Bacteriological Profile of Surgical Site Infection Following Gastrointestinal Surgery and Their Antibiogram.

BACKGROUND: Surgical site infection is one of the common complication following abdominal surgery. It causes great morbidity and mortality, further increasing prevalence of multidrug resistant bacteria have made its management very challenging. The current study aims to identify causative agent responsible for surgical site infection and their antibiotic resistance patterns. METHODS: This study was conducted among patients developing surgical site infection following gastrointestinal surgery in Tribhuvan university teaching hospital over a period of one year. The samples were collected and processed according to standard methods. The bacterial pathogens with their antimicrobial susceptibility were determined and resistant pattern like methicillin resistant Staphylococcus aureus and extended spectrum beta lactamase were further detected. RESULTS: A total of 832 patients had under gone gastrointestinal surgery during the study period. Among them, 162 cases (19.5%) developed surgical site infection and 125 cases showed growth in culture. A total of 160 aerobic bacteria were isolated; Escherichia coli (29.9%) was the commonest organism with 40.8% being extended spectrum beta lactamase producer and 47.4% of Staphylococcus aureus were methicillin resistant. About 75.9% (85/112) of gram negative bacteria and 60.4% (29/48) gram positive bacteria were multi drug resistant. CONCLUSIONS: The burden of multi drug resistant bacteria causing surgical site infection is high which needs to be addressed timely. Good surveillance of bacterial antibiogram and rational antimicrobial use is necessary to reduce emergence and spread of resistant bacteria.

The Lysyl Oxidase G473A Polymorphism Exacerbates Oral Cancer Development in Humans and Mice.

Oral cancer is primarily squamous-cell carcinoma with a 5-year survival rate of approximately 50%. Lysyl oxidase (LOX) participates in collagen and elastin maturation. The propeptide of LOX is released as an 18 kDa protein (LOX-PP) in the extracellular environment by procollagen C-proteinases and has tumor-inhibitory properties. A polymorphism in the propeptide region of LOX (rs1800449, G473A) results in a single amino acid substitution of Gln for Arg. Here we investigated the frequency of rs1800449 in OSCC employing TCGA database resources and determined the kinetics and severity of precancerous oral lesion development in wildtype and corresponding knockin mice after exposure to 4-nitroquinoline oxide (4 NQO) in drinking water. Data show that the OSCC is more common in humans carrying the variant compared to the wildtype. Knockin mice are more susceptible to lesion development. The immunohistochemistry of LOX in mouse tissues and in vitro studies point to a negative feedback pathway of wildtype LOX-PP on LOX expression that is deficient in knockin mice. Data further demonstrate modulations of T cell phenotype in knockin mice toward a more tumor-permissive condition. Data provide initial evidence for rs1800449 as an oral cancer susceptibility biomarker and point to opportunities to better understand the functional mechanism of LOX-PP cancer inhibitory activity.

Multifunctional Self-Assembled Peptide Hydrogels for Biomedical Applications.

Self-assembly is a growth mechanism in nature to apply local interactions forming a minimum energy structure. Currently, self-assembled materials are considered for biomedical applications due to their pleasant features, including scalability, versatility, simplicity, and inexpensiveness. Self-assembled peptides can be applied to design and fabricate different structures, such as micelles, hydrogels, and vesicles, by diverse physical interactions between specific building blocks. Among them, bioactivity, biocompatibility, and biodegradability of peptide hydrogels have introduced them as versatile platforms in biomedical applications, such as drug delivery, tissue engineering, biosensing, and treating different diseases. Moreover, peptides are capable of mimicking the microenvironment of natural tissues and responding to internal and external stimuli for triggered drug release. In the current review, the unique characteristics of peptide hydrogels and recent advances in their design, fabrication, as well as chemical, physical, and biological properties are presented. Additionally, recent developments of these biomaterials are discussed with a particular focus on their biomedical applications in targeted drug delivery and gene delivery, stem cell therapy, cancer therapy and immune regulation, bioimaging, and regenerative medicine.

Impact of PEGylation on an antibody-loaded nanoparticle-based drug delivery system for the treatment of inflammatory bowel disease.

