Mussel-Derived, Cancer-Targeting Peptide as pH-Sensitive Prodrug Nanocarrier

Multi-Stimuli-Responsive Nanoparticles Formed of POSS-PEG for the Delivery of Boronic Acid-Containing Therapeutics

Polymeric vehicles often exhibit batch-to-batch variations due to polydispersity, limiting their reproducibility for biomedical applications. In contrast, polyhedral oligomeric silsesquioxane (POSS) has emerged as an attractive candidate for drug delivery due to its precise chemical structure and rigid molecular shape. A promising strategy to enhance drug efficacy while reducing systemic toxicity is the development of multi-stimuli-responsive delivery systems capable of targeted drug release at a disease site. Herein, we developed a drug delivery platform based on POSS-polymer conjugates. By functionalizing the POSS with amino groups and establishing B-N coordination with boronic acids, the nanoparticles (NPs) exhibit responsive behavior to stimuli, including adenosine-5'-triphosphate (ATP), acidic pH, and nucleophilic reagents. We successfully encapsulated two boronic acid-containing molecules: tetraphenylethylene (TPE), serving as a fluorescent probe, and bortezomib (BTZ), an anticancer drug. The TPE@NPs were employed to visualize the cellular uptake of NPs by tumor cells, while the BTZ@NPs exhibited increased cytotoxicity in tumor cells compared with normal cells. This POSS-PEG conjugate offers a nanoparticle platform for encapsulating versatile boronic acid-containing molecules, thereby enhancing drug efficacy while minimizing systemic toxicity. Given the wide-ranging applications of boronic acid-containing molecules in biomedicine, our platform holds significant promise for the development of intelligent drug delivery systems for diagnostics and therapeutics.

Sialic Acid Engineered Prodrug Nanoparticles for Codelivery of Bortezomib and Selenium in Tumor Bearing Mice

Most cancer patients rarely benefit from monodrug therapy because of both cancer complexity and tumor environment. One of the main reasons for this failure is insufficient accumulation of the optimal dose at the tumorous site. Our investigation implies a promising strategy to engineer prodrug nanoparticles (NPs) of bortezomib (BTZ) and selenium (Se) using sialic acid (SAL) as a ligand to improve breast cancer therapy. BTZ was conjugated with SAL and HPMA (N-2-hydroxypropyl methacrylamide) to prepare a prodrug conjugate; BTZ-SAL-HPMA (BSAL-HP) and then fabricated into prodrug NPs with Se (Se_BSAL-HP prodrug NPs). The self-assembly of prodrug NPs functionalized with Se showed size (204.13 ± 0.02 nm) and zeta potential (-31.0 ± 0.11 mV) in dynamic light scattering (DLS) experiments and spherical shape in TEM and SEM analysis. Good stability and low pH drug release profile were characterized by Se_BSAL-HP prodrug NPs. The tumor-selective boronate-ester-based prodrug NPs of BTZ in combination with Se endowed a synergistic effect against cancer cells. Compared to prodrug conjugate, Se_BSAL-HP prodrug NPs exhibited higher cell cytotoxicity and enhanced cellular internalization with significant changes in mitochondria membrane potential (MMP). Elevated apoptosis was observed in the (G2/M) phase of the cell cycle for Se_BSAL-HP prodrug NPs (2.7-fold) higher than BTZ. In vivo studies were performed on Sprague-Dawley rats and resulted in positive trends. The increased therapeutic activity of Se_BSAL-HP prodrug NPs inhibited primary tumor growth and showed 43.05 fold decrease in tumor volume than the control in 4T1 tumor bearing mice. The surprising and remarkable outcomes for Se_BSAL-HP prodrug NPs were probably due to the ROS triggering effect of boronate ester and selenium given together.

Construction of multi-program responsive vitamin E succinate-chitosan-histidine nanocarrier and its response strategy in tumor therapy

Multifunctional drug delivery carriers have emerged as a promising cancer drug delivery strategy. Here, we developed a vitamin E succinate-chitosan-histidine (VCH) multi-program responsive drug carrier. The structure was characterized by FT-IR and 1H NMR spectrum, and the DLS and SEM results showed typical nanostructures. The drug loading content was 21.0 % and the corresponding encapsulation efficiency was 66.6 %. The UV-vis and fluorescence spectra demonstrated the existence of the π-π stacking interaction between DOX and VCH. Drug release experiments implied good pH sensitivity and sustained-release effect. The DOX/VCH nanoparticles could be efficiently taken up by HepG2 cancer cells and the tumor inhibition rate was up to 56.27 %. The DOX/VCH reduced the tumor volume and weight efficiently with a TIR of 45.81 %. The histological analysis results showed that DOX/VCH could effectively inhibit tumor growth and proliferation, and there was no damage to normal organs. VCH nanocarriers could combine the advantages of VES, histidine and chitosan to achieve pH sensitivity and P-gp inhibition, and effectively improve the drug solubility, targeting and lysosomal escape. Through the program response of different micro-environment, the newly developed polymeric micelles could successfully be utilized as a multi-program responsive nanocarrier system for the treatment of cancers.

Organic Nanodelivery Systems as a New Platform in the Management of Breast Cancer: A Comprehensive Review from Preclinical to Clinical Studies

Breast cancer accounts for approximately 25% of cancer cases and 16.5% of cancer deaths in women, and the World Health Organization predicts that the number of new cases will increase by almost 70% over the next two decades, mainly due to an ageing population. Effective diagnostic and treatment strategies are, therefore, urgently required for improving cure rates among patients since current therapeutic modalities have many limitations and side effects. Nanomedicine is evolving as a promising approach for cancer management, including breast cancer, and various types of organic and inorganic nanomaterials have been investigated for their role in breast cancer diagnosis and treatment. Following an overview on breast cancer characteristics and pathogenesis and challenges of the current treatment strategies, the therapeutic potential of biocompatible organic-based nanoparticles such as liposomes and polymeric micelles that have been tested in breast cancer models are reviewed. The efficacies of different drug delivery and targeting strategies are documented, ranging from synthetic to cell-derived nanoformulations together with a summary of the interaction of nanoparticles with externally applied energy such as radiotherapy. The clinical translation of nanoformulations for breast cancer treatment is summarized including those undergoing clinical trials.

