Plasmonic, Targeted, and Dual Drugs-Loaded Polypeptide Composite Nanoparticles for Synergistic Cocktail Chemotherapy with Photothermal Therapy

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

Dual-Ligand Synergistic Targeting Anti-Tumor Nanoplatforms with Cascade-Responsive Drug Release

Dual-ligand targeting drug delivery nanoplatforms are considered a promising tool for enhancing the specificity of chemotherapy. However, serious off-target delivery has been observed in current dual-ligand targeting nanoplatforms, as each ligand can independently recognize receptors on the cell membrane surface and guide drug nanocarriers to different cells. To overcome this barrier, a dual-ligand synergistic targeting (DLST) nanoplatform is developed, which can guide chemotherapy treatment specifically to cancer cells simultaneously overexpressing two receptors. This nanoplatform consists of a singlet oxygen (¹O₂) photosensitizer-loaded nanocarrier and a drug-loaded nanocarrier with ¹O₂ responsiveness, which were, respectively, decorated with a pair of complementary DNA sequences and two different ligands. For cancer cells overexpressing both receptors, two nanocarriers can be internalized in larger quantities to cause DNA hybridization-induced nanocarrier aggregation, which further activates ¹O₂-triggered drug release under light irradiation. For cells overexpressing a single receptor, only one type of nanocarrier can be internalized in a large quantity, leading to blocked drug release due to the ultrashort action radius of ¹O₂. In vivo evaluation showed this DLST nanoplatform displayed highly specific tumor treatment with minimized long-term toxicity. This is a highly efficient drug delivery system for DLST chemotherapy, holding great potential for clinical applications.

Carbohydrate ligands-directed active tumor targeting of combinatorial chemotherapy/phototherapy-based nanomedicine: A review

Phototherapies or light mediated therapies, including mutually photothermal and photodynamic therapy that encompass irradiation of the target organs with light, have been widely employed as minimally invasive approach associated with negligible drug resistance for eradicating multiple tumors with minimal hazards to normal organs. Despite all these advantages, many obstacles in phototherapy hinder progress toward clinical application. Therefore, researchers have developed nano-particulate delivery systems integrated with phototherapy and therapeutic cytotoxic drugs to overcome these obstacles and achieve maximum efficacy in cancer treatment. Active targeting ligands were integrated into their surfaces to improve the selectivity and tumor targeting ability, enabling easy binding and recognition by cellular receptors overexpressed on the tumor tissue compared to normal ones. This enhances intratumoral accumulation with minimal toxicity on the adjacent normal cells. Various active targeting ligands, including antibodies, aptamers, peptides, lactoferrin, folic acid and carbohydrates, have been explored for the targeted delivery of chemotherapy/phototherapy-based nanomedicine. Among these ligands, carbohydrates have been applied due to their unique features that ameliorate the bioadhesive, noncovalent conjugation to biological tissues. In this review, the up-to-date techniques of employing carbohydrates active targeting ligands will be highlighted concerning the surface modification of the nanoparticles for ameliorating the targeting ability of the chemo/phototherapy.

A self-crosslinking nanogel scaffold for enhanced catalytic efficiency and stability

We report a facile and efficient approach to prepare multifunctional bioinspired platforms under mild conditions that offer increased catalytic efficiency and stability.

Cyclodextrin-Based Nanoplatforms for Tumor Phototherapy: An Update

Tumor phototherapies are light-mediated tumor treatment modalities, which usually refer to tumor photothermal therapy (PTT) and photodynamic therapy (PDT). Due to the outstanding spatial-temporal control over treatment through light irradiation, tumor phototherapies display extremely low side effects during treatment and are believed to be a tumor treatment method with a clinical translation potential. However, current tumor phototherapy nanoplatforms face obstacles, including light irradiation-induced skin burning, tumor hypoxia microenvironments, limited light penetration depth, et al. Therefore, one important research direction is developing a tumor phototherapy nanoplatform with multifunctionality and enhanced pharmacological effects to overcome the complexity of tumor treatment. On the other hand, cyclodextrins (CDs) are starch-originated circular oligosaccharides with negligible toxicity and have been used to form supermolecular nanostructures through a host–guest interaction between the inner cavity of CDs and functional biomolecules. In the past few years, numerous studies have focused on CD-based multifunctional tumor phototherapy nanoplatforms with an enhanced photoeffect, responsive morphological transformation, and elevated drug bioavailability. This review focuses on the preparation methods of CD-based tumor phototherapy nanoplatforms and their unique physiochemical properties for improving anti-tumor pharmacological efficacy.

