Self-assembled Peptide Nanoparticles Research Articles

Self-assembled peptide nanoparticles for photodynamic therapy: morphological and mechanical effects on hepatocellular carcinoma cells

Self-assembling peptides, offering favorable biocompatibility, high stability, and easy incorporation of various functionalities, have demonstrated enormous potential for the precise design of next-generation nanodrugs for non-invasive tumor therapy. Peptide-based supramolecular photodynamic therapy (PDT) has shown great promise as an emerging modality for cancer treatment, achieving substantially-enhanced photosensitizer delivery selectivity and treatment efficacy, based on peptide biological activity and self-assembly potential. Although considerable research has been conducted toward fabricating self-assembling peptide-based smart nanodrugs for PDT, few studies have investigated cellular biophysical responses as indicators of tumor function and metabolic state. Here, via atomic force microscopy (AFM)-based morphological and mechanical measurements, including optical microscopy and scanning electron microscopy, we observed, for the first time, variation in membrane stiffness of human liver (HepG2) cancer cells treated with self-assembling peptides serving as a PDT nanodrug. This biophysical information will help to establish a comprehensive understanding of the anticancer effect of peptide-based smart nanodrugs, and highlight the exceptional ability of AFM in determining cell-surface properties.

Molecularly Stimuli-Responsive Self-Assembled Peptide Nanoparticles for Targeted Imaging and Therapy.

Self-assembly has emerged as an extensively used method for constructing biomaterials with sizes ranging from nanometers to micrometers. Peptides have been extensively investigated for self-assembly. They are widely applied owing to their desirable biocompatibility, biodegradability, and tunable architecture. The development of peptide-based nanoparticles often requires complex synthetic processes involving chemical modification and supramolecular self-assembly. Stimuli-responsive peptide nanoparticles, also termed "smart" nanoparticles, capable of conformational and chemical changes in response to stimuli, have emerged as a class of promising materials. These smart nanoparticles find a diverse range of biomedical applications, including drug delivery, diagnostics, and biosensors. Stimuli-responsive systems include external stimuli (such as light, temperature, ultrasound, and magnetic fields) and internal stimuli (such as pH, redox environment, salt concentration, and biomarkers), facilitating the generation of a library of self-assembled biomaterials for biomedical imaging and therapy. Thus, in this review, we mainly focus on peptide-based nanoparticles built by self-assembly strategy and systematically discuss their mechanisms in response to various stimuli. Furthermore, we summarize the diverse range of biomedical applications of peptide-based nanomaterials, including diagnosis and therapy, to demonstrate their potential for medical translation.

Tetrapeptide self-assembled multicolor fluorescent nanoparticles for bioimaging applications

The biocompatibility and biodegradability of peptide self-assembled materials makes them suitable for many biological applications, such as targeted drug delivery, bioimaging, and tracking of therapeutic agents. According to our previous research, self-assembled fluorescent peptide nanoparticles can overcome the intrinsic optical properties of peptides. However, monochromatic fluorescent nanomaterials have many limitations as luminescent agents in biomedical applications. Therefore, combining different fluorescent species into one nanostructure to prepare fluorescent nanoparticles with multiple emission wavelengths has become a very attractive research area in the bioimaging field. In this study, the tetrapeptide Trp-Trp-Trp-Trp (WWWW) was self-assembled into multicolor fluorescent nanoparticles (TPNPs). The results have demonstrated that TPNPs have the blue, green, red and near infrared (NIR) fluorescence emission wavelength. Moreover, TPNPs have shown excellent performance in multicolor bioimaging, biocompatibility, and photostability. The facile preparation and multicolor fluorescence features make TPNPs potentially useful in multiplex bioanalysis and diagnostics.