Amyloid-like aggregates of short self-assembly peptide selectively induce melanoma cell apoptosis

With the rising global incidence of melanoma, new anti-melanoma drugs with low-inducing drug resistance and high selectivity are in urgent need. Inspired by the physiological events in which fibrillar aggregates formed by amyloid proteins are toxic to normal tissues, we here rationally design a tyrosinase responsive peptide, I₄K₂Y* (Ac-IIIIKKDopa-NH₂). Such peptide self-assembled into long nanofibers outside the cells, while it was catalyzed into amyloid-like aggregates by tyrosinase which was rich in melanoma cells. The newly formed aggregates concentrated around the nucleus of melanoma cells, blocking the exchange of biomolecules between the nucleus and cytoplasm and finally leading to cell apoptosis via the S phase arrest in cell cycle distribution and dysfunction of mitochondria. Furthermore, I₄K₂Y* effectively inhibited B16 melanoma growth in a mouse model but with minimal side effects. We believe that the strategy of combining the usage of toxic amyloid-like aggregates and in-situ enzymatic reactions by specific enzymes in tumor cells will bring profound implications for designing new anti-tumor drugs with high selectivity.

N-2-Hydroxypropylmethacrylamide-Polycaprolactone Polymeric Micelles in Co-delivery of Proteasome Inhibitor and Polyphenol: Exploration of Synergism or Antagonism

Breast cancer leads to the highest mortality among women resulting in a major clinical burden. Multidrug therapy is more efficient in such patients compared to monodrug therapy. Simultaneous combinatorial or co-delivery garnered significant interest in the past years. Caffeic acid (CFA) (a natural polyphenol) has received growing attention because of its anticarcinogenic and antioxidant potential. Bortezomib (BTZ) is a proteasome inhibitor and may be explored for treating breast cancer. Despite its high anticancer activity, the low water solubility and chemical instability restrict its efficacy against solid tumors. In the present study, we designed and investigated a HP-PCL (N-2-hydroxypropylmethacrylamide-polycaprolactone) polymeric micellar (PMCs) system for the simultaneous delivery of BTZ and CFA in the treatment of breast cancer. The designed BTZ+CFA-HP-PCL PMCs were fabricated, optimized, and characterized for size, zeta potential, surface morphology, and in vitro drug release. Developed nanosized (174.6 ± 0.24 nm) PMCs showed enhanced cellular internalization and cell cytotoxicity in both MCF-7 and MDA-MB-231 cells. ROS (reactive oxygen species) levels were highest in BTZ-HP-PCL PMCs, while CFA-HP-PCL PMCs significantly (p < 0.001) scavenged the ROS generated in 2',7'-dichlorofluorescein diacetate (DCFH-DA) assay. The mitochondrial membrane potential (MMP) assay revealed intense and significant green fluorescence in both types of cancer cells when treated with BTZ-HP-PCL PMCs (p < 0.001) indicating apoptosis or cell death. The pharmacokinetic studies revealed that BTZ-HP-PCL PMCs and BTZ+CFA-HP-PCL PMCs exhibited the highest bioavailability, enhanced plasma half-life, decreased volume of distribution, and lower clearance rate than the pure combination of drugs. In the organ biodistribution studies, the combination of BTZ+CFA showed higher distribution in the spleen and the heart. Overall findings of in vitro studies surprisingly resulted in better therapeutic efficiency of BTZ-HP-PCL PMCs than BTZ+CFA-HP-PCL PMCs. However, the in vivo tumor growth inhibition study performed in tumor-induced mice concluded that the tumor growth was inhibited by both BTZ-HP-PCL PMCs and BTZ+CFA-HP-PCL PMCs (p < 0.0001) more efficiently than pure BTZ and the combination (BTZ+CFA), which may be due to the conversion of boronate ester into boronic acid. Henceforth, the combination of BTZ and CFA provides further indications to be explored in the future to support the hypothesis that BTZ may work with polyphenol (CFA) in the acidic environment of the tumor.

Size Regulation of Polydopamine Nanoparticles by Boronic Acid and Lewis Base

Size regulation of polydopamine nanoparticles (PDA NPs) is vital to melanin-inspired materials. The general strategy usually focuses on tuning of the reaction parameters which could affect the dopamine (DA) monomer polymerization process, such as pH, temperature, monomer concentration, etc. The reaction between boronic acids and catechols to form boronic esters has been widely applied in many fields, but little attention has been paid in the size regulation of PDA NPs. Here, it is speculated that the fine size regulation of PDA NPs can be directly achieved by using boronic acids and Lewis base molecules. It is found that these issues could indeed significantly affect the stability of the boronic esters formed by boronic acids and DA, which may further inhibit the monomer polymerization kinetics and tune the particle size of the resulting PDA NPs. It is also found that the several intrinsic properties of PDA NPs such as the free radical scavenging ability, UV spectral absorption, photothermal behavior, and structural color all change with the particle size. It is believed that this work can provide new opportunities for fabricating melanin-inspired PDA NPs with well controlled size and properties.

Lysosomal-mediated drug release and activation for cancer therapy and immunotherapy

The development of carrier systems that are able to transport and release therapeutics to target cells is an emergent strategy to treat cancer; however, they following endocytosis are usually trapped in the endo/lysosomal compartments. The efficacy of drug conjugates and nanotherapeutics relies critically on their intracellular drug release ability, for which advanced systems responding to the unique lysosomal environment such as acidic pH and abundant enzymes (e.g. cathepsin B, sulfatase and β-glucuronidase) or equipped with photochemical internalization property have been energetically pursued. In this review, we highlight the recent designs of smart systems that promote efficient lysosomal release and/or escape of anticancer agents including chemotherapeutics (e.g. doxorubicin, platinum, chloroquine and hydrochloroquine) and biotherapeutics (e.g. proteins, siRNA, miRNA, mRNA and pDNA) to cancer cells or immunotherapeutic agents (e.g. antigens, mRNA and immunoadjuvants) to antigen-presenting cells (APCs), thereby boosting cancer therapy and immunotherapy. Lysosomal-mediated drug release presents an appealing approach to develop innovative cancer therapeutics and immunotherapeutics.