Thioether-based ROS responsive polymers for biomedical applications

Reactive oxygen species (ROS) play a key role in several biological functions of living organisms such as regulation of cell signalling, production of some hormones, modulation of protein function or mediation of inflammation. In this regard, ROS responsive polymers are ideal candidates for the development of stimuli-responsive biomaterials for target therapies. Among different ROS-responsive polymers, those containing thioether groups are widely investigated in the biomedical field due to their hydrophobic to hydrophilic phase transition under oxidative conditions. This feature makes them able to self-assemble in aqueous solutions forming micellar-type nanoparticles or hydrogels to be mainly used as drug carriers for local therapies in damaged body areas characterized by high ROS production. This review article collects the main findings about the synthesis of thioether-based ROS responsive polymers and polypeptides, their self-assembly properties and ROS responsive behaviour for use as injectable nanoparticles or hydrogels. Afterward, the foremost applications of the thioether-based ROS responsive nanoparticles and hydrogels in the biomedical field, where cancer therapies are a key objective, will be discussed.

Biomimetic nanoprobe-augmented triple therapy with photothermal, sonodynamic and checkpoint blockade inhibits tumor growth and metastasis

Background

Comprehensive antitumor therapy through integrated multimodal means has drawn increasing attention owing to its high efficiency and metastasis suppression.

Results

We describe a synergistic triple protocol combining photothermal and sonodynamic therapy (PTT and SDT), together with immune checkpoint blockade for the inhibition of breast cancer growth and metastases in the 4T1 mouse model. PTT and SDT are synergistically augmented by a novel multimodal imaging nanoprobe integrated with cancer cell membrane-biomimetic nanoparticles (CHINPs) loaded with superparamagnetic iron oxide (SPIO) and hematoporphyrin monomethyl ether (HMME). CHINPs exhibit excellent homologous tumor targeting, and are sequentially triggered by ultrasound and near infrared (NIR) light under the guidance of magnetic resonance, photoacoustic and photothermal imaging, leading to complete in situ tumor eradication and systemic anti-tumor immune activation. Further combination of this approach with immune checkpoint blockade therapy is shown to suppress tumor metastasis.

Conclusion

This work provides proof-of-principle for triple therapy using multimodal imaging-guided PTT/SDT based on biomimetic nanoprobes in combination with immunotherapy to eliminate tumors.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01287-y.

Tumor Microenvironment-Responsive Polypeptide Nanogels for Controlled Antitumor Drug Delivery

Tumor microenvironment-responsive polypeptide nanogels belong to a biomaterial with excellent biocompatibility, easily adjustable performance, biodegradability, and non-toxic properties. They are developed for selective delivery of antitumor drugs into target organs to promote tumor cell uptake, which has become an effective measure of tumor treatment. Endogenous (such as reduction, reactive oxygen species, pH, and enzyme) and exogenous (such as light and temperature) responsive nanogels can release drugs in response to tumor tissues or cells to improve drug distribution and reduce drug side effects. This article systematically introduces the research progress in tumor microenvironment-responsive polypeptide nanogels to deliver antitumor drugs and provides a reference for the development of antitumor nanoformulations.

