CXCR4-Mediated Codelivery of FLT3 and BCL-2 Inhibitors for Enhanced Targeted Combination Therapy of FLT3-ITD Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is often associated with poor prognosis and survival. Small molecule inhibitors, though widening the treatment landscape, have limited monotherapy efficacy. The combination therapy, however, shows suboptimal clinical outcomes due to low bioavailability, overlapping systemic toxicity and drug resistance. Here, we report that CXCR4-mediated codelivery of the BCL-2 inhibitor venetoclax (VEN) and the FLT3 inhibitor sorafenib (SOR) via T22 peptide-tagged disulfide cross-linked polymeric micelles (TM) achieves synergistic treatment of FLT3-ITD AML. TM-VS with a VEN/SOR weight ratio of 1/4 and T22 peptide density of 20% exhibited an extraordinary inhibitory effect on CXCR4-overexpressing MV4-11 AML cells. TM-VS at a VEN/SOR dosage of 2.5/10 mg/kg remarkably reduced leukemia burden, prolonged mouse survival, and impeded bone loss in orthotopic MV4-11-bearing mice, outperforming the nontargeted M-VS and oral administration of free VEN/SOR. CXCR4-mediated codelivery of BCL-2 and FLT3 inhibitors has emerged as a prospective clinical treatment for FLT3-ITD AML.

Polyglycerol-Shelled Reduction-Sensitive Polymersome for DM1 Delivery to HER-2-Positive Breast Cancer.

Supramolecular delivery systems with the prolonged circulation, the potential for diverse functionalization, and few toxin-related limitations have been extensively studied. For the present study, we constructed a linear polyglycerol-shelled polymersome attached with the anti-HER-2-antibody trastuzumab. We then covalently loaded the anticancer drug DM1 in the polymersome via dynamic disulfide bonding. The resulted trastuzumab-polymersome-DM1 (Tra-PS-DM1) exhibits a mean size of 95.3 nm and remarkable drug loading efficiency % of 99.3%. In addition to its superior stability, we observed the rapid release of DM1 in a controlled manner under reductive conditions. Compared to the native polymersomes, Tra-PS-DM1 has shown greatly improved cellular uptake and significantly reduced IC50 up to 17-fold among HER-2-positive cancer cells. Moreover, Tra-PS-DM1 demonstrated superb growth inhibition of HER-2-positive tumoroids; specifically, BT474 tumoroids shrunk up to 62% after 12 h treatment. With exceptional stability and targetability, the PG-shelled Tra-PS-DM1 appears as an attractive approach for HER-2-positive tumor treatment.

Advancing Artificial Cells with Functional Compartmentalized Polymeric Systems - In Honor of Wolfgang Meier.

The fundamental building block of living organisms is the cell, which is the universal biological base of all living entities. This micrometric mass of cytoplasm and the membrane border have fascinated scientists due to the highly complex and multicompartmentalized structure. This specific organization enables numerous metabolic reactions to occur simultaneously and in segregated spaces, without disturbing each other, but with a promotion of inter- and intracellular communication of biomolecules. At present, artificial nano- and microcompartments, whether as single components or self-organized in multicompartment architectures, hold significant value in the study of life development and advanced functional materials and in the fabrication of molecular devices for medical applications. These artificial compartments also possess the properties to encapsulate, protect, and control the release of bio(macro)molecules through selective transport processes, and they are capable of embedding or being connected with other types of compartments. The self-assembly mechanism of specific synthetic compartments and thus the fabrication of a simulated organelle membrane are some of the major aspects to gain insight. Considerable efforts have now been devoted to design various nano- and microcompartments and understand their functionality for precise control over properties. Of particular interest is the use of polymeric vesicles for communication in synthetic cells and colloidal systems to reinitiate chemical and biological communication and thus close the gap toward biological functions. Multicompartment systems can now be effectively created with a high level of hierarchical control. In this way, these structures can not only be explored to deepen our understanding of the functional organization of living cells, but also pave the way for many more exciting developments in the biomedical field.