A structural vaccinology approach for in silico designing of a potential self-assembled nanovaccine against Leishmania infantum

Visceral leishmaniasis (VL) remains a major public health problem across 98 countries. To date, VL has no effective drug. Vaccines, as the most successful breakthroughs in medicine, can promise an effective strategy to fight various diseases. More recently, self-assembled peptide nanoparticles (SAPNs) have attracted considerable attention in the field of vaccine design due to their multivalency. In this study, a SAPN nanovaccine was designed using various immunoinformatics methods. High-ranked epitopes were chosen from a number of antigens, including Leishmania-specific hypothetical protein (LiHy), Leishmania-specific antigenic protein (LSAP), histone H1, and sterol 24-c-methyltransferase (SMT). To facilitate the oligomerization process, pentameric and trimeric coiled-coil domains were employed. RpfE, a resuscitation-promoting factor of Mycobacterium tuberculosis, was added to induce strong immune responses. Pentameric and trimeric coiled-coil domains as well as eight immunodominant epitopes from antigenic proteins of Leishmania infantum, the causative agent of VL, were joined together using appropriate linkers. High-quality 3D structure of monomeric and oligomeric structures followed by refinement and validation processes demonstrated that the designed nanovaccine could be considered to be a promising medication against the parasite; however, experimental validation is essential to confirm the effectiveness of the nanovaccine.

Designing Self-Assembling Chimeric Peptide Nanoparticles with High Stability for Combating Piglet Bacterial Infections.

As a novel type of antibiotic alternative, peptide‐based antibacterial drug shows potential application prospects attributable to their unique mechanism for lysing the membrane of pathogenic bacteria. However, peptide‐based antibacterial drugs suffer from a series of problems, most notably their immature stability, which seriously hinders their application. In this study, self‐assembling chimeric peptide nanoparticles (which offer excellent stability in the presence of proteases and salts) are constructed and applied to the treatment of bacterial infections. In vitro studies are used to demonstrate that peptide nanoparticles NPs1 and NPs2 offer broad‐spectrum antibacterial activity and desirable biocompatibility, and they retain their antibacterial ability in physiological salt environments. Peptide nanoparticles NPs1 and NPs2 can resist degradation under high concentrations of proteases. In vivo studies illustrate that the toxicity caused by peptide nanoparticles NPs1 and NPs2 is negligible, and these nanoparticles can alleviate systemic bacterial infections in mice and piglets. The membrane permeation mechanism and interference with the cell cycle differ from that of antibiotics and mean that the nanoparticles are at a lower risk of inducing drug resistance. Collectively, these advances may accelerate the development of peptide‐based antibacterial nanomaterials and can be applied to the construction of supramolecular nanomaterials.

Fabrication of self-assembled peptide nanoparticles for in vitro assessment of cell apoptosis pathway and in vivo therapeutic efficacy.

Near-infrared fluorescent (NIRF) dye-coupled self-assembled RGD-linked proapoptotic peptide nanoparticles have been synthesizedwith spherical shape and size ~ 30-40nm diameters. The peptide sequence was coupled with cyanine 5.5 probe as NIRF-dye to introduce optical imaging properties and pH-dependent method was used to design Cy5.5 coupled self-assembled peptide nanoparticles (f-SAPNs). Thisnanoprobe has the ability to target αvβ3-integrin receptor overexpressed on cancer cell's surface with improved internalization capabilities into the mitochondria. Thein situstudy showed that this peptide sequence has potential to disrupt the mitochondrial membrane efficiently, activating the Caspase-3 enzyme, and ultimately induces cell apoptosis. It has been observed from in vitro study that the degree of apoptosis for f-SAPNs was increased from 25.6% to 96.3%, while decreased degree of necrosis from 51.7% to 0.2% compared with its parent peptide analog (Cy5.5-c[RGDKLAK]; f-CP)occurs. Further investigations revealed that these f-SAPNs showed high uptake in U87MG glioblastoma cells in comparison with PC-3 prostate cancer cells. Moreover, in vivo therapeutic studies represented the prominent decrease in the size of tumor tissue treated with f-CP and f-SAPNs (201 ± 13 mm3 and 104 ± 6 mm3, respectively) compared with untreated tumor tissues (366 ± 18 mm3). These outcomes highlighted the specificity, and efficacy of f-SAPNs toward αvβ3-integrin expressing tumor tissue in vivoand suggested that these novel designed f-SAPNs may serve as a potential theranostic drug for brain tumor glioblastoma multiforme. The pH-sensitive method gives NIRF dye-coupled self-assembled peptide nanoparticle (f-SAPNs), enables the tunable synthesis of spherical nanoparticles with high stability towards proteolysis, improved biocompatibility, and promising therapeutic efficacy.