Ultrasmall Zwitterionic Polypeptide-Coordinated Nanohybrids for Highly Efficient Cancer Photothermal Ferrotherapy

Ferroptosis therapy (FT) based on the Fenton reaction of ferrous nanoparticles has been becoming a unique strategy for cancer treatment; however, current ferrous nanoparticles suffer from slower Fenton reaction kinetics, lower ferroptosis efficacy, and long-term toxicity, so it is urgent to construct biocompatible ferrous nanomaterials with highly efficient Fenton reaction activity for cancer FT. Inspired by single-atom catalysis and size-determined tumor penetration, we conceived an innovative strategy for constructing ultrasmall zwitterionic polypeptide-coordinated nanohybrids of PCGA@FeNP with about 6 nm by utilizing thiol/hydroxyl-iron cooperative coordination chemistry. The ultrasmall size, unsaturated ferrous coordination, and intracellular acidic pH could accelerate the Fenton reaction, thus boosting the efficacy of ferroptosis. Moreover, those coordinated nanohybrids exhibited prominent photothermia with 59.5% conversion efficiency, further accelerating the Fenton reaction and inducing a synergistic effect between FT and photothermal therapy (PTT). In vitro and in vivo GPX-4 expression ascertained that PCGA@FeNP indeed induced effective FT and synergistic FT-PTT. Remarkably, in vivo FT-PTT completely ablated 4T1 solid tumors by one treatment, presenting outstanding and synergistic antitumor efficacy via the photothermia-boosted ferroptosis and apoptosis pathways. This work supplies a practicable strategy to fabricate ultrasmall zwitterionic coordination nanohybrids for highly efficient cancer FT and FT-PTT theranostics with potential clinical transitions.

Supramolecular peptide nano-assemblies for cancer diagnosis and therapy: from molecular design to material synthesis and function-specific applications

Peptide molecule has high bioactivity, good biocompatibility, and excellent biodegradability. In addition, it has adjustable amino acid structure and sequence, which can be flexible designed and tailored to form supramolecular nano-assemblies with specific biomimicking, recognition, and targeting properties via molecular self-assembly. These unique properties of peptide nano-assemblies made it possible for utilizing them for biomedical and tissue engineering applications. In this review, we summarize recent progress on the motif design, self-assembly synthesis, and functional tailoring of peptide nano-assemblies for both cancer diagnosis and therapy. For this aim, firstly we demonstrate the methodologies on the synthesis of various functional pure and hybrid peptide nano-assemblies, by which the structural and functional tailoring of peptide nano-assemblies are introduced and discussed in detail. Secondly, we present the applications of peptide nano-assemblies for cancer diagnosis applications, including optical and magnetic imaging as well as biosensing of cancer cells. Thirdly, the design of peptide nano-assemblies for enzyme-mediated killing, chemo-therapy, photothermal therapy, and multi-therapy of cancer cells are introduced. Finally, the challenges and perspectives in this promising topic are discussed. This work will be useful for readers to understand the methodologies on peptide design and functional tailoring for highly effective, specific, and targeted diagnosis and therapy of cancers, and at the same time it will promote the development of cancer diagnosis and therapy by linking those knowledges in biological science, nanotechnology, biomedicine, tissue engineering, and analytical science.

Design, synthesis and biological applications of glycopolypeptides

Carbohydrates play essential structural and biochemical roles in all living organisms. Glycopolymers are attractive as well-defined biomimetic analogs to study carbohydrate-dependent processes, and are widely applicable biocompatible materials in their own right. Glycopolypeptides have shown great promise in this area since they are closer structural mimics of natural glycoproteins than other synthetic glycopolymers and can serve as carriers for biologically active carbohydrates. This review highlights advances in the area of design and synthesis of such materials, and their biomedical applications in therapeutic delivery, tissue engineering, and beyond.

Endogenous mRNA Triggered DNA-Au Nanomachine for In Situ Imaging and Targeted Multimodal Synergistic Cancer Therapy

The development of versatile nanotheranostic platforms that integrate both diagnostic and therapeutic functions have always been an intractable challenge in precise cancer treatment. Herein, an aptamer-tethered deoxyribonucleic acids-gold particle (Apt-DNA-Au) nanomachine has been developed for in situ imaging and targeted multimodal synergistic therapy of mammary carcinoma. Upon specifically internalized into MCF-7 cells, the tumor-related TK1 mRNA activates the Apt-DNA-Au nanomachine by DNA strand displacement cascades, resulting in the release of the fluorophore and antisense DNA as well as the aggregation of AuNPs for in situ imaging, suppression of survivin expression and photothermal therapy, respectively. Meanwhile, the controlled released drugs are used for chemotherapy, while under the laser irradiation the loaded photosensitizer produces reactive oxygen species (ROS) for photodynamic therapy. The results confirm that the proposed Apt-DNA-Au nanomachine provides a powerful nanotheranostic platform for in situ imaging-guided combinatorial anticancer therapy.