Cetuximab-Polymersome-Mertansine Nanodrug for Potent and Targeted Therapy of EGFR-Positive Cancers.

Targeted nanomedicines particularly armed with monoclonal antibodies are considered to be the most promising advanced chemotherapy for malignant cancers; however, their development is hindered by their instability and drug leakage problems. Herein, we constructed a robust cetuximab-polymersome-mertansine nanodrug (C-P-DM1) for highly potent and targeted therapy of epidermal growth factor receptor (EGFR)-positive solid tumors. C-P-DM1 with a tailored cetuximab surface density of 2 per P-DM1 exhibited a size of ca. 60 nm, high stability with minimum DM1 leakage, glutathione-triggered release of native DM1, and 6.0-11.3-fold stronger cytotoxicity in EGFR-positive human breast (MDA-MB-231), lung (A549), and liver (SMMC-7721) cancer cells (IC50 = 27.1-135.5 nM) than P-DM1 control. Notably, intravenous injection of C-P-DM1 effectively repressed subcutaneous MDA-MB-231 breast cancer and orthotopic A549-Luc lung carcinoma in mice without inducing toxic effects. Strikingly, intratumoral injection of C-P-DM1 completely cured 60% of mice bearing breast tumor without recurrence. This robust cetuximab-polymersome-mertansine nanodrug provides a promising new strategy for targeted treatment of EGFR-positive solid malignancies.

CD38-Directed Vincristine Nanotherapy for Acute Lymphoblastic Leukemia.

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Although intensive chemotherapy greatly improved the survival rate, it is often accompanied by severe and lifelong side effects as a result of weak ALL selectivity. The intensive and poorly selective chemotherapy is also detrimental to patients' immune system. There is an urgent need to develop more selective and less toxic chemotherapy for ALL. Here, we report daratumumab-polymersome-vincristine (DP-VCR) as a CD38-directed nanotherapy for ALL. DP-VCR showed selective uptake in CD38-positive 697 and Nalm-6-Luc ALL cells and potent anti-ALL activity with an IC50 as low as 0.06 nM VCR, which was 13.7-fold more potent than free VCR. In contrast, no toxicity to human peripheral blood mononuclear cells was detected for DP-VCR even at 108.3 nM VCR. The apoptotic assays confirmed a high selectivity of DP-VCR to CD38-positive ALL cells. DP-VCR exhibited superior treatment of both 697 and Nalm-6-Luc orthotopic ALL models to all controls, as revealed by significant survival benefit and marked reduction of leukemia burden in bone marrow, blood, spleen, and liver. Importantly, DP-VCR induced few side effects. DP-VCR emerges as a safe and potent nanotherapy for CD38-positive ALL.

CD44-Targeted Multifunctional Nanomedicines Based on a Single-Component Hyaluronic Acid Conjugate with All-Natural Precursors: Construction and Treatment of Metastatic Breast Tumors in Vivo.

Metastasis is responsible for >90% of the deaths of breast cancer patients in the clinic. Here, we report on cross-linked multifunctional hyaluronic acid nanoparticles carrying docetaxel (DTX-CMHN) for enhanced suppression of highly metastatic 4T1 breast tumors in vivo. DTX-CMHN was formed from a single and all-natural hyaluronic acid-g-polytyrosine-lipoic acid conjugate (HA-g-PTyr-LA; HA, 20 kDa; PTyr, 2.2 kDa), and the size of DTX-CMHN increased from 69 to 78 to 96 nm as the increasing degree of substitution (DS) of PTyr increased from 4 to 11 to 15, respectively. Robust encapsulation of DTX was obtained when DS ≥ 11. DTX-CMHN while steady in a nonreducing environment was destabilized under 10 mM glutathione releasing ∼90% of the DTX within 24 h. It is noteworthy that DTX-CMHN exhibited better antitumor, antimigration, and anti-invasion activity in CD44-overexpressed 4T1-Luc breast cancer cells than free DTX. Interestingly, DTX-CMHN displayed a long elimination half-life of 5.75 h, in contrast to half-lives of 2.11 and 0.75 h for its non-cross-linked counterpart (DTX-MHN) and free DTX, respectively. In vivo therapeutic studies showed significantly better inhibition of primary 4T1-Luc tumor growth and lung metastasis and lower toxicity of DTX-CMHN compared with that of free DTX. These multifunctional nanoformulations based on a single and all-natural hyaluronic acid conjugate emerge as a potential nanoplatform for targeted treatment of CD44-positive metastatic tumors.