Hybridization of tumor homing and mitochondria-targeting peptide domains to design novel dual-imaging self-assembled peptide nanoparticles for theranostic applications.

A novel hybridized dual-targeting peptide-based nanoprobe was successfully designed by using the cyclic heptapeptide. This peptide has Arg-Gly-Asp-Lys-Leu-Ala-Lys sequence, in which the RGD homing motif and KALK mitochondria-targeting motif were linked via amide bond. The designed peptide probe was further modified through covalent linkage to induce dual-imaging functionality, and self-assembled to form spherical nanoparticles. The novel Cy5.5-SAPD-99mTc nanoparticles were tested for in vitro cytotoxicity, cellular uptake, and apoptosis-inducing functionalities. The cellular internalization, enhanced cytotoxicity and selective receptor binding capabilities against U87MG cells, excellent dual-imaging potential, improved apoptosis-inducing feature by damaging mitochondria, and in vivo preclinical investigations suggested that our newly designed novel hybridized peptide-based dual-imaging nanoparticles may serve as an admirable theranostic probe to treat brain tumor glioblastoma multiforme. This study describes the development of dual-targeting self-assembled peptide nanoparticles followed by modifications using NIRF dye and radiolabeled with 99mTc for dual-imaging and enhanced therapeutic efficacy against brain tumor.

High-Loading Self-Assembling Peptide Nanoparticles as a Lipid-Free Carrier for Hydrophobic General Anesthetics.

PurposeTypical hydrophobic amino acids (HAAs) are important motifs for self-assembling peptides (SAPs), but they lead to low water-solubility or compact packing of peptides, limiting their capacity for encapsulating hydrophobic drugs. As an alternative, we designed a peptide GQY based on atypical HAAs, which could encapsulate hydrophobic drugs more efficiently. Although hydrophobic general anesthetics (GAs) have been formulated as lipid emulsions, their lipid-free formulations have been pursued because of some side effects inherent to lipids. Using GAs as targets, potential application of GQY as a carrier for hydrophobic drugs was evaluated.MethodsThioflavin-T (ThT) binding test, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to examine the self-assembling ability of GQY. Pyrene and 8-Anilino-1-naphthalenesulfonic acid (ANS) were used to confirm formation of hydrophobic domain in GQY nanoparticles. Using pyrene as a model, GQY’s capacity to encapsulate hydrophobic drugs was evaluated. GAs including propofol, etomidate and ET26 were encapsulated by GQY. Loss of righting reflex (LORR) test was conducted to assess the anesthetic efficacy of these lipid-free formulations. Paw-licking test was used to evaluate pain-on-injection of propofol-GQY (PROP-GQY) formulation. Hemolytic and cytotoxicity assay were used to evaluate biocompatibility of GQY.ResultsStable nanoparticles containing plenty of hydrophobic cavities could be formed by GQY, which could encapsulate hydrophobic drugs at very high concentration and form stable suspensions. Propofol, etomidate and ET26 formulated by GQY showed anesthetic efficacy comparable to their currently available formulations. Unlike clinic lipid emulsion, PROP-GQY formulation did not cause pain-on-injection in rats. Neither obvious cytotoxicity nor hemolytic activity of GQY was observed.ConclusionGQY could encapsulate GAs to obtain stable and effective formulations. As a lipid-free carrier, GQY exhibited considerable biocompatibility and other side benefits such as reducing pain-on-injection. More SAPs based on atypical HAAs could be designed as promising carriers for hydrophobic drugs.

Emerging self-assembling peptide nanomaterial for anti-cancer therapy.

Recently it is mainly focused on anti-tumor comprehensive treatments like finding target tumor cells or activating immune cells to inhibit tumor recurrence and metastasis. At present, chemotherapy and molecular-targeted drugs can inhibit tumor cell growth to a certain extent. However, multi-drug resistance and immune escape often make it difficult for new drugs to achieve expected effects. Peptide hydrogel nanoparticles is a new type of biological material with functional peptide chains as the core and self-assembling peptide (SAP) as the framework. It has a variety of significant biological functions, including effective local inflammation suppression and non-drug-resistant cell killing. Besides, it can induce immune activation more persistently in an adjuvant independent manner when compared with simple peptides. Thus, SAP nanomaterial has great potential in regulating cell physiological functions, drug delivery and sensitization, vaccine design and immunotherapy. Not only that, it is also a potential way to focus on some specific proteins and cells through peptides, which has already been examined in previous research. A full understanding of the function and application of SAP nanoparticles can provide a simple and practical strategy for the development of anti-tumor drugs and vaccine design, which contributes to the historical transition of peptide nanohydrogels from bench to bedside and brings as much survival benefits as possible to cancer patients.

