding of Pep_EGFR-PEG-HCC. We also demonstrate the competitive binding of the nanosyringe to EGFR with its normal activator, EGF, as well as observing the colocalization of the nanosyringe with clathrin, the coated pit integral protein. The internalization of the drug/dye loaded nanosyringe can be inhibited by using anti-EGFR antibodies, the drug erlotinib, or Pitstop-1, the clathrin coated pit formation specific inhibitor. To further demonstrate the specificity of the drug loaded nanovectors, we demonstrated that, in both flank and intracranial xenograft mouse models, dye delivery is highly specific to tumors and no other tissues. Finally, using nanosyringes loaded with esterase sensitive fluorescein diacetate, we demonstrated that the drug payloads can be in vivo delivered to the cytosol of cancer cells within the mouse brain.

The Weak Link: Optimization of the Ligand-Nanoparticle Interface To Enhance Cancer Cell Targeting by Polymer Micelles

Many promising targeting ligands are hydrophobic peptides, and these ligands often show limited accessibility to receptors, resulting in suboptimal targeting. A systematic study to elucidate the rules for the design of linkers that optimize their presentation on nanoparticles has not been carried out to date. In this study, we recombinantly synthesized an elastin-like polypeptide diblock copolymer (ELP_BC) that self-assembles into monodisperse micelles. AHNP and EC1, two hydrophobic ErbB2-targeted peptide ligands, were incorporated at the C-terminus of the ELP_BC with an intervening peptide linker. We tested more than 20 designs of peptide linkers, where the linker could be precisely engineered at the gene level to systematically investigate the molecular parameters-sequence, length, and charge-of the peptide linker that optimally assist ligands in targeting the ErbB2 receptor on cancer cells. We found that peptide linkers with a minimal length of 12 hydrophilic amino acids and an overall cationic charge-and that impart a zeta potential of the micelle that is close to neutral-were necessary to enhance the uptake of peptide-modified ELP_BC micelles by cancer cells that overexpress the ErbB2 receptor. This work advances our understanding of the optimal presentation of hydrophobic ligands by nanoparticles and suggests design rules for peptide linkers for targeted delivery by polymer micelles, an emerging class of nanoparticle carriers for drugs and imaging agents.

Multifunctional peptide-lipid nanocomplexes for efficient targeted delivery of DNA and siRNA into breast cancer cells

The development of carriers for the delivery of oligonucleotide therapeutics is essential for the successful translation of gene therapies to the clinic. In the present study, a delivery system, which combines the fusogenic lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) with a well-defined synthetic multifunctional peptide, was produced and optimized for gene delivery, with the aim to develop an efficient gene delivery platform for breast cancer cells. For this purpose, a breast cancer-specific cell targeting peptide (CTP) was incorporated into our leading peptide-based gene delivery system (to generate DEN-K(GALA)-TAT-K(STR)-CTP) to improve its cell-specific internalization, and investigated in combination with a formulation approach (DOPE/1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)). DEN-K(GALA)-TAT-K(STR)-CTP alone efficiently complexed with DNA or siRNA, and promoted efficient cellular uptake, but low levels of gene expression. By adding the formulation approach, synergistic improvements in gene expression and silencing were observed compared to the peptide or formulation approaches alone. Of significance, this current system demonstrated more efficient gene knockdown when compared to the leading commercial siRNA delivery agent Lipofectamine® RNAiMAX. The utility of this system was demonstrated through the delivery of BCL2 (B-cell lymphoma 2) siRNA to MCF-7 cells, which led to near complete knockdown of the Bcl-2 protein, and inhibition of MCF-7 cell migration in a wound healing assay. The present peptide/lipid hybrid system is an excellent candidate for the delivery of DNA or siRNA into breast cancer cells.