Smart Polymersomes Dually Functionalized with cRGD and Fusogenic GALA Peptides Enable Specific and High-Efficiency Cytosolic Delivery of Apoptotic Proteins.

Low cell selectivity and uptake coupled with endosomal entrapment pose critical hurdles for intracellular delivery and clinical translation of therapeutic proteins. Herein, we report that smart polymersomes dually functionalized with cRGD and fusogenic GALA peptides (cRGD/GALA-Ps) enable ανß3-specific and high-efficiency cytosolic delivery of cytochrome C (CC), a model apoptotic protein, to A549 human lung cancer cells. cRGD/GALA-Ps was prepared with 20 mol % cRGD and varying GALA contents from 2 to 4 to 6 mol % via coassembly of PEG- b-poly(trimethylene carbonate- co-dithiolane trimethylene carbonate)-spermine (PEG- b-P(TMC- co-DTC)-spermine), cRGD-PEG- b-P(TMC- co-DTC), and maleimide-PEG- b-P(TMC- co-DTC) and postmodification using GALA-SH (sequence: CWEAALAEALAEALAEHLAEALAEALEALAA). cRGD/GALA-Ps loaded with ∼13 wt % CC displayed a small size of about 65 nm and fast glutathione-triggered protein release. Interestingly, cRGD/GALA-Ps maintained a similar targeting ability to cRGD-Ps in ανß3-positive A549 lung cancer cells, while markedly enhanced cytosolic release of FITC-labeled CC, as revealed by confocal microscopy. MTT assays exhibited that CC-loaded cRGD/GALA-Ps was significantly more potent than CC-loaded cRGD-Ps, in which cell viabilities of 76.2, 51.0, 29.6, and 35.5% were discerned for cRGD/GALA-Ps with 0, 2, 4, and 6 mol % GALA, respectively, at 15.4 µM CC. Apoptosis assays corroborated that cRGD/GALA-Ps-CC with 4 mol % GALA induced better apoptosis of A549 cells than cRGD-Ps-CC (cell apoptosis: 36.4 vs 14.4%). These results highlight that dual-functionalization of polymersomes with targeting and fusogenic peptides provides an appealing strategy for cytosolic protein delivery.

Cancer Nanomedicines Based on Synthetic Polypeptides.

Nanomedicines are deemed as the most promising treatment modality for malignant cancers. Particularly, cancer nanomedicines based on synthetic polypeptides have gained interest because they possess excellent safety, unique hierarchical structure, and tailorable functionalities to suit for delivery of diverse drugs including synthetic drugs, peptides, proteins, and nucleic acids. A few polypeptide-based nanoformulations (e.g., NK105, NC6004, NK911, CT2103) are under phases I-III clinical investigation for treating patients with advanced solid tumors. In recent years, progress has been made in the development of robust and high drug loading, tumor-targeting, membrane-disrupting, and stimuli-sensitive nanomedicines from de novo functional polypeptides, which afford not only better safety and reduced adverse effects, but also further improved anticancer efficacy over clinical formulations. Moreover, virus-mimicking vehicles have been devised from polypeptides for efficient nonviral delivery of highly potent peptides, proteins, and nucleic acids, greatly advancing biotherapy for cancers. In this Perspective, we highlight the state-of-the-art design and fabrication of cancer nanomedicines based on synthetic polypeptides and, at the end, give our viewpoints on their future development for targeted cancer therapy and potential challenges for clinical translation.