A PEGylated photosensitizer-core pH-responsive polymeric nanocarrier for imaging-guided combination chemotherapy and photodynamic therapy

A novel chemo-photodynamic combined therapeutic self-assembly polymeric platform (MPEG-Hyd-Br₂-BODIPY) was constructed which can encapsulate DOX and exhibited an accelerated release rate with decreasing pH value which results in considerable time/dose-dependent cytotoxicity.

Theranostic Nanoparticles with Aggregation-Induced Emission and MRI Contrast Enhancement Characteristics as a Dual-Modal Imaging Platform for Image-Guided Tumor Photodynamic Therapy

Introduction

Advanced tumor-targeted theranostic nanoparticles play a key role in tumor diagnosis and treatment research. In this study, we developed a multifunctional theranostic platform based on an amphiphilic hyaluronan/poly-(N-ε-carbobenzyloxy-L-lysine) derivative (HA-g-PZLL), superparamagnetic iron oxide (SPIO) and aggregation-induced emission (AIE) nanoparticles for tumor-targeted magnetic resonance (MR) and fluorescence (FL) dual-modal image-guided photodynamic therapy (PDT).

Materials and Methods

The amphiphilic hyaluronan acid (HA) derivative HA-g-PZLL was synthesized by grafting hydrophobic poly-(N-ε-carbobenzyloxy-L-lysine) (PZLL) blocks onto hyaluronic acid by a click conjugation reaction. The obtained HA-g-PZLLs self-assembled into nanoparticles in the presence of AIE molecules and SPIO nanoparticles to produce tumor-targeted theranostic nanoparticles (SPIO/AIE@HA-g-PZLLs) with MR/FL dual-modal imaging ability. Cellular uptake of the theranostic nanoparticles was traced by confocal laser scanning microscopy (CLSM), flow cytometry and Prussian blue staining. The intracellular reactive oxygen species (ROS) generation characteristics of the theranostic nanoparticles were evaluated with CLSM and flow cytometry. The effect of PDT was evaluated by cytotoxicity assay. The dual-mode imaging ability of the nanoparticles was evaluated by a real-time near-infrared fluorescence imaging system and magnetic resonance imaging scanning.

Results

The resulting theranostic nanoparticles not only emit red fluorescence for high-quality intracellular tracing but also effectively produce singlet oxygen for photodynamic tumor therapy. In vitro cytotoxicity experiments showed that these theranostic nanoparticles can be efficiently taken up and are mainly present in the cytoplasm of HepG2 cells. After internalization, these theranostic nanoparticles showed serious cytotoxicity to the growth of HepG2 cells after white light irradiation.

Discussion

This work provides a simple method for the preparation of theranostic nanoparticles with AIE characteristics and MR contrast enhancement, and serves as a dual-modal imaging platform for image-guided tumor PDT.

Morphological Transitions of Photoresponsive Vesicles from Amphiphilic Polypeptoid Copolymers for Controlled Release

Photoresponsive polymers have attracted increasing interest for a variety of applications. Here, we report a family of photoresponsive polypeptoid-based copolymer poly(ethylene glycol)-b-poly(N-(S-(o-nitrobenzyl)-thioethyl) glycine)-co-poly(N-(2-phenylethyl) glycine) (PEG-b-PNSN-co-PNPE) synthesized by the controlled ring-opening polymerization (ROP) technique. The key feature of the design is to incorporate both o-nitrobenzyl group moiety to offer the photoresponsive property and phenethyl residues to tune the structural and amphiphilic property of the system. We demonstrate that the cleavage degree of the o-nitrobenzyl group can reach to 100% upon UV-irradiation. With delicate design, a photoresponsive vesicle-to-sphere transition has been observed that facilitates the release of the encapsulants. This work provides a facile approach to prepare a type of photoresponsive polymers with tunable properties for drug delivery.