STATEMENT OF SIGNIFICANCE

The identification of safe and effective delivery systems for DNA and siRNA is of great importance. Herein, we developed a well-defined, multifunctional and cell-specific lipidic peptide DEN-K(GALA)-TAT-K(STR)-CTP as a breast cancer cell targeted gene delivery vector. When combined with a lipid component (DOTAP/DOPE), the peptide/lipid hybrid system demonstrated higher gene expression or knockdown levels compared to the peptide or lipid approach alone when used to deliver pDNA or siRNA respectively, indicating synergistic enhancement of gene delivery efficiency. Importantly, this delivery strategy achieved greater knockdown of the Bcl-2 protein when compared to the leading commercial siRNA delivery system Lipofectamine® RNAiMAX, suggesting its potential utility for the targeted treatment of Bcl-2 overexpressing breast cancers.

Optical imaging and anticancer chemotherapy through carbon dot created hollow mesoporous silica nanoparticles

Multifunctional nanocarrier-based theranostics is currently considered to solve some key unmet challenges in cancer treatment. Here we report a nanocarrier platform, named carbon dot (CD) created mesoporous hollow organosilica (C-hMOS) nanoparticles, to deliver anticancer drug and to enable optical imaging. The hollow structure was formed by the removal of a nanorod core template, and at the same time, the fluorescent signal was endowed from the heat-treated organosilica network. Thanks to the hollow and mesoporous structure, the C-hMOS effectively loaded doxorubicin (DOX) for cancer chemotherapy. The DOX was released from C-hMOS highly sustainably (over 12days) and pH-dependently (pH 5.0 >pH 7.4). The DOX-loading C-hMOS internalized cancer cells efficiently (>90%), and induced cellular apoptosis including the expression of caspase-3. The treatment of C-hMOS to cancer cells enabled multi-color visualization in vitro, suggesting the possibility of cell tracing. Moreover, when injected intratumorally in mice, the C-hMOS exhibited strong optical signals in vivo along with a high optical stability (over a week). The injected C-hMOS were distributed only a fraction in liver but not in heart, lung, spleen or kidney and displayed good biocompatibility. The DOX-delivering C-hMOS significantly suppressed the in vivo tumor growth associated with apoptotic functions. Taken together, the developed C-hMOS nanoparticles can be a promising nanoplatform for drug delivery and in vivo imaging in cancer treatment.

STATEMENT OF SIGNIFICANCE

Multifunctional nanoparticles that combine chemotherapeutic ability with imaging modality comprise promising platform for cancer theranostics. Here we developed a novel theranostic nanoparticle, i.e., carbon-dot created mesoporous hollow silica nanoparticle, to offer unique merit for this purpose. The in vitro and in vivo findings to support this include: i) carbon dots with 1-2nm size in situ generated discretely and uniformly within silica network, ii) hollow and mesoporous structure effective for loading of DOX at high content, iii) release behavior of DOX in a sustainable and pH-dependent manner, iv) chemotherapeutic efficacy in killing cancer cells and suppressing tumor growth through DOX delivery, and v) carbon dot induced multi-color fluorescence imaging within cells and tumor tissues. These collective multifaceted properties may facilitate the novel carbon dot nanocarriers to be a potential candidate for delivering anticancer drug and non-invasive imaging in cancer treatment.

Biomarkerless targeting and photothermal cancer cell killing by surface-electrically-charged superparamagnetic Fe3O4 composite nanoparticles

A major challenge in cancer therapy is localized targeting of cancer cells for maximum therapeutic effectiveness. However, due to cancer heterogeneities, the biomarkers are either not readily available or specific for effective targeting of cancer cells. The key, therefore, is to develop a new targeting strategy that does not rely on biomarkers. A general hallmark of cancer cells is the much increased level of glycolysis. The loss of highly mobile lactate from the cytoplasm inevitably removes labile inorganic cations to form lactate salts and acids as part of the lactate cycle, creating a net of negative surface charges. This net of negative charges on cancer cell surfaces biophysically distinguishes themselves from normal cells. In this study, cancer cells are targeted by using positively-charged, fluorescent, superparamagnetic Fe₃O₄-composite nanoparticles. The positively-charged Fe₃O₄ composite nanoparticles bind predominantly to cancer cells due to their negatively-charged surfaces. Upon electrical-charge-mediated Fe₃O₄ nanoparticle binding onto cancer cells, irradiation by using an 808 nm laser is subsequently applied to induce photothermal hyperthermia that kills the cancer cells directly. The negatively-charged composite nanoparticles are found, however, not to target and bind the cancer cells due to the electrostatic repulsive force between them. This unique strategy paves a new path for effective targeting and direct cancer cell killing without relying on any biomarkers and anticancer drugs.