Tailoring carrier-free nanocombo of small-molecule prodrug for combinational cancer therapy

The outcomes of monotherapy could not satisfy clinical cancer treatment owing to the challenges of tumor heterogeneity, multi-drug resistance, tumor metastasis and relapse. In response, the significance of combinational cancer therapy has been highlighted. Traditional combinational schemes usually utilize "free" drug for multi drug administration, independently. The diverse pharmacokinetics and biodistribution greatly hinder the antitumor effects and cause systematic toxicity. To tackle the hinderance, various nanoparticulate drug delivery systems (Nano-DDSs) have been developed. However, conventional Nano-DDSs encapsulate drugs into carrier materials through noncovalent interactions, resulting in low drug loading, fixed multi drug encapsulation ratio, chemical instability and carrier-associated toxicity. Recently, carrier-free nanocombos based on self-assembling small-molecule prodrugs (SPNCs) have emerged as a versatile Nano-DDSs for multiple drug delivery. Benefited by the self-assembly capability, SPNCs could be facilely fabricated with distinct merits of ultra-high drug loading, adjustable drug ratio and negligible carrier-associated toxicity. Herein, we summarize the latest trends of SPNCs. First, a basic review on self-assembling small-molecule prodrugs is presented. Additionally, facile techniques to prepare SPNCs are introduced. Furthermore, advanced combinational therapies based on SPNCs are spotlighted with special emphasis on synergistic mechanisms. Finally, future prospects and challenges are discussed.

Allyl phenyl selenides as H2O2 acceptors to develop ROS-responsive theranostic prodrugs

Reactive oxygen species (ROS)-responsive prodrugs have received significant attention due to their capacity to target tumors to relieve the side effects caused by chemotherapy. Herein, a series of novel H₂O₂-activated theranostic prodrugs (CPTSe1-CPTSe7) were developed containing allyl phenyl selenide moieties as H₂O₂ acceptors. Compared with conventional boronate ester-based prodrug CPT-B, CPTSe1 was more stable in human plasma and showed a more complete release of camptothecin (CPT) in H₂O₂ inducing experiment. The selectively activated fluorescence signals of CPTSe1 in tumor cells make it useful for real-time monitoring of CPT release and H₂O₂ detection. Furthermore, excellent selectivity of CPTSe1 was achieved for tumor cells over normal cells. Our results provide a new platform for the development of H₂O₂-responsive theranostic prodrugs.

Mussel-Inspired Clickable Antibacterial Peptide Coating on Ureteral Stents for Encrustation Prevention

Long-term indwelling catheters or stents often cause complications like infection, encrustation, hematuria, pain, and so on. The source of these problems is bacteria, which can form biofilms on the stents to reduce antibiotic sensitivity and produce urease to form encrustation by increasing the urine pH. Urinary tract infection (UTI) can aggravate the body damage and even seriously endanger lives, and the encrustation will block the stents, which can cause hydronephrosis and renal function damage. Therefore, the prevention of UTI and encrustation represents a great challenge in clinical ureteral stent uses. In this work, a clickable mussel-inspired peptide and antimicrobial peptide (AMP) were used to functionalize the commercial stents' surfaces to inhibit long-term infection and encrustation caused by bacteria. Copper (Cu) ions were used to coordinate the mussel-inspired peptide to improve the stability. The AMP with an azido group was clicked to the mussel-inspired Cu-coordinated peptide coating through click chemistry. The bio-inspired antibacterial coating was constructed with excellent stability, bactericidal properties, and improved biological compatibility. In in vitro and in vivo experiments, it was further found that the coating showed bactericidal and encrustation reduction abilities. This study thus developed an effective, safe, and stable AMP coating on urinary stents/catheters capable of long-term antibacterial and encrustation inhibition.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

Stimulus-responsive self-assembled prodrugs in cancer therapy

Small-molecule prodrugs have become the main toolbox to improve the unfavorable physicochemical properties of potential therapeutic compounds in contemporary anti-cancer drug development. Many approved small-molecule prodrugs, however, still face key challenges in their pharmacokinetic (PK) and pharmacodynamic (PD) properties, thus severely restricting their further clinical applications. Self-assembled prodrugs thus emerged as they could take advantage of key benefits in both prodrug design and nanomedicine, so as to maximize drug loading, reduce premature leakage, and improve PK/PD parameters and targeting ability. Notably, temporally and spatially controlled release of drugs at cancerous sites could be achieved by encoding various activable linkers that are sensitive to chemical or biological stimuli in the tumor microenvironment (TME). In this review, we have comprehensively summarized the recent progress made in the development of single/multiple-stimulus-responsive self-assembled prodrugs for mono- and combinatorial therapy. A special focus was placed on various prodrug conjugation strategies (polymer-drug conjugates, drug-drug conjugates, etc.) that facilitated the engineering of self-assembled prodrugs, and various linker chemistries that enabled selective controlled release of active drugs at tumor sites. Furthermore, some polymeric nano-prodrugs that entered clinical trials have also been elaborated here. Finally, we have discussed the bottlenecks in the field of prodrug nanoassembly and offered potential solutions to overcome them. We believe that this review will provide a comprehensive reference for the rational design of effective prodrug nanoassemblies that have clinic translation potential.