Zwitterionic polypeptide nanomedicine with dual NIR/reduction-responsivity for synergistic cancer photothermal-chemotherapy

Dual NIR/reduction-responsive and zwitterionic polypeptide nanoparticles of PMC/DOX-ICG were fabricated, which achieved in vivo NIR fluorescence imaging and synergistic cancer PTT-CT treatment, and effectively ablated the HeLa tumors without recurrence for 30 days.

Therapeutic polymeric nanomedicine: GSH-responsive release promotes drug release for cancer synergistic chemotherapy

To obtain an efficient dual-drug release and enhance therapeutic efficiency for combination chemotherapy, a glutathione (GSH)-responsive therapeutic amphiphilic polyprodrug copolymer (mPEG-b-PCPT) is synthesized to load doxorubicin (DOX) via hydrophobic and π–π stacking interaction. In this nanomedicine system (mPEG-b-PCPT/DOX), the ratio of the two drugs can be easily modulated by changing the loading content of DOX. The in vitro drug release curves and laser confocal images suggested that the release of CPT and DOX is induced through a “release promotes release strategy”: after internalization into tumor cells, the disulfide bonds in the nanomedicine are cleaved by glutathione (GSH) in the cytoplasm and then lead to the release of CPT. Meanwhile, the disassembly of nanomedicine immediately promotes the co-release of DOX. The optimum dose ratio of CPT and DOX is evaluated via the combination index (CI) value using HepG-2 cells. The results of cell apoptosis and cell viability prove the better synergistic efficiency of the nanomedicine than free drugs at the optimum dose ratio of 1. Consequently, this stimuli-responsive synergistic chemotherapy system provides a direction for the fabrication of nanomedicines possessing promising potential in clinical trials.

In the GSH-responsive doxorubicin loading camptothecin prodrug nanomedicine, easy modulation of the dose ratio and controlled co-release were achieved, and the synergistic effect was significantly improved.

One-pot synthesis of acid-induced in situ aggregating theranostic gold nanoparticles with enhanced retention in tumor cells

In this work, we took advantage of a one-pot reaction to prepare tumor-targeting nanoparticles (Au@T), which could respond to the intracellular acidic environment and form aggregates to enhance the retention effect of nanoparticles in tumor cells, for tumor dual-mode diagnose and photothermal therapy.

HP-β-CD Functionalized Fe3O4/CNPs-Based Theranostic Nanoplatform for pH/NIR Responsive Drug Release and MR/NIRFL Imaging-Guided Synergetic Chemo/Photothermal Therapy of Tumor

The combination of chemotherapy and photothermal therapy has aroused great interest due to its better antitumor effect than either single therapy alone. Herein, we report on the development of hydroxypropyl-β-cyclodextrin functionalized Fe₃O₄/carbon nanoparticles (HFCNPs) for pH/near-infrared (NIR) responsive drug release, magnetic resonance/NIR fluorescence (MR/NIRFL) imaging-guided combined chemo/photothermal therapy. The high doxorubicin (DOX) loading capacity (61.2%) and controlled drug release by NIR irradiation and weak acid microenvironment render HFCNPs a good vector for DOX delivery and controlled release. Moreover, the MR/NIRFL dual-modal imaging was used to define the tumor location, size, and boundary and to track the tumor accumulation of HFCNPs and their biodistribution. The efficient accumulation and prolonged retention time of the nanoparticles in tumor are beneficial to tumor therapy. Taking advantage of the NIR laser-induced heating and hence promoted drug permeation, remarkable tumor inhibition was realized by synergetic chemo/photothermal therapy. In conclusion, the current work offers a promising approach to the development of smart and efficient multimodal cancer-targeted nanotheranostics.