HER2-Specific Reduction-Sensitive Immunopolymersomes with High Loading of Epirubicin for Targeted Treatment of Ovarian Tumor.

Monoclonal antibodies can effectively target to tumors in patients, as validated by antibody-drug conjugates (ADCs). The clinically used ADCs, nevertheless, are restricted to toxins only and suffer from low drug content, excessive use of antibody, and high cost. Here, we report on trastuzumab-decorated disulfide-cross-linked polymersomes (Tra-Ps) for specific delivery of epirubicin hydrochloride (EPI·HCl) to HER2-positive SKOV-3 ovarian tumor. EPI·HCl-loaded Tra-Ps (Tra-Ps-EPI) with a small size of 50-60 nm and varying Tra surface densities (0.5 to 2.4 Tra per Ps) were conveniently obtained via post-conjugation of thiolated trastuzumab onto the surface of maleimide-functionalized Ps-EPI with a drug loading content of 12.7 wt %. Interestingly, Tra-Ps with 1.3 trastuzumab on the surface exhibited a 6-fold higher binding affinity to the HER2 extracellular domain than that of native trastuzumab. In vitro studies revealed that Tra-Ps-EPI with long-term storage stability could rapidly release drugs under a reductive condition and efficiently deliver a large amount of EPI·HCl to HER2-positive SKOV-3 cells, leading to stronger cytotoxicity than the nontargeted Ps-EPI. Moreover, Tra-Ps-EPI displayed a long circulation time (ca. 8 h), deep tumor penetration, and superior tumor growth inhibition in SKOV-3 ovarian tumor-bearing nude mice, which were more effective than free EPI·HCl and nontargeted Ps-EPI. These HER2-specific reduction-sensitive immunopolymersomes with high loading of epirubicin emerge as an attractive treatment for HER2-positive tumors.

Integrated Multifunctional Micelles Co-Self-Assembled from Polypeptides Conjugated with Natural Ferulic Acid and Lipoic Acid for Doxorubicin Delivery.

The development of safe, easily accessible, and multifunctional nanocarriers is a big topic in nanomedicine research. Here, integrated multifunctional micelles (IMM) were developed by co-self-assembly of poly(ethylene glycol)-b-poly(l-lysine) derivatives with natural ferulic acid (FA) or lipoic acid (LA). FA confers IMM with intrinsic antitumor activity, improved loading of doxorubicin (DOX) through π-π stacking, and reduced DOX cardiotoxicity. LA provides IMM with reversible crosslinking property, which leads to a high colloidal stability with inhibited drug leakage and triggered intracellular DOX release. Notably, our results showed that cRGD-decorated IMM (cRGD-IMM) had a small size (≈56 nm) and superior loading of DOX (27.1 wt. %). Blank cRGD-IMM, though nontoxic to normal cells, exhibited obvious antiproliferative activity against cancer cells including B16F10 and HCT-116 cells at 150 µg FA equiv. mL-1 . DOX-loaded cRGD-IMM displayed enhanced growth inhibition of αv ß3 -positive B16F10 and HCT-116 cells, a long elimination half-life of 3.85 h, and a high maximum-tolerated dose of over 100 mg DOX equiv. kg-1 . Histological analysis revealed that DOX-loaded cRGD-IMM at 100 mg DOX equiv. kg-1 caused negligible cardiotoxicity, which is a major issue for the clinical use of DOX. These integrated multifunctional micelles with excellent safety and accessibility have emerged as a new platform for targeted cancer chemotherapy.

Cyclic RGD-Peptide-Functionalized Polylipopeptide Micelles for Enhanced Loading and Targeted Delivery of Monomethyl Auristatin E.