Carrier-Free Nanomedicine for Cancer Immunotherapy

With the rapid development of nanotechnology, carrier-based nano-drug delivery systems (DDSs) have been widely studied due to their advantages in optimizing pharmacokinetic and distribution profiles. However, despite those merits, some carrier-related limitations, such as low drug-loading capacity, systematic toxicity and unclear metabolism, usually prevent their further clinical transformation. Carrier-free nanomedicines with non-therapeutic excipients, are considered as an excellent paradigm to overcome these obstacles, owing to their superiority in improving both drug delivery efficacy and safety concern. In recent years, carrier-free nanomedicines have opened new horizons for cancer immunotherapy, and have already made outstanding progress. Herein, in this review, we are focusing on making an integrated and exhaustive overview of lately reports about them. Firstly, the major synthetic strategies of carrier-free nanomedicines are introduced, such as nanocrystals, prodrug-, amphiphilic drug-drug conjugates (ADDCs)-, polymer-drug conjugates-, and peptide-drug conjugates (PepDCs)-assembled nanomedicines. Afterwards, the typical applications of carrier-free nanomedicines in cancer immunotherapy are well-discussed, including cancer vaccines, cytokine therapy, enhancing T-cell checkpoint inhibition, as well as modulating tumor microenvironment (TME). After that, both the advantages and the potential challenges, as well as the future prospects of carrier-free nanomedicines in cancer immunotherapy, were discussed. And we believe that it would be of great potential practiced and reference value to the relative fields.

Nanomedicine-enabled chemotherapy-based synergetic cancer treatments

Chemotherapy remains one of the most prevailing regimens hitherto in the fight against cancer, but its development has been being suffering from various fatal side effects associated with the non-specific toxicity of common chemical drugs. Advances in biomedical application of nanomedicine have been providing alternative but promising approaches for cancer therapy, by leveraging its excellent intrinsic physicochemical properties to address these critical concerns. In particular, nanomedicine-enabled chemotherapy has been established as a safer and promising therapeutic modality, especially the recently proposed nanocatalytic medicine featuring the capabilities to generate toxic substances by initiating diverse catalytic reactions within the tumor without directly relying on highly toxic but non-selective chemotherapeutic agents. Of special note, under exogenous/endogenous stimulations, nanomedicine can serve as a versatile platform that allows additional therapeutic modalities (photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), etc.) to be seamlessly integrated with chemotherapy for efficacious synergistic treatments of tumors. Here, we comprehensively review and summarize the representative studies of multimodal synergistic cancer treatments derived from nanomedicine and nanocatalytic medicine-enabled chemotherapy in recent years, and their underlying mechanisms are also presented in detail. A number of existing challenges and further perspectives for nanomedicine-synergized chemotherapy for malignant solid tumor treatments are also highlighted for understanding this booming research area as comprehensively as possible.

Emerging Theranostic Nanomaterials in Diabetes and Its Complications

Diabetes mellitus (DM) refers to a group of metabolic disorders that are characterized by hyperglycemia. Oral subcutaneously administered antidiabetic drugs such as insulin, glipalamide, and metformin can temporarily balance blood sugar levels, however, long-term administration of these therapies is associated with undesirable side effects on the kidney and liver. In addition, due to overproduction of reactive oxygen species and hyperglycemia-induced macrovascular system damage, diabetics have an increased risk of complications. Fortunately, recent advances in nanomaterials have provided new opportunities for diabetes therapy and diagnosis. This review provides a panoramic overview of the current nanomaterials for the detection of diabetic biomarkers and diabetes treatment. Apart from diabetic sensing mechanisms and antidiabetic activities, the applications of these bioengineered nanoparticles for preventing several diabetic complications are elucidated. This review provides an overall perspective in this field, including current challenges and future trends, which may be helpful in informing the development of novel nanomaterials with new functions and properties for diabetes diagnosis and therapy.

Assembly of catechol-modified polymer brushes for drug delivery

The anticancer drug of Bortezomib conjugated onto catechol-modified bottlebrush block copolymers can be intracellularly released owing to the pH-responsive behavior, resulting in considerable cell death and tumor growth inhibition.

Intracellular Enzyme-Responsive Profluorophore and Prodrug Nanoparticles for Tumor-Specific Imaging and Precise Chemotherapy

Responsive drug delivery systems possess great potential in disease diagnosis and treatment. Herein, we develop an activatable prodrug and fluorescence imaging material by engineering the endogenous NAD(P)H:quinone oxidoreductase-1 (NQO1) responsive linker. The as-prepared nanomaterials possess the NQO1-switched drug release and fluorescence enablement, which realizes the tumor-specific chemotherapy and imaging in living mice. The enzyme-sensitive prodrug nanoparticles exhibit selectively potent anticancer performance to NQO1-positive cancer and ignorable off-target toxicity. This work provides an alternative strategy for constructing smart prodrug nanoplatforms with precision, selectivity, and practicability for advanced cancer imaging and therapy.

Bioclickable Mussel-Derived Peptides With Immunoregulation for Osseointegration of PEEK

Polyether ether ketone (PEEK)–based biomaterials have been widely used in the field of spine and joint surgery. However, lack of biological activity limits their further clinical application. In this study, we synthesized a bioclickable mussel-derived peptide Azide-DOPA₄ as a PEEK surface coating modifier and further combined bone morphogenetic protein 2 functional peptides (BMP2p) with a dibenzylcyclooctyne (DBCO) motif through bio-orthogonal reactions to obtain DOPA₄@BMP2p-PEEK. As expected, more BMP2p can be conjugated on PEEK after Azide-DOPA₄ coating. The surface roughness and hydrophilicity of DOPA₄@BMP2p-PEEK were obviously increased. Then, we optimized the osteogenic capacity of PEEK substrates. In vitro, compared with the BMP2p-coating PEEK material, DOPA₄@BMP2p-PEEK showed significantly higher osteogenic induction capability of rat bone marrow mesenchymal stem cells. In vivo, we constructed a rat calvarial bone defect model and implanted PEEK materials with a differently modified surface. Micro-computed tomography scanning displayed that the DOPA₄@BMP2p-PEEK implant group had significantly higher new bone volume and bone mineral density than the BMP2p-PEEK group. Histological staining of hard tissue further confirmed that the DOPA₄@BMP2p-PEEK group revealed a better osseointegrative effect than the BMP2p-PEEK group. More importantly, we also found that DOPA₄@BMP2p coating has a synergistic effect with induced Foxp3+ regulatory T (iTreg) cells to promote osteogenesis. In summary, with an easy-to-perform, two-step surface bioengineering approach, the DOPA₄@BMP2p-PEEK material reported here displayed excellent biocompatibility and osteogenic functions. It will, moreover, offer insights to engineering surfaces of orthopedic implants.