Self-assembled peptide nanoparticles for enhanced dark-field hyperspectral imaging at the cellular and invertebrate level

Enhanced dark-field hyperspectral imaging (EDF-HSI) integrates advanced spectroscopy and imaging techniques, enabling fast and quantitative insights into the interactions between nanomaterials and organisms at the cellular or invertebrate level. However, the usage of biomolecule-based nanomaterials as contrast agents for EDF-HSI is highly challenging because these nanomaterials usually lack the characteristic optical scattering properties that can be readily distinguished from the scattering signals of organisms. Herein, we report peptide nanoparticles fabricated through covalent self-assembly of dipeptides and genipin for EDF-HSI in vitro and in vivo. Two dipeptides with either C-terminal amidation or not were used as the building blocks for covalent self-assembly. Significantly, the optical scattering intensity of the resulting nanoparticles is enhanced by the amidation. The amidation also enhances the stability of the peptide nanoparticles both in solutions and inside cells or organisms due to inhibition of electrostatic repulsion among the building blocks. Therefore, the nanoparticles fabricated from the dipeptide with uncharged C-terminal amide can be facilely visualized and tracked inside cells and nematodes through EDF-HSI. These results demonstrate that peptide nanomaterials can be endowed with optical scattering properties suitable for EDF-HSI, providing a promising approach for visualization and analysis of the activities of biomaterials in vitro and in vivo.

Antibacterial activities of physiologically stable, self-assembled peptide nanoparticles.

In this study, we report that host defense protein-derived ten amino acid long disulfide-linked peptides self-assemble in the form of β-sheets and β-turns, and exhibit concentration-dependent self-assembly in the form of nanospheres, termed as disulfide linked nanospheres (DSNs). As expected, bare DSNs are prone to aggregation in ionic solutions and in the presence of serum proteins. To yield physiologically stable self-assembled peptide-based materials, DSNs are stabilized in the form of supramolecular assemblies using β-cyclodextrins (β-CD) and fucoidan, as delivery carriers. The inclusion complexes of DSNs with β-CD (β-CD-DSN) and electrostatic complexation of fucoidan with DSNs (FC-DSN) stabilizes the secondary structure of DSNs. Comparison of β-CD-DSNs with FC-DSNs reveals that inclusion complexes of DSNs formed in the presence of β-CD are highly stable under physiological conditions, show high cellular uptake, exhibit bacterial flocculation, and enhance antibacterial efficacies of DSNs in a range of Gram-positive and Gram-negative bacteria.

Multifunctional self-assembled peptide nanoparticles for multimodal imaging-guided enhanced theranostic applications against glioblastoma multiforme.