Monomethyl auristatin E (MMAE) is an extremely potent peptide drug that is currently used in the form of antibody drug conjugates (ADCs) for treating different cancers. ADCs are, however, associated with low drug conjugation, immunogenicity, small scale production, and high costs. Here, cRGD-functionalized polylipopeptide micelles (cRGD-Lipep-Ms) were explored for enhanced loading and targeted delivery of MMAE to HCT-116 colorectal tumor xenografts. Interestingly, cRGD-Lipep-Ms achieved an MMAE loading content of 5.5 wt %, which was 55-fold higher than that of poly(ethylene glycol)- b-poly(d,l-lactide) micelles. MMAE-loaded cRGD-Lipep-Ms (MMAE-cRGD-Lipep-Ms) showed a small hydrodynamic size of 59 nm, minimal drug leakage in 10% FBS, and efficient uptake and superb antiproliferative activity in αvß5-overexpressing HCT-116 tumor cells. Remarkably, MMAE-cRGD-Lipep-Ms displayed over 10-fold better toleration than free MMAE in mice and completely suppressed growth of HCT-116 colorectal tumor xenografts. These polylipopeptide micelles have appeared to be an attractive alternative to ADCs for targeted delivery of potent peptide drugs.

Construction of Small-Sized, Robust, and Reduction-Responsive Polypeptide Micelles for High Loading and Targeted Delivery of Chemotherapeutics.

Polypeptide micelles, though having been proved to be an appealing nanoplatform for cancer chemotherapy, are met with issues like inefficient drug encapsulation, gradual drug release, and low tumor cell selectivity and uptake. Here, we report on cRGD-decorated, small-sized, robust, and reduction-responsive polytyrosine micelles (cRGD-rPTM) based on poly(ethylene glycol)- b-poly(l-tyrosine)-lipoic acid (PEG- b-PTyr-LA) conjugate for high loading and targeted delivery of doxorubicin (Dox). Notably, cRGD-rPTM exhibited efficient loading of Dox, giving cRGD-rPTM-Dox with a drug loading content (DLC) of 18.5 wt % and a small size of 45 nm at a theoretical DLC of 20 wt %. cRGD-rPTM-Dox displayed reduction-triggered drug release, high selectivity and superior antiproliferative activity toward αvß3 integrin positive MDA-MB-231 breast cancer cells (IC50 = 1.5 µg/mL) to both nontargeted rPTM-Dox and clinical liposomal formulation (LP-Dox). cRGD-rPTM-Dox demonstrated a prolonged circulation time compared with the noncrosslinked cRGD-PTM-Dox control and significantly better accumulation in MDA-MB-231 breast tumor xenografts than nontargeted rPTM-Dox. Moreover, cRGD-rPTM-Dox at 6 mg Dox equiv/kg could remarkably suppress growth of MDA-MB-231 human breast tumor without inducing obvious side effects, outperforming both rPTM-Dox and LP-Dox. These reduction-responsive multifunctional polytyrosine micelles appear to be a viable and versatile nanoplatform for targeted chemotherapy.

Tuning the Properties of Polymer Capsules for Cellular Interactions.

Particle-cell interactions are governed by, among other factors, the composition and surface properties of the particles. Herein, we report the preparation of various polymer capsules with different compositions and properties via atom transfer radical polymerization mediated continuous assembly of polymers (CAPATRP), where the cellular interactions of these capsules, particularly fouling and specific targeting, are examined by flow cytometry and deconvolution microscopy. Acrylated eight-arm poly(ethylene glycol) (8-PEG) and poly(N-(2-hydroxypropyl)-methacrylamide) (PHPMA) as well as methacrylated hyaluronic acid (HA), poly(glutamic acid) (PGA), and poly(methacrylic acid) (PMA) are used as macro-cross-linkers to obtain a range of polymer capsules with different compositions (PEG, PHPMA, HA, PGA, and PMA). Capsules composed of low-fouling polymers, PEG and PHPMA, show negligible association with macrophage Raw 264.7, monocyte THP-1, and HeLa cells. HA capsules, although moderately low-fouling (<22%) to HeLa, BT474, Raw 264.7, and THP-1 cells, exhibit high targeting specificity to CD44-over-expressing MDA-MB-231 cells. In contrast, PGA and PMA capsules show high cellular association toward phagocytic Raw 264.7 and THP-1 cells. These findings demonstrate the capability of the CAPATRP technique in preparing polymer capsules with specific cellular interactions.