Nanoparticulation of Prodrug into Medicines for Cancer Therapy

This article provides a broad spectrum about the nanoprodrug fabrication advances co-driven by prodrug and nanotechnology development to potentiate cancer treatment. The nanoprodrug inherits the features of both prodrug concept and nanomedicine know-how, attempts to solve underexploited challenge in cancer treatment cooperatively. Prodrugs can release bioactive drugs on-demand at specific sites to reduce systemic toxicity, this is done by using the special properties of the tumor microenvironment, such as pH value, glutathione concentration, and specific overexpressed enzymes; or by using exogenous stimulation, such as light, heat, and ultrasound. The nanotechnology, manipulating the matter within nanoscale, has high relevance to certain biological conditions, and has been widely utilized in cancer therapy. Together, the marriage of prodrug strategy which shield the side effects of parent drug and nanotechnology with pinpoint delivery capability has conceived highly camouflaged Trojan horse to maneuver cancerous threats.

Cancer Cell Preferential Penetration and pH-Responsive Drug Delivery of Oligorutin

We report herein a novel delivery system, derived from the facile enzymatic synthesis of oligorutin (OR), for cancer cell targeting and pH-responsive drug delivery. In this study, we demonstrate that OR could preferentially penetrate cancer cells via the lipid raft-mediated endocytosis pathway, and cell membrane cholesterol was critical to the internalization of OR. The accumulation of OR in the tumor region was further confirmed by an in vivo biodistribution study. Considering the tumor-targeting property of OR, a pH-responsive drug delivery system (OR-BTZ) was developed by covalent conjugation of the catechol groups on OR with antitumor drug bortezomib (BTZ) through a pH-sensitive borate ester bond. OR-BTZ exerted cytotoxicity as well as inhibition of the migration and invasion to hepatoma carcinoma cells and showed no apparent cytotoxicity with liver normal cells. The OR-BTZs also presented significant therapeutic efficacy and low systematic toxicity in the murine hepatocellular carcinoma model. To our knowledge, this study presents the first attempt to exploit the potential of oligoflavonoids for cancer cell-targeted drug delivery and will motivate the development of flavonoids and their derivatives as a new type of biomaterials for tumor-targeted therapy.

"Plug and Play" Functionalized Erythrocyte Nanoplatform for Target Atherosclerosis Management

For atherosclerosis (AS) management, a therapeutic drug intervention is the most widely used strategy. However, there are some problems such as low location specificity, high intake, and side effects. Nanomedicine can prolong the half-life of drug solubilization, reduce toxic and side effects, and improve the distribution of drug objects. Herein, to overcome the challenges, an erythrocyte-based "plug and play" nanoplatform was developed by incorporating the vascular cell adhesion molecule-1 (VCAM-1) targeting and the acid stimulus responsibility. After the function moieties conjugated with DSPE-PEG, the targeting peptide and the acid-sensitive prodrug were conveniently integrated into red blood cells' surface for enhancing target AS drug delivery and controlling local drug release. As a proof of principle, a plug and play nanoplatform with targeted drug delivery and acid-control drug release is demonstrated, achieving a marked therapeutic effect for AS.

Novel Molecular Organic Framework Composite Molecularly Imprinted Nanofibrous Membranes with a Bioinspired Viscid Bead Structure for Selective Recognition and Separation of Atrazine

In this work, novel atrazine (ATZ) molecularly imprinted nanofibrous membranes (A-MNMs) with a molecular organic framework (MOF)-based viscid bead structure were developed based on a natural spider-web-inspired strategy for selective separation of ATZ. Poly(vinylidene fluoride)/poly(vinyl alcohol) (PVDF/PVA) blended nanofibrous membranes as the basal membrane were synthesized by electrospinning technology combined with a chemical cross-linking procedure. The most critical design is that MOF nanocrystals as the matrix of the viscid bead structure were assembled on the PVDF/PVA blended nanofibrous membrane surface and the specific recognition sites were efficiently constructed on the surface and pores of the MOF-based viscid bead structure by a surface imprinting strategy. Significantly, the as-synthesized MOF-based viscid bead structure has an enhanced specific surface area, which helps to form abundant specific recognition sites in A-MNMs. Therefore, the A-MNMs with a spider-web-like structure presented an enhanced rebinding capacity (37.62 mg g^-1) and permselectivity (permselectivity factors β were 4.21 and 4.31) toward ATZ. Moreover, the A-MNMs display strong practicability in separation of ATZ from simulated environmental water samples. The presented work has shown tremendous potential for preparing natural spider-web-like molecularly imprinted membranes (MIMs) for selective separation of environment pollutants.

Recent advances in prodrug-based nanoparticle therapeutics

Extensive research into prodrug modification of active pharmaceutical ingredients and nanoparticle drug delivery systems has led to unprecedented levels of control over the pharmacological properties of drugs and resulted in the approval of many prodrug or nanoparticle-based therapies. In recent years, the combination of these two strategies into prodrug-based nanoparticle drug delivery systems (PNDDS) has been explored as a way to further advance nanomedicine and identify novel therapies for difficult-to-treat indications. Many of the PNDDS currently in the clinical development pipeline are expected to enter the market in the coming years, making the rapidly evolving field of PNDDS highly relevant to pharmaceutical scientists. This review paper is intended to introduce PNDDS to the novice reader while also updating those working in the field with a comprehensive summary of recent efforts. To that end, first, an overview of FDA-approved prodrugs is provided to familiarize the reader with their advantages over traditional small molecule drugs and to describe the chemistries that can be used to create them. Because this article is part of a themed issue on nanoparticles, only a brief introduction to nanoparticle-based drug delivery systems is provided summarizing their successful application and unfulfilled opportunities. Finally, the review's centerpiece is a detailed discussion of rationally designed PNDDS formulations in development that successfully leverage the strengths of prodrug and nanoparticle approaches to yield highly effective therapeutic options for the treatment of many diseases.

pH-triggered solubility and cytotoxicity changes of malachite green derivatives incorporated in liposomes for killing cancer cells