Nanoparticle-based oral drug delivery systems have the potential to target inflamed regions in the gastrointestinal tract by specifically accumulating at disrupted colonic epithelium. But, delivery of intact protein drugs at the targeted site is a major challenge due to the harsh gastrointestinal environment and the protective mucus layer. Biocompatible nanoparticles engineered to target the inflamed colonic tissue and efficiently penetrate the mucosal layer can provide a promising approach for orally delivering monoclonal antibodies to treat inflammatory bowel disease. The study aims to develop mucus-penetrating nanoparticles composed of poly(lactic-co-glycolic acid, PLGA) polymers with two different polyethylene glycol (PEG) chain lengths (2 kDa and 5kDa) to encapsulate monoclonal antibody against tumor necrosis factor-α (TNF-α). The impact of different PEG chain lengths on the efficacy of the nanosystems was evaluated in vitro, ex vivo, and in vivo. Both PLGA-PEG2k and PLGA-PEG5k nanoparticles successfully encapsulated the antibody and significantly reduced TNF-α secretion from activated macrophages and intestinal epithelial cells. However, only antibody-loaded PLGA-PEG2k nanoparticles were able to alleviate the experimental acute colitis in mice demonstrated by improved colon weight/length ratio, histological score, and reduced tissue-associated myeloperoxidase activity and expression of proinflammatory cytokine TNF-α levels compared with the control group. The results suggest that despite having no significant differences in the in vitro cell-based assays, PEG chain length has a significant impact on the in vivo performance of the mucus penetrating nanoparticles. Overall, PLGA-PEG2k nanoparticles were presented as a promising oral delivery system for targeted antibody delivery to treat inflammatory bowel disease. STATEMENT OF SIGNIFICANCE: There is an unmet therapeutic need for oral drug delivery systems for safe and effective antibody therapy of inflammatory bowel disease. Therefore, we have developed PEGylated PLGA-based nanoparticulate drug delivery systems for oral targeted delivery of anti-TNF-α antibody as a potential alternative treatment strategy. The PEG chain length did not affect encapsulation efficiency or interaction with mucin in vitro but resulted in differences in in vitro release profile and in vivo efficacy study. We demonstrated the superiority of anti-TNF-α mAb-PLGA-PEG2k over mAb-PLGA-PEG5k nanoparticles to effectively exhibit anti-inflammatory responses in an acute murine colitis model. These nanoparticle-based formulations may be adjusted to encapsulate other drugs that could be applied to a number of disorders at different mucosal surfaces.

A nanoemulsion/micelles mixed nanosystem for the oral administration of hydrophobically modified insulin.

The potential of nanoemulsions for the oral administration of peptides is still in its early stage. The aim of the present work was to rationally design, develop, and fully characterize a new nanoemulsion (NE) intended for the oral administration of hydrophobically modified insulin (HM-insulin). Specific components of the NE were selected based on their enhancing permeation properties as well as their ability to improve insulin association efficiency (Miglyol 812, sodium taurocholate), stability in the intestinal fluids, and mucodiffusion (PEGylated phospholipids and poloxamer 407). The results showed that the NE co-existed with a population of micelles, forming a mixed system that exhibited a 100% of HM-insulin association efficiency. The nanosystem showed good stability and miscibility in different bio-relevant media and displayed an acceptable mucodiffusive behavior in porcine mucus. In addition, it exhibited a high interaction with cell mono-cultures (Caco -2 and C2BBe1 human colon carcinoma Caco-2 clone cells) and co-cultures (C2BBe1 human colon carcinoma Caco-2 clone/HT29-MTX cells). The internalization in Caco-2 monolayers was also confirmed by confocal microscopy. Finally, the promising in vitro behavior of the nanosystem in terms of overcoming the biological barriers of the intestinal tract was translated into a moderate, although significant, hypoglycemic response (≈ 20-30%), following intestinal administration to both healthy and diabetic rat models. Overall, this information underlines the crucial steps to address when designing peptide-based nanoformulations to successfully overcome the intestinal barriers associated to the oral modality of administration.

Overcoming the intestinal barrier: A look into targeting approaches for improved oral drug delivery systems.

Oral drug administration is one of the most preferred and simplest routes among both patients and formulation scientists. Nevertheless, orally delivery of some of the most widely used therapeutic agents (e.g., anticancer drugs, peptides, proteins and vaccines) is still a major challenge due to the limited oral bioavailability associated with them. The poor oral bioavailability of such drugs is attributed to one or many factors, such as poor aqueous solubility, poor permeability, and enzymatic degradation. Various technological strategies (such as permeation enhancers, prodrugs and nanocarriers) have been developed to enhance the bioavailability of these drugs after oral administration. Among the different approaches, advanced and innovative drug delivery systems, especially targeting-based strategies, have garnered tremendous attention. Furthermore, the presence of numerous types of cells and solute carrier transporters throughout the gastrointestinal tract represents numerous potential targeting sites for successful oral delivery that have not yet been exploited for their full potential. This review describes different targeting strategies towards different targeting sites in the gastrointestinal tract. Additionally, exciting improvements in oral drug delivery systems with different targeting strategies (e.g., M cells for oral vaccination and L cells for type 2 diabetes mellitus) are also discussed.

Mechanism for oral tumor cell lysyl oxidase like-2 in cancer development: synergy with PDGF-AB.

