Bioengineered yeast-derived vacuoles with enhanced tissue-penetrating ability for targeted cancer therapy

Engineered Microorganisms for Advancing Tumor Therapy

Engineered microorganisms have attracted significant interest as a unique therapeutic platform in tumor treatment. Compared with conventional cancer treatment strategies, engineering microorganism-based systems provide various distinct advantages, such as the intrinsic capability in targeting tumors, their inherent immunogenicity, in situ production of antitumor agents, and multiple synergistic functions to fight against tumors. Herein, the design, preparation, and application of the engineered microorganisms for advanced tumor therapy are thoroughly reviewed. This review presents a comprehensive survey of innovative tumor therapeutic strategies based on a series of representative engineered microorganisms, including bacteria, viruses, microalgae, and fungi. Specifically, it offers extensive analyses of the design principles, engineering strategies, and tumor therapeutic mechanisms, as well as the advantages and limitations of different engineered microorganism-based systems. Finally, the current challenges and future research prospects in this field, which can inspire new ideas for the design of creative tumor therapy paradigms utilizing engineered microorganisms and facilitate their clinical applications, are discussed.

Synergistic vesicle-vector systems for targeted delivery

With the immense progress in drug delivery systems (DDS) and the rise of nanotechnology, challenges such as target specificity remain. The vesicle-vector system (VVS) is a delivery system that uses lipid-based vesicles as vectors for a targeted drug delivery. When modified with target-probing materials, these vesicles become powerful vectors for drug delivery with high target specificity. In this review, we discuss three general types of VVS based on different modification strategies: (1) vesicle-probes; (2) vesicle-vesicles; and (3) genetically engineered vesicles. The synthesis of each VVS type and their corresponding properties that are advantageous for targeted drug delivery, are also highlighted. The applications, challenges, and limitations of VVS are briefly examined. Finally, we share a number of insights and perspectives regarding the future of VVS as a targeted drug delivery system at the nanoscale.

Reassembled Vacuoles for Drug Delivery Carriers Using Yeast Vacuoles for Enhanced Antibacterial Activity

In this study, we aimed to develop an efficient drug delivery system by reassembling vacuoles isolated from Saccharomyces cerevisiae. Initially, we assessed the impact of vacuolar enzymes on the efficacy of the loaded antibiotic polymyxin B (PMB), by conducting antibacterial activity tests using Shigella flexneri and Salmonella enteritidis. The results showed that vacuolar enzymes inhibited the effectiveness of PMB, highlighting the limitations of using natural vacuoles as drug carriers. To overcome this, we proposed a new drug delivery system called reassembled vacuoles (ReV). ReV particles were created by removing vacuolar enzymes and reassembling the vacuolar membrane through extrusion. ReV demonstrated improved structural stability, a more uniform size, and enhanced PMB release compared to natural vacuoles. Encapsulation efficiency tests revealed high loading efficiency for both normal vacuoles (NorV) and ReV, with over 80% efficiency at concentrations up to 600 μg/mL. The antibacterial activity of PMB-loaded ReV showed comparable results to PMB alone, indicating the potential of ReV as a drug delivery system. In conclusion, reassembled vacuoles offer a promising approach for drug delivery, addressing the limitations of natural vacuoles and providing opportunities for targeted and efficient drug release.

Cellular organelles as drug carriers for disease treatment

Organelles not only constitute the basic structure of the cell but also are important in maintaining the normal physiological activities of the cell. With the development of biomimetic nanoscience, researchers have developed technologies to use organelles as drug carriers for disease treatment. Compared with traditional drug carriers, organelle drug carriers have the advantages of good biocompatibility, high drug loading efficiency, and modifiability, and the surface biomarkers of organelles can also participate in intracellular signal transduction to enhance intracellular and intercellular communication, and assist in enhancing the therapeutic effect of drugs. Among different types of organelles, extracellular vesicles, lipid droplets, lysosomes, and mitochondria have been used as drug carriers. This review briefly reviews the biogenesis, isolation methods, and drug-loading methods of four types of organelles, and systematically summarizes the research progress in using organelles as drug-delivery systems for disease treatment. Finally, the challenges faced by organelle-based drug delivery systems are discussed. Although the organelle-based drug delivery systems still face challenges before they can achieve clinical translation, they offer a new direction and vision for the development of next-generation drug carriers.