Three different malachite green leuco derivatives (MG-Xs) are incorporated in liposomes. In all three cases, a substituent (X) is covalently linked to the central carbon atom, abbreviated as MG-OH, MG-OCH3, and MG-CN. The three MG-X compounds are solubilized separately in liposome membranes and become cationic (MG+) and water soluble under acidic conditions. MG+ is consequently released from the liposome to the aqueous exterior. Their release behavior corresponds to their ionization ability: MG-OH > MG-OCH3 > MG-CN. The cellular uptake of the liposomes, the cytotoxic effect, and the location of MG+ in cancer cells are investigated using murine cells derived from colon cancer (Colon 26 cells) and human embryonic kidney cells (HEK 293 cells). The toxic effect on cancer cells is correlated to the ionization ability of MG-Xs. The liposomes effectively deliver MG+via the endocytic pathway, resulting in the cytotoxicity of liposomes containing MG-OH which is higher than that of free MG-OH and MG+. The difference in the phospholipids constituting the liposome membranes barely had an effect on the ionization ratio and the cytotoxicity of MG-OH. Confocal fluorescence microscopic observations revealed that MG+ is ultimately transported into the nuclei after being released in acidic cellular compartments.

A Novel Acid-Degradable PEG Crosslinker for the Fabrication of pH-Responsive Soft Materials

The design and synthesis of a novel acid-degradable polyethylene glycol-based N-hydroxysuccinimide (NHS) ester-activated crosslinker is reported. The crosslinker is reactive towards nucleophiles and features a central ketal functional group that is stable at pH > 7.5 and rapidly hydrolyses at pH > 6.0. The crosslinker is used to (i) fabricate acid-degradable polysaccharide hydrogels that exhibit controlled degradation upon exposure to an acidic environment or via endogenous enzyme activity; and (ii) construct hydrogel-filled protein-polymer microcompartments (termed proteinosomes) capable of pH-dependent membrane disassembly. Taken together the results provide new opportunities for the fabrication of pH-responsive soft materials with potential applications in drug delivery, tissue engineering, and soft-matter bioengineering.

Surface bioengineering of diverse orthopaedic implants with optional functions via bioinspired molecular adhesion and bioorthogonal conjugations

In this work, we reported an upgraded mussel-inspired strategy for surface bioengineering of osteoimplants by combination of mussel adhesion and bioorthogonal click chemistry. The main idea of this strategy is a mussel-inspired synthetic peptide containing multiple 3,4-dihydroxy-L-phenylalanine (DOPA) units and a dibenzocyclooctyne (DBCO) terminal (DOPA-DBCO). According to the mussel adhesion mechanism, the DOPA-DBCO peptide could stably adhere onto a variety of material surface, leaving the residual DBCO groups on the surface. Then, the DBCO residues could be employed for a second-step bioorthogonal conjugation with azide-capping biomolecules through bioorthogonal click chemistry, finally leading to the biomodified surfaces. To demonstrate the generality of our strategy for surface biomodification of diversified orthopaedic materials including metallic and polymeric substrates, we here conceptually conjugated some typical azide-capping biomolecules on both metal and polymeric surfaces. The results definitely verified the feasibility for engineering of functional surfaces with some essential requirements of osteoimplants, for example, the ability to facilitate cell adhesion, suppress bacterial infection, and promote osteogenesis. In a word, this study indicated that our novel surface strategy would show broad applicability for diverse osteoimplants and in different biological scenarios. We can also image that the molecular specificity of bioorthogonal conjugation and the universality of mussel adhesion mechanism may jointly provide a versatile surface bioengineering method for a wider range of biomedical implants.

Carrier-free nanodrugs for safe and effective cancer treatment

Clinical applications of many anti-cancer drugs are restricted due to their hydrophobic nature, requiring use of harmful organic solvents for administration, and poor selectivity and pharmacokinetics resulting in off-target toxicity and inefficient therapies. A wide variety of carrier-based nanoparticles have been developed to tackle these issues, but such strategies often fail to encapsulate drug efficiently and require significant amounts of inorganic and/or organic nanocarriers which may cause toxicity problems in the long term. Preparation of nano-formulations for the delivery of water insoluble drugs without using carriers is thus desired, requiring elegantly designed strategies for products with high quality, stability and performance. These strategies include simple self-assembly or involving chemical modifications via coupling drugs together or conjugating them with various functional molecules such as lipids, carbohydrates and photosensitizers. During nanodrugs synthesis, insertion of redox-responsive linkers and tumor targeting ligands endows them with additional characteristics like on-target delivery, and conjugation with immunotherapeutic reagents enhances immune response alongside therapeutic efficacy. This review aims to summarize the methods of making carrier-free nanodrugs from hydrophobic drug molecules, evaluating their performance, and discussing the advantages, challenges, and future development of these strategies.

Dimerization-induced self-assembly of a redox-responsive prodrug into nanoparticles for improved therapeutic index

Although some formats of nanomedicines are now available for clinical use, the translation of new nanoparticles to the clinic remains a considerable challenge. Here, we describe a simple yet cost-effective strategy that converts a toxic drug, cabazitaxel, into a safe and effective nanomedicine. The strategy involves the ligation of drug molecules via a self-immolating spacer, followed by dimerization-induced self-assembly to assemble stable nanoparticles. Self-assembled cabazitaxel dimers could be further refined by PEGylation with amphiphilic polymers suitable for preclinical studies. This protocol enables the formation of systemically injectable nanoparticles (termed SNPs) with nearly quantitative entrapment efficiencies and exceptionally high drug loading (> 86%). In healthy mice, PEGylated SNPs show a favorable safety profile, with reduced systemic toxicity and negligible immunotoxicity. In two separate mouse xenograft models of cancer, administration of SNPs produces efficient antitumor activity with durable tumor suppression during therapeutic studies. Overall, this methodology opens up a practical and expedient route for the fabrication of clinically useful nanomedicines, transforming a hydrophobic and highly toxic drug into a systemic self-deliverable nanotherapy. STATEMENT OF SIGNIFICANCE: Despite the great progress in cancer nanomedicines, clinical translation of nanomedicines still remains a considerable challenge. In this study, we designed a self-assembling nanoplatform based on cabazitaxel dimer reversibly ligated via a bioactivatable linker. This approach enabled the generation of systemically injectable nanomedicines with quantitative entrapment efficiencies and exceptionally high drug loading (> 86%), which greatly obviates concerns about excipient-associated side effects. Self-assembled dimeric cabazitaxel exhibited a higher safety profile than free cabazitaxel and negligible immunotoxicity in animals. This is a practical and expedient example how the chemical ligation of a hydrophobic and highly toxic anticancer drug can be leveraged to create a self-assembling delivery nanotherapy which preserves inherent pharmacologic efficacy while reduces in vivo systemic and immune toxicity.