CD44v6-Peptide Functionalized Nanoparticles Selectively Bind to Metastatic Cancer Cells

CD44v6 peptide functionalized nanoparticles are fabricated in a facile and controllable way to selectively bind to CD44v6 positive tumor cells with highly efficient anticancer and antimetastatic properties. The reported modular synthesis and facile preparation makes this system highly potent for developing novel multifunctional nanocarriers for therapeutic and/or diagnostic anticancer applications.

Targeting cancer cells via tumor-homing peptide CREKA functional PEG nanoparticles

Targeting cell microenvironment via nano-particle based therapies holds great promise for the treatment of various diseases. One of the main challenges in targeted delivery of nanoparticles for cancer therapy is the reduced localization of delivery vehicles to the tumor site. The therapeutic efficacy of drugs can be improved by recruiting delivery vehicles towards specific region of tumorigenesis in the body. Here, we demonstrate an effective approach in creating PEG particles via water-in-water emulsion technique with a tumor-homing peptide CREKA functionalization. The CREKA conjugated hydrogel nanoparticles were found to be more effective at inducing Doxorubicin (DOX)-mediated apoptosis compared to that of particles conjugated with laminin peptide IKVAV. Fluorescence intensity analysis on confocal micrographs suggested significantly higher cellular uptake of CREKA conjugated PEG particles than internalization of nanoparticles in other groups. We observed that fibrin binding ability of PEG particles could be increased up to 94% through CREKA conjugation. Our results suggest the possibility of cancer cell targeting via CREKA-functional PEG nanoparticles.

Theragnostic ultrasound using microbubbles in the treatment of prostate cancer

The use of gas-filled microbubbles in perfusion monitoring as intravascular ultrasound contrast agents has recently become more common. Additionally, microbubbles are employed as carriers of pharmaceutical substances or genes. Microbubbles have great potential to improve the delivery of therapeutic materials into cells and to modify vascular permeability, causing increased extravasation of drugs and drug carriers. Prostate cancer is the most common neoplasm in Europe and America, with an incidence twice to three times that of lung and colorectal cancer. Its incidence is still rising in Asian countries, including Japan and Korea. In this review, we present current strategies regarding the synthesis of microbubbles with targeted ligands on their surfaces, with a focus on prostate cancer.

A near IR photosensitizer based on self-assembled CdSe quantum dot-aza-BODIPY conjugate coated with poly(ethylene glycol) and folic acid for concurrent fluorescence imaging and photodynamic therapy

Nanocomposite comprised of CdSe quantum dot-thiophene-substituted aza-BODIPY conjugate coated with FA and PEG has been developed for simultaneous fluorescence imaging and photodynamic therapy of HeLa cells via Förster resonance energy transfer.

PAMAM dendrimer based targeted nano-carrier for bio-imaging and therapeutic agents

In the last several decades, researchers have focused on developing suitable drug carriers to deliver pharmaceutical agents to treat cancer diseases.

Vectors for the delivery of radiopharmaceuticals in cancer therapeutics

Internal radiation using radiopharmaceuticals promises efficient cancer therapeutics. The specificity and selectivity required for screening and pinpointing tumor cells for cell-kill has been made possible by targeted ligands based on 'magic bullet' and tracer principle- theories nearing a century. Overexpression of certain receptors has been exploited using biomolecules for targeting. The pragmatic analysis, however, is not as promising compared with the theoretical knowledge of available gamut of vectors and targets. The complex interplay of in vitro and in vivo parameters, and the effect of radionuclides involve a systematic assessment of radiopharmaceuticals as diagnostic and therapeutic agent. This review presents different vectors with their pros and cons, present status and recent design variations followed by a future perspective based on novel approaches.