Yeast vacuolar enzymes as novel hatching inhibitors for aquatic organisms, Daphnia magna and Danio rerio eggs

Concerns over the spread of non-native species in aquatic environments have led to the need for effective methods to prevent and control their spread while protecting native species. This study investigated the potential of yeast vacuolar enzymes as a natural hatching inhibitor for controlling aquatic organisms. Hatching experiments with Daphnia magna eggs demonstrated that exposure to yeast vacuole enzymes inhibited hatching in a concentration-dependent manner, suggesting their potential as an effective inhibitor of egg hatching in aquatic organisms. Interestingly, the protease used for comparative purposes did not inhibit hatching, but instead increased the mortality of hatched D. magna. Additionally, chorionic changes were observed in non-hatched D. magna eggs and zebrafish eggs exposed to yeast vacuole enzymes, suggesting that the enzyme can alter the chorion and interfere with hatching. These findings suggest that yeast vacuolar enzymes may be a promising and natural management tool for controlling the spread of harmful aquatic organisms, and further research is warranted to explore their potential for species-specific control.

Inducing a Proinflammatory Response with Bioengineered Yeast Vacuoles with TLR2-Binding Peptides (VacT2BP) as a Drug Carrier for Daunorubicin Delivery

Immune adjuvants have roles in immune activation for cancer therapy, and adjuvants derived from microbes have been applied. In this study, we propose the use of bioengineered vacuoles, derived from recombinant yeast with acute myeloid leukemia (AML) specificity and having a TLR-2-binding peptide (VacT2BP) on their surface, to induce a proinflammatory response as a dual-function nanomaterial for daunorubicin (DNR) delivery. Our results demonstrate that nanosized, isolated VacT2BP induced HL-60 cell-specific DNR delivery and apoptosis. Furthermore, we observed the selective release of high-mobility group box 1 from apoptotic HL-60 cells by DNR@VacT2BP. We concluded that DNR@VacT2BP exhibited target selectivity, and the indiscriminate occurrence of damage-associated molecular patterns (DAMPs) was inhibited by the VacT2BP carrier. The therapeutic efficacy of DNR@VacT2BP was confirmed in AML xenograft mice, with about 82% tumor growth inhibition. Following drug delivery, apoptotic cells and DAMPs with residual VacT2BP (apopDNR@VacT2BP) upregulated the proinflammatory immune response of macrophages. In addition, apopDNR@VacT2BP enhanced phagocytosis activity. Macrophages stimulated by apopDNR@VacT2BP suppressed cancer proliferation by about 40%. In summary, our results suggest that dual-functional vacuoles with a target-specific peptide can be a potential strategy for selective drug delivery and construction of an immune environment to fight cancer, thereby improving prognosis.

Targeted Killing of Staphylococcus aureus Using Specific Peptides Displayed on Yeast Vacuoles

Staphylococcus aureus is a common pathogen that causes health care-related and community-associated infections. In this study, we provide a novel system that can recognize and kill S. aureus bacteria. The system is specifically based on a combination of the phage display library technique and yeast vacuoles. A phage clone displaying a peptide capable of specific binding to a whole S. aureus cell was selected from a 12-mer phage peptide library. The peptide sequence was SVPLNSWSIFPR. The selected phage's ability to bind specifically with S. aureus was confirmed using an enzyme-linked immunosorbent assay, and the chosen peptide was then synthesized. The results showed that the synthesized peptides displayed high affinity with S. aureus but low binding ability with other strains, including Gram-negative and Gram-positive bacteria such as Salmonella sp., Shigella spp., Escherichia coli, and Corynebacterium glutamicum. In addition, yeast vacuoles were used as a drug carrier by encapsulating daptomycin, a lipopeptide antibiotic used to treat Gram-positive bacterial infections. The expression of specific peptides at the encapsulated vacuole membrane created an efficient system that can specifically recognize and kill S. aureus bacteria. IMPORTANCE The phage display method was used to select peptides with high affinity and specificity for S. aureus, and these peptides were then induced to be expressed on the surface of yeast vacuoles. These surface-modified vacuoles can act as drug carriers, with drugs such as the lipopeptide antibiotic daptomycin loaded inside. An advantage of using yeast vacuoles as a drug carrier is that they can be easily produced through yeast culture, making the approach cost-effective and suitable for large-scale production and potential implementation in clinical settings. This novel approach offers a promising way to specifically target and eliminate S. aureus that could ultimately lead to improved treatment of bacterial infections and reduced risk of antibiotic resistance.