Noninvasive photothermal cancer therapy nanoplatforms via integrating nanomaterials and functional polymers

In the cutting-edge field of cancer therapy, noninvasive photothermal therapy (PTT) has received great attention because it is considered to overcome the drawbacks of conventional surgery, radiotherapy and chemotherapy of severe body injuries and side effects on the immune system. The construction of PTT therapeutic and theranostic nanoplatforms is the key issue in achieving tumor targeting, imaging and therapy in a synergetic manner. In this review, we focus on the recent advances in constructing PTT therapeutic and theranostic nanoplatforms by integrating nanomaterials and functional polymers. The noninvasive photothermal cancer therapy mechanism and achievement strategies of PTT therapeutic and theranostic nanoplatforms are presented as well as the innovative construction strategies and perspectives for the future. Owing to their high tumor ablation efficiency, biological availability and low- or non-toxicity, PTT therapeutic and theranostic nanoplatforms are promising and emerging in medicine and clinical applications.

Electronic Structure of a Self-Assembled Monolayer with Two Surface Anchors: 6-Mercaptopurine on Au(111)

The electronic structure of aromatic and aliphatic thiols on Au(111) has been extensively studied in relation to possible applications in molecular electronics. In this work, the effect on the electronic structure of an additional anchor to the S-Au bond using 6-mercaptopurine as a model system has been investigated. Results from X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory (DFT) confirm that this molecule adsorbs on Au(111) with S-Au and iminic N-Au bonds. Combined ultraviolet photoelectron spectroscopy and DFT data reveal that formation of the 6MP self-assembled monolayer generates a molecular dipole perpendicular to the surface, with negative charges residing at the metal/monolayer interface and positive charges at the monolayer/vacuum interface, which lowers the substrate work function. Scanning tunneling microscopy shows two surface molecular domains: a well-ordered rectangular lattice where molecules are tilted on average 30° with respect to the substrate and aligned 6MP islands where molecules are standing upright. Finally, we found a new electronic state located at -1.7 eV with respect to the Fermi level that corresponds to a localized π molecular state, while the state corresponding to the N-Au bond is hybridized with Au d electrons and stabilized at much lower energies (-3 eV).

Design and fabrication of poly(HPMA)–6-mercaptopurine conjugates and their in vitro anticancer effect

A polymeric prodrug of poly(HPMA)–6MP was synthesized by grafting 6MP on poly(HPMA) and it exhibited an enhanced therapeutic effect.

Hyaluronic Acid-Functionalized Gold Nanorods with pH/NIR Dual-Responsive Drug Release for Synergetic Targeted Photothermal Chemotherapy of Breast Cancer

Tumor-targeted delivery of photothermal agent and controlled release of concomitant chemotherapeutic drug are two key factors for combined photothermal chemotherapy. Herein, we developed a pH/near-infrared (NIR) dual-triggered drug release nanoplatform based on hyaluronic acid (HA)-functionalized gold nanorods (GNRs) for actively targeted synergetic photothermal chemotherapy of breast cancer. Targeting folate (FA), dopamine, and adipic acid dihydrazide triconjugated HA was first synthesized and used to decorate GNRs via Au-catechol bonds, and then an anticarcinogen doxorubicin (DOX) was conjugated onto HA moieties via an acid-labile hydrazone linkage, resulting in multifunctional nanoparticles GNRs-HA-FA-DOX. The nanoparticles exhibited excellent stability and had a pH and NIR dual-responsive drug release behavior. In vitro studies showed that the nanoparticles could be efficiently internalized into breast cancer MCF-7 cells and kill them under NIR irradiation in a synergistic fashion via inducing cell apoptosis. Pharmacokinetics and biodistribution studies in tumor-bearing mice indicated that the nanoparticles had a long blood circulation with a half-life of 2.4 h and exhibited a high accumulation of 11.3% in tumor site. The tumors of mice treated with combined chemotherapy and photothermal therapy were completely suppressed without obvious systemic toxicity after 20 d of treatment. These results demonstrated a great potential of GNRs-HA-FA-DOX nanoparticles for targeted synergistic therapy of breast cancer.