Glutathione-Sensitive Hyaluronic Acid-Mercaptopurine Prodrug Linked via Carbonyl Vinyl Sulfide: A Robust and CD44-Targeted Nanomedicine for Leukemia.

6-Mercaptopurine (6-MP) is an essential medicine used for treating leukemia in the clinics. 6-MP suffers, however, from poor water solubility, low bioavailability, and significant side effects. Here, we designed CD44-targeted glutathione-sensitive hyaluronic acid-mercaptopurine prodrug (HA-GS-MP) linked via carbonyl vinyl sulfide for safer and enhanced treatment of acute myeloid leukemia (AML). HA-GS-MP obtained with 50 kDa HA and 6-MP conjugation content of 6.9 wt % showed excellent water solubility with a hydrodynamic size of ca. 15 nm. Intriguingly, HA-GS-MP was extremely stable, without any drug leakage, under physiological environment while rapidly releasing 6-MP in response to 10 mM glutathione. HA-GS-MP exhibited obvious targetability and markedly enhanced antitumor effect to OCI/AML-2 human AML cells (IC50 = 16.9 µg 6-MP equiv./mL). The pharmacokinetic studies displayed that Cy5-labeled HA-GS-MP had a long circulation time in mice (elimination half-life = 4.37 h). The in vivo fluorescence images demonstrated strong and persistent accumulation of Cy5-labeled HA-GS-MP from 4 to 48 h post injection in the subcutaneous OCI/AML-2 tumor in nude mice. Notably, HA-GS-MP while causing little side effects induced significantly enhanced growth inhibition of OCI/AML-2 tumor and better survival rate of OCI/AML-2 tumor-bearing mice as compared to free 6-MP. Carbonyl vinyl sulfide-linked hyaluronic acid-mercaptopurine prodrug has appeared to be a simple and smart nanomedicine for targeted treatment of AML.

cRGD-installed docetaxel-loaded mertansine prodrug micelles: redox-triggered ratiometric dual drug release and targeted synergistic treatment of B16F10 melanoma.

Combinatorial chemotherapy, which has emerged as a promising treatment modality for intractable cancers, is challenged by a lack of tumor-targeting, robust and ratiometric dual drug release systems. Here, docetaxel-loaded cRGD peptide-decorated redox-activable micellar mertansine prodrug (DTX-cRGD-MMP) was developed for targeted and synergistic treatment of B16F10 melanoma-bearing C57BL/6 mice. DTX-cRGD-MMP exhibited a small size of ca. 49 nm, high DTX and DM1 loading, low drug leakage under physiological conditions, with rapid release of both DTX and DM1 under a cytoplasmic reductive environment. Notably, MTT and flow cytometry assays showed that DTX-cRGD-MMP brought about a synergistic antitumor effect to B16F10 cancer cells, with a combination index of 0.37 and an IC50 over 3- and 13-fold lower than cRGD-MMP (w/o DTX) and DTX-cRGD-Ms (w/o DM1) controls, respectively. In vivo studies revealed that DTX-cRGD-MMP had a long circulation time and a markedly improved accumulation in the B16F10 tumor compared with the non-targeting DTX-MMP control (9.15 versus 3.13% ID/g at 12 h post-injection). Interestingly, mice treated with DTX-cRGD-MMP showed almost complete growth inhibition of B16F10 melanoma, with tumor inhibition efficacy following an order of DTX-cRGD-MMP > DTX-MMP (w/o cRGD) > cRGD-MMP (w/o DTX) > DTX-cRGD-Ms (w/o DM1) > free DTX. Consequently, DTX-cRGD-MMP significantly improved the survival rates of B16F10 melanoma-bearing mice. Importantly, DTX-cRGD-MMP caused little adverse effects as revealed by mice body weights and histological analyses. The combination of two mitotic inhibitors, DTX and DM1, appears to be an interesting approach for effective cancer therapy.