Tumor-targeted exosomes for delivery of anticancer drugs

Exosomes are small phospholipid bilayer vesicles that are naturally produced by all living cells, both prokaryotes and eukaryotes. The exosomes due to their unique size, reduced immunogenicity, and their ability to mimic synthetic liposomes in carrying various anticancer drugs have been tested as drug delivery vehicles for cancer treatment. An added advantage of developing exosomes as a drug carrier is the ease of manipulating their intraluminal content and their surface modification to achieve tumor-targeted drug delivery. In the past ten-years, there has been an exponential increase in the number of exosome-related studies in cancer. Preclinical studies demonstrate exosomes-mediated delivery of chemotherapeutics, biologicals and natural products produce potent anticancer activity both, in vitro and in vivo. In contrast, the number of exosome-based clinical trials are few due to challenges in the manufacturing and scalability related to large-scale production of exosomes and their storage and stability. Herein, we discuss recent advances in exosome-based drug delivery for cancer treatment in preclinical and clinical studies and conclude with challenges to be overcome for translating a larger number of exosome-based therapies into the clinic.

Yeast-derived vacuoles as a novel carrier with enhanced hCMEC/D3 cell monolayer penetration

The blood-brain barrier (BBB) is a brain protection structure that restricts drug delivery from the blood to the central nervous system. Thus, we developed a novel drug carrier using yeast vacuoles to overcome this problem. The purpose of this study was to assess the drug transportability of yeast vacuoles using a human cerebral microvascular endothelial cell line (hCMEC/D3) cell monolayer. Here, we used daunorubicin (DNR) as a microtubule-targeting agent with the ability to disaggregate pre-formed fibrils and prevent Tau fibrillization. An in vitro model was developed by culturing hCMEC/D3 cells on Transwell inserts in EBM-2 endothelial basal medium until the cells formed a monolayer. Next, nano-sized yeast vacuoles were loaded with DNR, and the signals inside and outside the hMEC/D3 cell monolayer were detected using the GloMax^® Explorer fluorometer. DNR penetrated the cell monolayer and was regulated by endocytosis via receptor-mediated macropinocytosis on the surface of the cell. Confocal imaging showed a significant increase in intracellular DNR fluorescence when the cells were treated with the vacuole-encapsulated drug. These results indicate that the drug penetrated the hCMEC/D3 cell monolayer via encapsulation into the vacuoles. Overall, yeast-derived vacuoles are promising candidates as drug carriers to the brain.

Identification of TLR2/4-mediated phagocytosis and immune response activation pathways by vacuoles isolated from Saccharomyces cerevisiae