Synthesis and Application of Aurophilic Poly(Cysteine) and Poly(Cysteine)-Containing Copolymers

The redox capacity, as well as the aurophilicity of the terminal thiol side groups, in poly(Cysteine) lend a unique characteristic to this poly(amino acid) or polypeptide. There are two major application fields for this polymer: (i) biomedical applications in drug delivery and surface modification of biomedical devices and (ii) as coating for electrodes to enhance their electrochemical sensitivity. The intended application determines the synthetic route for p(Cysteine). Polymers to be used in biomedical applications are typically polymerized from the cysteine N-carboxyanhydride by a ring-opening polymerization, where the thiol group needs to be protected during the polymerization. Advances in this methodology have led to conditions under which the polymerization progresses as living polymerization, which allows for a strict control of the molecular architecture, molecular weight and polydispersity and the formation of block copolymers, which eventually could display polyphilic properties. Poly(Cysteine) used as electrode coating is typically polymerized onto the electrode by cyclic voltammetry, which actually produces a continuous, pinhole-free film on the electrode via the formation of covalent bonds between the amino group of Cysteine and the carbon of the electrode. This resulting coating is chemically very different from the well-defined poly(Cysteine) obtained by ring-opening polymerizations. Based on the structure of cysteine a significant degree of cross-linking within the coating deposited by cyclic voltammetry can be assumed. This manuscript provides a detailed discussion of the ring-opening polymerization of cysteine, a brief consideration of the role of glutathione, a key cysteine-containing tripeptide, and examples for the utilization of poly(Cysteine) and poly(Cysteine)-containing copolymers, in both, the biomedical as well as electrochemical realm.

Biopolymer-Drug Conjugate Nanotheranostics for Multimodal Imaging-Guided Synergistic Cancer Photothermal-Chemotherapy

Some of the biomedical polymer-drug conjugates are being translated into clinical trials; however, they intrinsically lack photothermal and multi-imaging capabilities, hindering them from imaging-guided precision cancer therapy and complete tumor regression. We introduce a new concept of all-in-one biopolymer-drug conjugate nanotheranostics and prepare a kind of intracellular pH-sensitive polydopamine-doxorubicin (DOX) conjugate nanoparticles (PDCNs) under mild conditions. Significantly, this strategy integrates polymeric prodrug-induced chemotherapy (CT), near-infrared (NIR) light-mediated photothermal therapy (PT), and triple modalities including DOX self-fluorescence, photothermal, and photoacoustic (PA) imaging into one conjugate nanoparticle. The PDCNs present excellent photothermal property, dual stimuli-triggered drug release behavior, and about 12.4-fold blood circulation time compared to free DOX. Small animal fluorescent imaging technique confirms that PDCNs have preferential tumor accumulation effect in vivo, giving a 12.8-fold DOX higher than the control at 12 h postinjection. Upon NIR laser irradiation (5 min, 808 nm, and 2 W·cm^-2), the PDCN-mediated photothermal effect can quickly elevate the tumor over 50 °C, exhibiting good photothermal and PA imaging functions, of which the PA amplitude is 3.6-fold greater than the control. In vitro and in vivo assays persuasively verify that intravenous photothermal-CT of PDCNs produces synergistic antitumor activity compared to single PT or CT, achieving complete tumor ablation during the evaluation period.

Stepwise growth of gold coated cancer targeting carbon nanotubes for the precise delivery of doxorubicin combined with photothermal therapy

Combining doxorubicin with thermal therapy in the clinic has led to startling results in the treatment of problematic cancers. Here, we describe a multimodal multi-walled carbon nanotube material that combines tumor targeting, doxorubicin delivery, and photothermal therapy for localized cancer treatment. The agent was constructed layer-by-layer from polypyrrole and gold nanoparticles on multi-walled carbon nanotubes. The gold surface was modified with tumor targeting folic acid terminated PEGylated chains, which also provide water-dispersibility, biocompatibility and should extend the half-life in blood. The material has a high loading/unloading capacity for the cytotoxic agent doxorubicin. Release of the doxorubicin, combined with the photothermal properties of the material that induces localized hyperthermia, leads to efficient cancer cell death.

Self-assembled DNA nanowires as quantitative dual-drug nanocarriers for antitumor chemophotodynamic combination therapy

Self-assembled DNA nanowires were fabricated through a supersandwich hybridization reaction and co-loaded with a photosensitizer chlorin e6 (Ce6) and a chemotherapeutic drug doxorubicin (DOX) for antitumor chemophotodynamic combination therapy.