The synthesis of self-assembled peptide nanoparticles using a facile one-pot synthesis approach is gaining increasing attention, allowing therapy in combination with diagnosis. Their drawback is limited diagnostic potential, which can be improved after necessary modifications and efficacious functionalization. Herein, a cyclic heptapeptide having the Arg-Gly-Asp-Lys-Leu-Ala-Lys sequence was modified by conjugation of the ε-amino group of the terminal lysine residue with diethylenetriamine pentaacetic acid (DTPA) as a bifunctional chelating agent (BFC) for radiolabeling with a γ-emitting radionuclide (99mTc, half-life 6.01 h; energy 140 keV). Further, the free amino group of the middle lysine residue was successfully conjugated with near-infrared fluorescence (NIRF) dye Cyanine5.5 N-succinimidyl ester (Ex/Em = 670/701 nm) by a co-assembly method to form newly designed novel NIRF dye conjugated self-assembled peptide–DTPA (Cy5.5@SAPD) nanoparticles. The fluorescent nanoparticle formation was confirmed by using a fluorescence spectrophotometer (Ex/Em = 650/701 nm), and the transmission electron microscope (TEM) images showed a size of ∼ 40 nm with a lattice fringe distance of 0.294 nm. Cytotoxicity and confocal laser scanning microscopy (CLSM) studies showed that these nanoparticles possess a high affinity for the αvβ3-integrin receptor overexpressed on brain tumor glioblastoma with an EC50 = 20 μM. Moreover, these nanoparticles were observed to have potential to internalize into U87MG cells more prominently than HEK-293 cancer cells and induce apoptosis. The apoptosis assay showed 79.5% apoptotic cells after 24 h treatment of Cy5.5@SAPD nanoparticles. Additionally, these nanoparticles were also radiolabeled with 99mTc for the single photon emission computed tomography (SPECT) imaging study in tumor-bearing female Balb/c mice. The excellent imaging feature of Cy5.5@SAPD-99mTc nanoparticles as a multimodal (SPECT/NIRF) diagnostic probe, as well as noteworthy therapeutic potential was observed. The results suggested that our newly designed novel dual-targeting dual-imaging nanoparticles may serve as an admirable theranostic probe to treat brain tumor glioblastoma multiforme.

Self-assembled peptide nanoparticles with endosome escaping permits for co-drug delivery

The diagnosis and treatment of major diseases, especially tumors, was the key to improving the cure rate and survival rate of patients. Therefore, one of the main goals of modern medicine was to develop effective, non-toxic treatments. This paper successfully established dipeptide nanoparticles/clofarabine/aptamer AS1411/influenza hemagglutinin peptide/siRNA/doxorubicin (DNPs/Clolar/AS1411/HA/RNA/DOX) multi-functional nanoparticles for specific delivery, cancer treatment and bioimaging. It was an ideal choice for multi-drug synergy treatment. First, non-toxic DNPs formed by self-assembly of dipeptides with safe and biocompatible effect. Second, from the perspective of the multi-functional nanoparticles for nano-drug tumors imaging monitoring, AS1411 and HA were used as cell permits for enhancing the specificity of cell drug delivery ability and improving the endosomal escape, respectively. Third, the multi-functional nanoparticles with Clolar, siRNA and DOX, three drug synergistic treatments were used to improve the therapeutic effect of tumors. Both cell experiments and vivo experiments demonstrated that the synergistic treatment of the multi-drugs was superior to the effect of single-drug therapy. Thus, the proposed multi-functional nanoparticles have initiated new ideas for these hybrid anticancer drugs based on peptide self-assembled nanocarriers and its widely applications in biomedicine.

Self-assembled peptide nanoparticles for efficient delivery of methotrexate into cancer cells

The low cellular uptake of Methotrexate (MTX), a commonly used anticancer drug, is a big challenge for efficient cancer therapy. Self-assembled peptide nanoparticles (SAPNs) are one of the major classes of peptide vectors that have gained much attention toward novel drug delivery systems. In the present study, different sequences of cell-penetrating peptides including R2W4R2 and W3R4W3 and their SAPNs (R2W4R2-E12 and W3R4W3-E12) were designed for efficient delivery of MTX into MCF7 breast cancer cells. Based on electron microscopy results, the obtained SAPNs were in nano scale with spherical shape. There was a positive relationship between the free energy of water to octanol transferring and cellular penetration of designed nanostructures. The R2W4R2 possessed proper free energy and ability to form a spherical structure and hydrophobic–hydrophobic interactions, therefore, exhibited more cellular penetration than W3R4W3. The cellular uptake of obtained nanoparticles was examined by flow cytometry and fluorescence microscopy, in which, R2W4R2 and R2W4R2-E12 showed more appropriate penetration into MCF7 cells than W3R4W3 and W3R4W3-E12. The cytotoxicity of MTX-loaded peptides and SAPNs was examined by MTT assay. As a result, at higher concentrations, the R2W4R2 and R2W4R2-E12 showed higher cytotoxic behavior than their counterparts. Despite their enhanced cellular internalization, the cytotoxic behavior of MTX-loaded SAPNs at lower concentrations was relatively less than free MTX, which could be ascribed to the gradual nature of drug detachment from these conjugates. Therefore, R2W4R2 could be considered as an efficient choice to enhance the therapeutic efficiency of MTX in cancer treatments.