The vacuoles of the yeast Saccharomyces cerevisiae are closely related to mammalian lysosomes and play a role in macromolecular degradation due to the hydrolytic enzymes present inside. The vacuoles also regulate osmotic pressure and control cellular homeostasis. In previous results, vacuoles were shown to activate the immune response of macrophages by promoting the production of immune-mediated transporters nitric oxide (NO), reactive oxygen species (ROS), and pro-inflammatory cytokines. In this study, the effects of vacuoles on the phagocytosis activity of RAW264.7 cells and their potential as immune enhancers were evaluated, and receptors capable of recognizing vacuoles were examined. An investigation using the phagocytes assay showed that phagocytosis activity increased by the vacuole. Besides, after treatment with TLR2/4 inhibitor, the expression of pro-inflammatory cytokines by vacuoles was significantly reduced and the inducible nitric oxide synthase (iNOS) protein was also significantly reduced. However, treatment with a TLR2 inhibitor did not reduce the production of interleukin-6 (IL)-6, a pro-inflammatory cytokine. As a result of confirming the activation of TLR2/4 using Western blot and immunofluorescence (IF), the TLR2/4 protein expression and fluorescence intensity increased depending on the concentration of vacuoles. Yeast vacuoles significantly upregulate protein expression of p-p65/p-p38 MAPKs. In summary, the vacuoles isolated from S. cerevisiae in macrophages have increased phagocytic ability at a concentration of 20 (µg/ml) and can function as immune-enhancing agent suggesting that TLR2/4 mediated the p38 MAPK/nuclear factor kappa B signaling pathway.

Surface-modified vacuole-based daunorubicin delivery system for acute myeloid leukaemia (AML) and their selective therapeutics

The vacuoles in Saccharomyces cerevisiae are the key players digesting the waste within the cell. This functional organelle corresponding to the lysosome of mammalians contains acidic hydrolases and specific membrane proteins. Vacuoles have more than 60 hydrolytic enzymes and can easily be modified by genetic engineering. In previous study, we optimised the encapsulation condition with appropriate time and concentration and confirmed the use of vacuole as drug delivery carrier for acute myeloid leukaemia treatment. In this study, recombinant vacuole that could target the acute myeloid leukaemia cell line was constructed. The vacuoles derived from genetic engineered yeast were decorated with targeting peptide that has specific affinity with TLR2 on AML cell membrane. The anti-cancer efficacy of AML targeting vacuoles carriers with encapsulated daunorubicin was shown to be higher than normal vacuole carriers and the crude daunorubicin. The results confirmed that target selective chemotherapy using the vacuole drug delivery system is effective and offers potential for cancer therapy.

Melanin Treatment Effect of Vacuoles-Zinc Oxide Nanoparticles Combined with Ascorbic Acid

Currently, ascorbic acid (AA) is widely used as a skin whitening material, but, AA, an unstable hydrophilic molecule, cannot penetrate the skin easily, due to the hydrophobic character of the stratum corneum. Therefore, we conjugated AA with hydrated zinc oxide-an inorganic matrix with positive surface charge, to improve the stability of AA. The metal-conjugated-ascorbic acid (ZnAA) was then combined with yeast vacuole through the vacuolar membrane proteins that relate to metal transportation to create an enhanced vacuole that contained ZnAA. The characteristics of vacuole with ZnAA (ZnAA_Vac) were next examined by various tests that included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray (EDX) analysis. Furthermore, the ability of ZnAA_Vac to degrade melanin was confirmed in both melanoma cell line B16F10, and the artificial human skin MelanoDerm. The results showed that ZnAA_Vac possessed a higher depigmenting effect than the wild-type vacuole or ascorbic acid by reducing 75% of melanin color. Interestingly, ZnAA_Vac was found to be harmless, and did not cause any cytotoxicity to the cells. Overall, ZnAA_Vac is expected to provide a robust, harmless, and effective whitening agent for the skin.

The sound of drug delivery: Optoacoustic imaging in pharmacology

Optoacoustic (photoacoustic) imaging offers unique opportunities for visualizing biological function in vivo by achieving high-resolution images of optical contrast much deeper than any other optical technique. The method detects ultrasound waves that are generated inside tissue by thermo-elastic expansion, i.e., the conversion of light absorption by tissue structures to ultrasound when the tissue is illuminated by the light of varying intensity. Listening instead of looking to light offers the major advantage of image formation with a resolution that obeys ultrasonic diffraction and not photon diffusion laws. While the technique has been widely used to explore contrast from endogenous photo-absorbing molecules, such as hemoglobin or melanin, the use of exogenous agents can extend applications to a larger range of biological and possible clinical applications, such as image-guided surgery, disease monitoring, and the evaluation of drug delivery, biodistribution, and kinetics. This review summarizes recent developments in optoacoustic agents, and highlights new functions visualized and potent pharmacology applications enabled with the use of external contrast agents.