Peptides, proteins and nanotechnology: a promising synergy for breast cancer targeting and treatment

INTRODUCTION

The use of nanoparticles for breast cancer targeting and treatment has become a reality. They are safe and possess interesting peculiarities such as the unspecific accumulation into the tumor site and the possibility to activate controlled drug release as compared to free drugs. However, there are still many areas of improvement which can certainly be addressed with the use of peptide-based elements.

AREAS COVERED

The article reviews different preclinical strategies employing peptides and proteins in combination with nanoparticles for breast cancer targeting and treatment as well as peptide and protein-targeted encapsulated drugs, and it lists the current clinical status of therapies using peptides and proteins for breast cancer.

EXPERT OPINION

The conjugation of protein and peptides can improve tumor homing of nanoparticles, increase cellular penetration and attack specific drivers and vulnerabilities of the breast cancer cell to promote tumor cytotoxicity while reducing secondary effects in healthy tissues. Examples are the use of antibodies, arginylglycylaspartic acid (RGD) peptides, membrane disruptive peptides, interference peptides, and peptide vaccines. Although their implementation in the clinic has been relatively slow up to now, we anticipate great progress in the field which will translate into more efficacious and selective nanotherapies for breast cancer.

PH and redox dual-responsive polymeric micelles with charge conversion for paclitaxel delivery

Here we demonstrate a type of pH and redox dual-responsive micelles, which were self-assembled in aqueous solution by an amphiphilic polymer, methoxypoly(ethylene glycol)-cystamine-poly(L-glutamic acid)-imidazole (mPEG-SS-PGA-IM). Considering tumor cells or tissues exhibiting low pH values and high glutathione (GSH) concentration, mPEG-SS-PGA-IM micelles possessed the charge conversion at pH of tumor tissues, which can facilitate cellular uptake of tumor cells. Furthermore, mPEG-SS-PGA-IM micelles can escape from endo/lysosomes based on the proton sponge effect, following degraded by higher concentration of GSH in cytoplasm. CLSM images of HCT116 cells indicated that mPEG-SS-PGA-IM micelles can escape from endo/lysosomes and enter cytoplasm. MTT assay showed that (paclitaxel) PTX-loaded mPEG-SS-PGA-IM micelles had higher cytotoxicity against HCT116 cells compared with PTX-loaded mPEG-PBLG and mPEG-SS-PBLG micelles. These results indicated that these mPEG-SS-PGA-IM micelles, as novel and effective pH- and redox-responsive nanocarriers, have great potential to both improve drug targeting efficiency while also enhancing the antitumor efficacy of PTX.

Bioclickable and mussel adhesive peptide mimics for engineering vascular stent surfaces

Thrombogenic reaction, aggressive smooth muscle cell (SMC) proliferation, and sluggish endothelial cell (EC) migration onto bioinert metal vascular stents make poststenting reendothelialization a dilemma. Here, we report an easy to perform, biomimetic surface engineering strategy for multiple functionalization of metal vascular stents. We first design and graft a clickable mussel-inspired peptide onto the stent surface via mussel-inspired adhesion. Then, two vasoactive moieties [i.e., the nitric-oxide (NO)-generating organoselenium (SeCA) and the endothelial progenitor cell (EPC)-targeting peptide (TPS)] are clicked onto the grafted surfaces via bioorthogonal conjugation. We optimize the blood and vascular cell compatibilities of the grafted surfaces through changing the SeCA/TPS feeding ratios. At the optimal ratio of 2:2, the surface-engineered stents demonstrate superior inhibition of thrombosis and SMC migration and proliferation, promotion of EPC recruitment, adhesion, and proliferation, as well as prevention of in-stent restenosis (ISR). Overall, our biomimetic surface engineering strategy represents a promising solution to address clinical complications of cardiovascular stents and other blood-contacting metal materials.

Co-Delivery of Paclitaxel and Doxorubicin by pH-Responsive Prodrug Micelles for Cancer Therapy

Background

It is of great significance to develop intelligent co-delivery systems for cancer chemotherapy with improved therapeutic efficacy and few side-effects.

Materials and Methods

Here, we reported a co-delivery system based on pH-sensitive polyprodrug micelles for simultaneous delivery of doxorubicin (DOX) and paclitaxel (PTX) as a combination chemotherapy with pH-triggered drug release profiles. The physicochemical properties, drug release profiles and mechanism, and cytotoxicity of PTX/DOX-PMs have been thoroughly investigated.

Results and Discussion

The pH-sensitive polyprodrug was used as nanocarrier, and PTX was encapsulated into the micelles with high drug-loading content (25.6%). The critical micelle concentration (CMC) was about 3.16 mg/L, indicating the system could form the micelles at low concentration. The particle size of PTX/DOX-PMs was 110.5 nm, and increased to approximately 140 nm after incubation for 5 days which showed that the PTX/DOX-PMs had high serum stability. With decrease in pH value, the particle size first increased, and thenwas no longer detectable. Similar change trend was observed for CMC values. The zetapotential increased sharply with decrease in pH. These results demonstrated the pHsensitivity of PTX/DOX-PMs. In vitro drug release experiments and study on release mechanism showed that the drug release rate and accumulative release for PTX and DOX were dependent on the pH, showing the pH-triggered drug release profiles. Cytotoxicity assay displayed that the block copolymer showed negligible cytotoxicity, while the PTX/DOX-PMs possessed high cytotoxic effect against several tumor cell lines compared with free drugs and control.