Self-assembled peptide nanoparticles responsive to multiple tumor microenvironment triggers provide highly efficient targeted delivery and release of antitumor drug

Stimuli-responsive drug delivery systems based on tumor microenvironment conditions show tremendous promise to enhance tumor-targeted delivery and drug release. Herein, a multifunctional peptide (P51) was developed for programmed delivery of the hydrophobic chemotherapeutic agent pirarubicin. P51 was prepared with a ligand-specific targeting for the cancer biomarker Arg-Gly-Asp (RGD), and three tumor microenvironment-sensitive release triggers, acid environment, reducing agent, and a specific enzyme. The peptides Cys-s-s-Cys (disulfide linkage) and Pro-Val-Gly-Leu-Ile-Gly correspond to the cleavage sites of a reducing agent (DTT) and an enzyme (MMP-2). The peptides act as a junction between Ser-Glu-Glu-Asp-Pro (a negatively charged sequence) and a 41-residue peptide containing an α-helix that has the capacity to encapsulate pirarubicin via electrostatic and hydrophobic interactions. These interactions can be disrupted by the acidic tumor microenvironment. Self-assembly of P51 and pirarubicin (P51-THP NPs) results into stable spherical nanoparticles in a single step. We have demonstrated that the acid environment, DTT, and MMP-2 stimulate the release of pirarubicin from P51-THP NPs and, more importantly, the efficiency of drug release is markedly increased when all three release triggers are present. In addition, more effective tumor targeting, antitumor effect, and reduced systemic toxicity of P51-THP NPs have been confirmed by in vitro and in vivo results.

Designing self-assembled peptide nanovaccine against Streptococcus pneumoniae: An in silico strategy

Streptococcus pneumoniae is the main cause of diseases such as meningitis, pneumoniae and sepsis, especially in children and old people. Due to costly antibiotic treatment, and increasing resistance of pneumococcus, developing high-efficient protective vaccine against this pathogen is an urgent need. Although the pneumoniae polysaccharide vaccine (PPV) and pneumonia conjugate vaccines (PCV) are the efficient pneumococcal vaccine in children and adult groups, but the serotype replacement of S. pneumoniae strains causes the reduction in efficacy of such vaccines. For overcoming the aforesaid drawbacks epitope-based vaccines are introduced as the relevant alternative. In our previous research, the epitope vaccine was designed based on immunodominant epitopes from PspA, CbpA antigens as cellular stimulants and PhtD, PiuA as humoral stimulants. Because the low immunogenicity is the main disadvantage of epitope vaccine, in the current study, we applied coiled-coil self-assembled structures for developing our vaccine. Recently, self-assembled peptide nanoparticles (SAPNs) have gained much attention in the field of vaccine development due to their multivalency, self-adjuvanticity, biocompatibility, and size similarity to pathogen. In this regard, the final designed vaccine is comprised of cytotoxic T lymphocytes (CTL) epitopes from PspA and CbpA, helper T lymphocytes (HTL) epitopes from PhtD and PiuA, the pentamer and trimmer oligomeric domains form 5-stranded and 3-stranded coiled-coils as self-assembled scaffold, Diphtheria toxoids (DTD) as a universal T-helper, which fused to each other with appropriate linkers. The four different arrangements based on the order of above-mentioned compartments were constructed, and each of them were modeled, and validated to find the 3D structure. The structural, physicochemical, and immunoinformatics analyses of final vaccine construct represented that our vaccine could stimulate potent immune response against S. pneumoniae; however, the potency of that should be approved via various in vivo and in vitro immunological tests.

Preparation and printability of ultrashort self-assembling peptide nanoparticles.

Nanoparticles (NPs) have left their mark on the field of bioengineering. Fabricated from metallic, magnetic, and metal oxide materials, their applications include drug delivery, bioimaging, and cell labeling. However, as they enter the body, the question remains – where do they go after fulfilling their designated function? As most materials used to produce NPs are not naturally found in the body, they are not biodegradable and may accumulate overtime. There is a lack of comprehensive, long-term studies assessing the biodistribution of non-biodegradable NPs for even the most widely studied NPs. There is a clear need for NPs produced from natural materials capable of degradation in vivo. As peptides exist naturally within the human body, their non-toxic and biocompatible nature comes as no surprise. Ultrashort peptides are aliphatic peptides designed with three to seven amino acids capable of self-assembling into helical fibers within macromolecular structures. Using a microfluidics flow-focusing approach, we produced different peptide-based NPs that were then three-dimensional (3D) printed with our novel printer setup. Herein, we describe the preparation method of NPs from ultrashort self-assembling peptides and their morphology in both manual and 3D-printed hydrogels, thus suggesting that peptide NPs are capable of withstanding the stresses involved in the printing process.