Engineered Metal-Phenolic Capsules Show Tunable Targeted Delivery to Cancer Cells.

We engineered metal-phenolic capsules with both high targeting and low nonspecific cell binding properties. The capsules were prepared by coating phenolic-functionalized hyaluronic acid (HA) and poly(ethylene glycol) (PEG) on calcium carbonate templates, followed by cross-linking the phenolic groups with metal ions and removing the templates. The incorporation of HA significantly enhanced binding and association with a CD44 overexpressing (CD44+) cancer cell line, while the incorporation of PEG reduced nonspecific interactions with a CD44 minimal-expressing (CD44-) cell line. Moreover, high specific targeting to CD44+ cells can be balanced with low nonspecific binding to CD44- cells simply by using an optimized feed-ratio of HA and PEG to vary the content of HA and PEG incorporated into the capsules. Loading an anticancer drug (i.e., doxorubicin) into the obtained capsules resulted in significantly higher cytotoxicity to CD44+ cells but lower cytotoxicity to CD44- cells.

pH-Responsive Capsules Engineered from Metal-Phenolic Networks for Anticancer Drug Delivery.

A new class of pH-responsive capsules based on metal-phenolic networks (MPNs) for anticancer drug loading, delivery and release is reported. The fabrication of drug-loaded MPN capsules, which is based on the formation of coordination complexes between natural polyphenols and metal ions over a drug-coated template, represents a rapid strategy to engineer robust and versatile drug delivery carriers.

Enzymatically and reductively degradable α-amino acid-based poly(ester amide)s: synthesis, cell compatibility, and intracellular anticancer drug delivery.

A novel and versatile family of enzymatically and reductively degradable α-amino acid-based poly(ester amide)s (SS-PEAs) were developed from solution polycondensation of disulfide-containing di-p-toluenesulfonic acid salts of bis-l-phenylalanine diesters (SS-Phe-2TsOH) with di-p-nitrophenyl adipate (NA) in N,N-dimethylformamide (DMF). SS-PEAs with Mn ranging from 16.6 to 23.6 kg/mol were obtained, depending on NA/SS-Phe-2TsOH molar ratios. The chemical structures of SS-PEAs were confirmed by (1)H NMR and FTIR spectra. Thermal analyses showed that the obtained SS-PEAs were amorphous with a glass transition temperature (Tg) in the range of 35.2-39.5 °C. The in vitro degradation studies of SS-PEA films revealed that SS-PEAs underwent surface erosion in the presence of 0.1 mg/mL α-chymotrypsin and bulk degradation under a reductive environment containing 10 mM dithiothreitol (DTT). The preliminary cell culture studies displayed that SS-PEA films could well support adhesion and proliferation of L929 fibroblast cells, indicating that SS-PEAs have excellent cell compatibility. The nanoparticles prepared from SS-PEA with PVA as a surfactant had an average size of 167 nm in phosphate buffer (PB, 10 mM, pH 7.4). SS-PEA nanoparticles while stable under physiological environment undergo rapid disintegration under an enzymatic or reductive condition. The in vitro drug release studies showed that DOX release was accelerated in the presence of 0.1 mg/mL α-chymotrypsin or 10 mM DTT. Confocal microscopy observation displayed that SS-PEA nanoparticles effectively transported DOX into both drug-sensitive and -resistant MCF-7 cells. MTT assays revealed that DOX-loaded SS-PEA nanoparticles had a high antitumor activity approaching that of free DOX in drug-sensitive MCF-7 cells, while more than 10 times higher than free DOX in drug-resistant MCF-7/ADR cells. These enzymatically and reductively degradable α-amino acid-based poly(ester amide)s have provided an appealing platform for biomedical technology in particular controlled drug delivery applications.