Conclusion

All the results demonstrated that the co-delivery system based on pH-sensitive polyprodrug could be a potent nanomedicine for combination cancer chemotherapy. In addition, construction based on polyprodrug and chemical drug could be a useful method to prepare multifunctional nanomedicine.

A Versatile Surface Bioengineering Strategy Based on Mussel-Inspired and Bioclickable Peptide Mimic

In this work, we present a versatile surface engineering strategy by the combination of mussel adhesive peptide mimicking and bioorthogonal click chemistry. The main idea reflected in this work derived from a novel mussel-inspired peptide mimic with a bioclickable azide group (i.e., DOPA₄-azide). Similar to the adhesion mechanism of the mussel foot protein (i.e., covalent/noncovalent comediated surface adhesion), the bioinspired and bioclickable peptide mimic DOPA₄-azide enables stable binding on a broad range of materials, such as metallic, inorganic, and organic polymer substrates. In addition to the material universality, the azide residues of DOPA₄-azide are also capable of a specific conjugation of dibenzylcyclooctyne- (DBCO-) modified bioactive ligands through bioorthogonal click reaction in a second step. To demonstrate the applicability of this strategy for diversified biofunctionalization, we bioorthogonally conjugated several typical bioactive molecules with DBCO functionalization on different substrates to fabricate functional surfaces which fulfil essential requirements of biomedically used implants. For instance, antibiofouling, antibacterial, and antithrombogenic properties could be easily applied to the relevant biomaterial surfaces, by grafting antifouling polymer, antibacterial peptide, and NO-generating catalyst, respectively. Overall, the novel surface bioengineering strategy has shown broad applicability for both the types of substrate materials and the expected biofunctionalities. Conceivably, the "clean" molecular modification of bioorthogonal chemistry and the universality of mussel-inspired surface adhesion may synergically provide a versatile surface bioengineering strategy for a wide range of biomedical materials.

Antifouling and pH-Responsive Poly(Carboxybetaine)-Based Nanoparticles for Tumor Cell Targeting

Nanocarriers with responsibility and surface functionality of targeting molecules have been widely used to improve therapeutic efficiency. Hence, we report the assembly of pH-responsive and targeted polymer nanoparticles (NPs) composed of poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) as the core and poly(carboxybetaine methacrylate) (PCBMA) as the shell, functionalized with cyclic peptides containing Arginine-Glycine-Aspartic acid-D-Phenylalanine-Lysine (RGD). The resulting polymer NPs (PDPA@PCBMA-RGD NPs) can maintain the pH-responsivity of PDPA (pKa ~6.5) and low-fouling property of PCBMA that significantly resist non-specific interactions with RAW 264.7 and HeLa cells. Meanwhile, PDPA@PCBMA-RGD NPs could specifically target αvβ3 integrin-expressed human glioblastoma (U87) cells. The pH-responsiveness and low-fouling properties of PDPA@PCBMA NPs are comparable to PDPA@poly(ethylene glycol) (PDPA@PEG) NPs, which indicates that PCBMA is an alternative to PEG for low-fouling coatings. The advantage of PDPA@PCBMA NPs lies in the presence of carboxyl groups on their surfaces for further modification (e.g., RGD functionalization for cell targeting). The reported polymer NPs represent a new carrier that have the potential for targeted therapeutic delivery.

A Magnetic Dynamic Microbiointerface with Biofeedback Mechanism for Cancer Cell Capture and Release

Dynamic biointerfaces with reversible surface bioactivities enable dynamic modulation of cell-material interactions, thus attracting great attention in biomedical science. Herein, we demonstrated a paradigm shift of dynamic biointerfaces from macroscopical substrates to micron-sized particles by reversible engineering of a phenylboronic acid (PBA)-functionalized magnetic microbead with mussel-inspired cancer cell-targeting peptide. Due to reversible catechol-boronate interactions between the peptides and microbeads, the micron-sized dynamic biointerface exhibited sugar-responsive cancer-targeting activity, showing the potential as a microplatform for magnetic and noninvasive isolation of cancer cells through natural biofeedback mechanism (e.g., human glycemic volatility). Our results demonstrated that the dynamic magnetic platform was capable of selective cancer cell capture (∼85%) and sugar-triggered release of them (>93%) in cell culture medium with high efficiency. More importantly, by using this platform, a decent number of target cells (∼23 on average) could be magnetically isolated and identified from artificial CTC blood samples (1 mL) spiked with 100 cancer cells. In view of the biomimetic nature, high capture efficiency, excellent selectivity, and superiority in cell separation and purification processes, the dynamic magnetic microplatform reported here would be a promising and general tool for rare cell detection and separation and cell-based disease diagnosis.

Bioinspired Surface Functionalization of Titanium Alloy for Enhanced Lubrication and Bacterial Resistance

In clinics it is extremely important for implanted devices to achieve the property of enhanced lubrication and bacterial resistance; however, such a strategy has rarely been reported in previous literature. In the present study, a surface functionalization method, motivated by articular cartilage-inspired superlubrication and mussel-inspired adhesion, was proposed to modify titanium alloy (Ti6Al4V) using the copolymer (DMA-MPC) synthesized via free radical copolymerization. The copolymer-coated Ti6Al4V (Ti6Al4V@DMA-MPC) was evaluated by X-ray photoelectron spectroscopy, water contact angle, and Raman spectra to confirm that the DMA-MPC copolymer was successfully coated onto the Ti6Al4V substrate. In addition, the tribological test, with the polystyrene microsphere and Ti6Al4V or Ti6Al4V@DMA-MPC as the tribopair, indicated that the friction coefficient was greatly reduced for Ti6Al4V@DMA-MPC. Furthermore, the bacterial resistance test showed that bacterial attachment was significantly inhibited for Ti6Al4V@DMA-MPC for the three types of bacteria tested. The enhanced lubrication and bacterial resistance of Ti6Al4V@DMA-MPC was due to the tenacious hydration shell formed surrounding the zwitterionic charges in the phosphorylcholine group of the DMA-MPC copolymer. In summary, a bioinspired surface functionalization strategy is developed in this study, which can act as a universal and promising method to achieve enhanced lubrication and bacterial resistance for biomedical implants.