Bacterial extracellular vesicles-based therapeutic strategies for bone and soft tissue tumors therapy

Bone and soft tissue tumors are complex mesenchymal neoplasms that seriously endanger human health. Over the past decade, the relationship between microorganisms and human health and diseases is getting more attention. The extracellular vesicles derived from bacteria have been shown to regulate bacterial-host cell communication by transferring their contents, including nucleic acids, proteins, metabolites, lipopolysaccharides, and peptidoglycans. Bacteria extracellular vesicles (BEVs) are promising lipid-bilayer nanocarriers for the treatment of many diseases due to their low toxicity, drug loading capacity, ease of modification and industrialization. Specially, BEVs-based cancer therapy has attracted much attention because of their ability to effectively stimulate immune responses. In this review, we provide an overview of the biogenesis, composition, isolation, classification, and internalization of BEVs. We then comprehensively summarize the sources of BEVs in cancer therapy and the BEVs-related cancer treatment strategies. We further highlight the great potential of BEVs in bone and soft tissue tumors. Finally, we conclude the major advantages and challenges of BEVs-based cancer therapy. We believe that the comprehensive understanding of BEVs in the field of cancer therapy will generate innovative solutions to bone and soft tissue tumors and achieve clinical applications.

Customized materials-assisted microorganisms in tumor therapeutics

Microorganisms have been extensively applied as active biotherapeutic agents or drug delivery vehicles for antitumor treatment because of their unparalleled bio-functionalities. Taking advantage of the living attributes of microorganisms, a new avenue has been opened in anticancer research. The integration of customized functional materials with living microorganisms has demonstrated unprecedented potential in solving existing questions and even conferring microorganisms with updated antitumor abilities and has also provided an innovative train of thought for enhancing the efficacy of microorganism-based tumor therapy. In this review, we have summarized the emerging development of customized materials-assisted microorganisms (MAMO) (including bacteria, viruses, fungi, microalgae, as well as their components) in tumor therapeutics with an emphasis on the rational utilization of chosen microorganisms and tailored materials, the ingenious design of biohybrid systems, and the efficacious antitumor mechanisms. The future perspectives and challenges in this field are also discussed.

Enhanced immune response by vacuoles isolated from Saccharomyces cerevisiae in RAW 264.7 macrophages

Vacuoles are membrane vesicles in eukaryotic cells, the digestive system of cells that break down substances absorbed outside the cell and digest the useless components of the cell itself. Researches on anticancer and intractable diseases using vacuoles are being actively conducted. The practical application of the present study to animals requires the determination of the biocompatibility of vacuole. In the present study, we evaluated the effects of vacuoles isolated from Saccharomyces cerevisiae in RAW 264.7 cells. This showed a significant increase in the production of nitric oxide (NO) produced by macrophage activity. Using Reactive Oxygen Species (ROS) assay, we identified that ROS is increased in a manner dependent on vacuole concentration. Western blot analysis showed that vacuole concentration-dependently increased protein levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2). Therefore, iNOS expression was stimulated to induce NO production. In addition, pro-inflammatory cytokines levels promoted, such as interleukin (IL) 6 (IL-6) and tumor necrosis factor (TNF) α (TNF-α). In summary, vacuoles activate the immune response of macrophages by promoting the production of immune-mediated transporters NO, ROS, and pro-inflammatory cytokines.