Multi-stimuli responsive Cu2S nanocrystals as trimodal imaging and synergistic chemo-photothermal therapy agents

A size and shape tuned, multifunctional metal chalcogenide, Cu2S-based nanotheranostic agent is developed for trimodal imaging and multimodal therapeutics against brain cancer cells. This theranostic agent was highly efficient in optical, photoacoustic and X-ray contrast imaging systems. The folate targeted NIR-responsive photothermal ablation in synergism with the chemotherapeutic action of doxorubicin proved to be a rapid precision guided cancer-killing module. The multi-stimuli, i.e., pH-, thermo- and photo-responsive drug release behavior of the nanoconjugates opens up a wider corridor for on-demand triggered drug administration. The simple synthesis protocol, combined with the multitudes of interesting features packed into a single nanoformulation, clearly demonstrates the competing role of this Cu2S nanosystem in future cancer treatment strategies.

Self-assembled autophagy-inducing polymeric nanoparticles for breast cancer interference in-vivo

A peptide-conjugated poly(β-amino ester) that self-assembles into micelle-like nanoparticles is prepared by a convenient and modular supramolecular approach. The polymer-beclin-1 (P-Bec1) nanoparticles display enhanced cytotoxicity to breast cancer cells through induction of autophagy. This approach overcomes two major limitations of the haploinsufficient tumor suppressor Bec1 compared to small-molecule drugs: poor delivery to tumors owing to enzymatic degradation, and unstable, non-specific bio-distribution and targeting in the tumor tissues.

Monoclonal antibody-functionalized multilayered particles: targeting cancer cells in the presence of protein coronas

Engineered particles adsorb biomolecules (e.g., proteins) when introduced in a biological medium to form a layer called a "corona". Coronas, in particular the protein corona, play an important role in determining the surface properties of particles and their targeting abilities. This study examines the influence of protein coronas on the targeting ability of layer-by-layer (LbL)-assembled polymer capsules and core-shell particles functionalized with monoclonal antibodies. Upon exposure of humanized A33 monoclonal antibody (huA33 mAb)-functionalized poly(methacrylic acid) (PMA) capsules or huA33 mAb-PMA particles to human serum, a total of 83 or 65 proteins were identified in the protein coronas, respectively. Human serum of varying concentrations altered the composition of the protein corona. The antibody-driven specific cell membrane binding was qualitatively and quantitatively assessed by flow cytometry and fluorescence microscopy in both the absence and presence of a protein corona. The findings show that although different protein coronas formed in human serum (at different concentrations), the targeting ability of both the huA33 mAb-functionalized PMA capsules and particles toward human colon cancer cells was retained, demonstrating no significant difference compared with capsules and particles in the absence of protein coronas: ∼70% and ∼90% A33-expressing cells were targeted by the huA33 mAb-PMA capsules and particles, respectively, in a mixed cell population. This result demonstrates that the formation of protein coronas did not significantly influence the targeting ability of antibody-functionalized LbL-polymer carriers, indicating that the surface functionality of engineered particles in the presence of protein coronas can be preserved.

Liposomal doxorubicin doubly functionalized with CCK8 and R8 peptide sequences for selective intracellular drug delivery

A new dual-ligand liposomal doxorubicin delivery system, which couples targeting to enhanced cellular uptake and may lead to a more efficient drug delivery system, is here designed and synthetized. Liposomes based on the composition 1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-distearoyl-sn-glycero-3-phosphoethanolamine-Peg2000-R8/(C18)2-L5-SS-CCK8 (87/8/5 mol/mol/mol) were prepared and loaded with doxorubicin. Presence of the two peptides on the external surface is demonstrated by fluorescence resonance energy transfer assay. The combination of the R8 cell-penetrating peptide and of the CCK8 targeting peptide (homing peptide) on the liposome surface is obtained by combining pre-modification and post-modification methods. In the dual-ligand system, the CCK8 peptide is anchored to the liposome surface by using a disulfide bond. This chemical function is inserted in order to promote the selective cleavage of the homing peptide under the reductive conditions expected in proximity of the tumor site, thus allowing targeting and internalization of the liposomal drug.