Application of built-in adjuvants for epitope-based vaccines.

Several studies have shown that epitope vaccines exhibit substantial advantages over conventional vaccines. However, epitope vaccines are associated with limited immunity, which can be overcome by conjugating antigenic epitopes with built-in adjuvants (e.g., some carrier proteins or new biomaterials) with special properties, including immunologic specificity, good biosecurity and biocompatibility, and the ability to vastly improve the immune response of epitope vaccines. When designing epitope vaccines, the following types of built-in adjuvants are typically considered: (1) pattern recognition receptor ligands (i.e., toll-like receptors); (2) virus-like particle carrier platforms; (3) bacterial toxin proteins; and (4) novel potential delivery systems (e.g., self-assembled peptide nanoparticles, lipid core peptides, and polymeric or inorganic nanoparticles). This review primarily discusses the current and prospective applications of these built-in adjuvants (i.e., biological carriers) to provide some references for the future design of epitope-based vaccines.

Abstract 4649: Targeting the cancer cell lysosome with transformable self-assembling peptide nanoparticles

Abstract Lysosome-mediated cell death has recently become of great interest to the cancer community as several compounds have been shown to preferentially induce cancer cell death via lysosomal membrane permeabilization (LMP) (e.g., oleocanthal, salinomycin, and TiO2 nanoparticles). Further, many cancer cell lines that are resistant to traditional cancer therapeutics are highly susceptible to lysosome-mediated cell death. Here, we develop transformable peptide nanoparticles (NP) designed to traffic to cancer cell lysosomes, form aggregates, and induce LMP. The peptide consists of three motifs: 1) a hydrophilic, cell penetrating, and pH-responsive poly-d-Arg motif, 2) a hydrogen-bonding motif derived from beta amyloid (KLVFF); and 3) hydrophobic bis(pyrene) that fluoresces upon aggregation. The peptides initially self-assemble into NPs (50nm via TEM) in PBS, but when exposed to a lysosomal pH of 4.5, form much larger aggregates. We show that these nanoaggregates colocalize with the lysosome, leading to cell death, suggesting the induction of LMP. Moreover, utilizing bis(pyrene) we show that while these aggregates form in the lung carcinoma cell line, A549, they do not form in 3T3 fibroblasts. Additionally, we demonstrate that these nanoaggregates are highly toxic to A549 cells with IC50 in the low micromolar range (~2μM). This offers a novel organelle-specific strategy to preferentially target and kill cancer cells. Citation Format: Christopher M. Baehr, Lei Wang, Kit S. Lam. Targeting the cancer cell lysosome with transformable self-assembling peptide nanoparticles [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4649.

TAT-modified self-assembled cationic peptide nanoparticles as an efficient antibacterial agent

The increasing emergence of drug resistant pathogenic bacteria poses a great challenge to clinical therapy and a threat to public health. Cationic peptides have received great attention for their unique antibacterial mechanism and ability to combat drug-resistant bacteria. In this study, we designed a TAT-modified cationic peptide PA-28 which self-assembled into nanoparticles of about 150 nm. These nanoparticles showed strong antimicrobial activities against both gram-positive and gram-negative bacteria, including drug-resistant bacteria. They were more potent than the unassembled counterpart peptide nonalysine (K9). Their antibacterial mechanism of directly destructing bacterial wall/membrane reduces the possibility of developing bacterial resistance. In vivo anti-infective experiments showed that these nanoparticles were able to penetrate the blood–brain barrier to inhibit bacterial growth in infected brains of rats. In addition, these nanoparticles induced low hemolysis below the minimum inhibitory concentration. Therefore, the peptide designed in this study is a promising and efficient antibacterial agent against bacterial infections.