Bio-Nanocarriers for Lung Cancer Management: Befriending the Barriers

Lung cancer is a complex thoracic malignancy developing consequential to aberrations in a myriad of molecular and biomolecular signaling pathways. It is one of the most lethal forms of cancers accounting to almost 1.8 million new annual incidences, bearing overall mortality to incidence ratio of 0.87. The dismal prognostic scenario at advanced stages of the disease and metastatic/resistant tumor cell populations stresses the requisite of advanced translational interdisciplinary interventions such as bionanotechnology. This review article deliberates insights and apprehensions on the recent prologue of nanobioengineering and bionanotechnology as an approach for the clinical management of lung cancer. The role of nanobioengineered (bio-nano) tools like bio-nanocarriers and nanobiodevices in secondary prophylaxis, diagnosis, therapeutics, and theranostics for lung cancer management has been discussed. Bioengineered, bioinspired, and biomimetic bio-nanotools of considerate translational value have been reviewed. Perspectives on existent oncostrategies, their critical comparison with bio-nanocarriers, and issues hampering their clinical bench side to bed transformation have also been summarized.

Croconaine-based nanoparticles enable efficient optoacoustic imaging of murine brain tumors

Contrast enhancement in optoacoustic (photoacoustic) imaging can be achieved with agents that exhibit high absorption cross-sections, high photostability, low quantum yield, low toxicity, and preferential bio-distribution and clearance profiles. Based on advantageous photophysical properties of croconaine dyes, we explored croconaine-based nanoparticles (CR780RGD-NPs) as highly efficient contrast agents for targeted optoacoustic imaging of challenging preclinical tumor targets. Initial characterization of the CR780 dye was followed by modifications using polyethylene glycol and the cancer-targeting c(RGDyC) peptide, resulting in self-assembled ultrasmall particles with long circulation time and active tumor targeting. Preferential bio-distribution was demonstrated in orthotopic mouse brain tumor models by multispectral optoacoustic tomography (MSOT) imaging and histological analysis. Our findings showcase particle accumulation in brain tumors with sustainable strong optoacoustic signals and minimal toxic side effects. This work points to CR780RGD-NPs as a promising optoacoustic contrast agent for potential use in the diagnosis and image-guided resection of brain tumors.

Encapsulation of daunorubicin into Saccharomyces cerevisiae-derived lysosome as drug delivery vehicles for acute myeloid leukemia (AML) treatment

Lysosome, an intracellular organelle with an acid interior, contains acidic hydrolases and specific membrane proteins. Saccharomyces cerevisiae contains vacuoles (corresponding to lysosomes) that have similar lipid composition membrane to mammalian cell membrane. However, yeast vacuoles do not cause significant immune stimulation in vivo. Taking advantage of these structural similarities and bio-derived strengths, the present study describes encapsulation of daunorubicin into lysosome derived from S. cerevisiae as drug delivery vehicles for acute myeloid leukemia (AML) treatment. Daunorubicin is a chemotherapy medication used to treat cancer, specifically for AML. In this study, recombinant S. cerevisiae that could keep the small size of lysosomal vacuoles was constructed. Appropriate time and concentration to encapsulate the drug were then identified. In addition, release profile and anticancer effect of the drug in lysosome carriers were confirmed. According to this study, a more accurate encapsulation condition into lysosome can be optimized and potential application of S. cerevisiae derived lysosomes as drug carriers is confirmed.

Bioengineered bacterial vesicles as biological nano-heaters for optoacoustic imaging

Advances in genetic engineering have enabled the use of bacterial outer membrane vesicles (OMVs) to deliver vaccines, drugs and immunotherapy agents, as a strategy to circumvent biocompatibility and large-scale production issues associated with synthetic nanomaterials. We investigate bioengineered OMVs for contrast enhancement in optoacoustic (photoacoustic) imaging. We produce OMVs encapsulating biopolymer-melanin (OMVMel) using a bacterial strain expressing a tyrosinase transgene. Our results show that upon near-infrared light irradiation, OMVMel generates strong optoacoustic signals appropriate for imaging applications. In addition, we show that OMVMel builds up intense heat from the absorbed laser energy and mediates photothermal effects both in vitro and in vivo. Using multispectral optoacoustic tomography, we noninvasively monitor the spatio-temporal, tumour-associated OMVMel distribution in vivo. This work points to the use of bioengineered vesicles as potent alternatives to synthetic particles more commonly employed for optoacoustic imaging, with the potential to enable both image enhancement and photothermal applications.

Engineering a yeast double-molecule carrier for drug screening

With the advantages of unicellular eukaryotic structure and easy manipulation, yeast becomes a popular tool for biochemical, genetic and medicinal studies. In order to construct an efficient anti-inflammatory drug screening platform, we engineered yeast as a double-molecule carrier, of which an inserted domain (I domain) of lymphocyte function-associated antigen 1 was displayed on yeast surface and a green fluorescent protein (GFP) was expressed inside cytosol. The I domain specifically targeted a surface marker of mammalian cells, intercellular adhesion molecule 1, whose number is correlated with the level of cellular inflammation. Examination of GFP intensity enables swift quantification of the yeast-mammalian cell binding and thus it reflects inflammatory potency, herein the inflammatory index, of a chemical imposed to cells. The inflammatory potency of a total of 1340 chemicals was indexed. Among them, 1 inflammation-inducing and 1 inflammation-reducing compounds were verified both in vitro and in vivo. Our method demonstrated a swift, facile and high-throughput screening platform at the protein level for inflammation and related diseases drug discovery without using sophisticated instruments.

Affibody Molecules in Biotechnological and Medical Applications

Affibody molecules are small (6.5-kDa) affinity proteins based on a three-helix bundle domain framework. Since their introduction 20 years ago as an alternative to antibodies for biotechnological applications, the first therapeutic affibody molecules have now entered clinical development and more than 400 studies have been published in which affibody molecules have been developed and used in a variety of contexts. In this review, we focus primarily on efforts over the past 5 years to explore the potential of affibody molecules for medical applications in oncology, neurodegenerative, and inflammation disorders, including molecular imaging, receptor signal blocking, and delivery of toxic payloads. In addition, we describe recent examples of biotechnological applications, in which affibody molecules have been exploited as modular affinity fusion partners.

Self-assembled nanoparticles comprising aptide-SN38 conjugates for use in targeted cancer therapy

Self-assembled nanoparticles (NPs) have been intensively utilized as cancer drug delivery carriers because hydrophobic anticancer drugs may be efficiently loaded into the particle cores. In this study, we synthesized and evaluated the therapeutic index of self-assembled NPs chemically conjugated to a fibronectin extra domain B-specific peptide (APT_EDB) and an anticancer agent SN38. The APT_EDB-SN38 formed self-assembled structures with a diameter of 58 ± 3 nm in an aqueous solution and displayed excellent drug loading, solubility, and stability properties. A pharmacokinetic study revealed that the blood circulation half-life of SN38 following injection of the APT_EDB-SN38 NPs was markedly higher than that of the small molecule CPT-11. The APT_EDB-SN38 NPs delivered SN38 to tumor sites by both passive and active targeting. Finally, the APT_EDB-SN38 NPs exhibited potent antitumor activities and low toxicities against EDB-expressing tumors (LLC, U87MG) in mice. This system merits further preclinical and clinical investigations for SN38 delivery.

HER2-positive breast cancer targeting and treatment by a peptide-conjugated mini nanodrug

HER2+ breast cancer is one of the most aggressive forms of breast cancer. The new polymalic acid-based mini nanodrug copolymers are synthesized and specifically characterized to inhibit growth of HER2+ breast cancer. These mini nanodrugs are highly effective and in the clinic may substitute for trastuzumab (the marketed therapeutic antibody) and antibody-targeted nanobioconjugates. Novel mini nanodrugs are designed to have slender shape and small size. HER2+ cells were recognized by the polymer-attached trastuzumab-mimetic 12-mer peptide. Synthesis of the nascent cell-transmembrane HER2/neu receptors by HER2+ cells was inhibited by antisense oligonucleotides that prevented cancer cell proliferation and significantly reduced tumor size by more than 15 times vs. untreated control or PBS-treated group. We emphasize that the shape and size of mini nanodrugs can enhance penetration of multiple bio-barriers to facilitate highly effective treatment. Replacement of trastuzumab by the mimetic peptide favors reduced production costs and technical efforts, and a negligible immune response.