Extracellular lysyl oxidases (LOX and LOXL1-LOXL4) are critical for collagen biosynthesis. LOXL2 is a marker of poor survival in oral squamous cell cancer. We investigated mechanisms by which tumor cell secreted LOXL2 targets proximal mesenchymal cells to enhance tumor growth and metastasis. This study identified the first molecular mechanism for LOXL2 in the promotion of cancer via its enzymatic modification of a non-collagenous substrate in the context of paracrine signaling between tumor cells and resident fibroblasts. The role and mechanism of active LOXL2 in promoting oral cancer was evaluated and employed a novel LOXL2 small molecule inhibitor, PSX-S1C, administered to immunodeficient, and syngeneic immunocompetent orthotopic oral cancer mouse models. Tumor growth, histopathology, and metastases were monitored. In vitro mechanistic studies with conditioned tumor cell medium treatment of normal human oral fibroblasts were carried out in the presence and absence of the LOXL2 inhibitor to identify signaling mechanisms promoted by LOXL2 activity. Inhibition of LOXL2 attenuated cancer growth and lymph node metastases in the orthotopic tongue mouse models. Immunohistochemistry data indicated that LOXL2 expression in and around tumors was decreased in mice treated with the inhibitor. Inhibition of LOXL2 activity by administration of PXS-S1C to mice reduced tumor cell proliferation, accompanied by changes in morphology and in the expression of epithelial to mesenchymal transition markers. In vitro studies identified PDGFRß as a direct substrate for LOXL2, and indicated that LOXL2 and PDGF-AB together secreted by tumor cells optimally activated PDGFRß in fibroblasts to promote proliferation and the tendency toward fibrosis via ERK activation, but not AKT. Optimal fibroblast proliferation in vitro required LOXL2 activity, while tumor cell proliferation did not. Thus, tumor cell-derived LOXL2 in the microenvironment directly targets neighboring resident cells to promote a permissive local niche, in addition to its known role in collagen maturation.

Social Stimulus Causes Aberrant Activation of the Medial Prefrontal Cortex in a Mouse Model With Autism-Like Behaviors.

Autism spectrum disorder (ASD) is a highly prevalent and genetically heterogeneous brain disorder. Developing effective therapeutic interventions requires knowledge of the brain regions that malfunction and how they malfunction during ASD-relevant behaviors. Our study provides insights into brain regions activated by a novel social stimulus and how the activation pattern differs between mice that display autism-like disabilities and control littermates. Adenomatous polyposis coli (APC) conditional knockout (cKO) mice display reduced social interest, increased repetitive behaviors and dysfunction of the ß-catenin pathway, a convergent target of numerous ASD-linked human genes. Here, we exposed the mice to a novel social vs. non-social stimulus and measured neuronal activation by immunostaining for the protein c-Fos. We analyzed three brain regions known to play a role in social behavior. Compared with control littermates, APC cKOs display excessive activation, as evidenced by an increased number of excitatory pyramidal neurons stained for c-Fos in the medial prefrontal cortex (mPFC), selectively in the infralimbic sub-region. In contrast, two other social brain regions, the medial amygdala and piriform cortex show normal levels of neuron activation. Additionally, APC cKOs exhibit increased frequency of miniature excitatory postsynaptic currents (mEPSCs) in layer 5 pyramidal neurons of the infralimbic sub-region. Further, immunostaining is reduced for the inhibitory interneuron markers parvalbumin (PV) and somatostatin (SST) in the APC cKO mPFC. Our findings suggest aberrant excitatory-inhibitory balance and activation patterns. As ß-catenin is a core pathway in ASD, we identify the infralimbic sub-region of the mPFC as a critical brain region for autism-relevant social behavior.

Intracellular responsive dual delivery by endosomolytic polyplexes carrying DNA anchored porous silicon nanoparticles.

Bioresponsive cytosolic nanobased multidelivery has been emerging as an enormously challenging novel concept due to the intrinsic protective barriers of the cells and hardly controllable performances of nanomaterials. Here, we present a new paradigm to advance nano-in-nano integration technology amenable to create multifunctional nanovehicles showing considerable promise to overcome restrictions of intracellular delivery, solve impediments of endosomal localization and aid effectual tracking of nanoparticles. A redox responsive intercalator chemistry comprised of cystine and 9-aminoacridine is designed as a cross-linker to cap carboxylated porous silicon nanoparticles with DNA. These intelligent nanocarriers are then encapsulated within novel one-pot electrostatically complexed nano-networks made of a zwitterionic amino acid (cysteine), an anionic bioadhesive polymer (poly(methyl vinyl ether-alt-maleic acid)) and a cationic endosomolytic polymer (polyethyleneimine). This combined nanocomposite is successfully tested for the co-delivery of hydrophobic (sorafenib) or hydrophilic (calcein) molecules loaded within the porous core, and an imaging agent covalently integrated into the polyplex shell by click chemistry. High loading capacity, low cyto- and hemo-toxicity, glutathione responsive on-command drug release, and superior cytosolic delivery are shown as achievable key features of the proposed formulation. Overall, formulating drug molecules, DNA and imaging agents, without any interference, in a physico-chemically optimized carrier may open a path towards broad applicability of these cost-effective multivalent nanocomposites for treating different diseases.

Microfluidic Assembly of a Multifunctional Tailorable Composite System Designed for Site Specific Combined Oral Delivery of Peptide Drugs.

Multifunctional tailorable composite systems, specifically designed for oral dual-delivery of a peptide (glucagon-like peptide-1) and an enzymatic inhibitor (dipeptidyl peptidase 4 (DPP4)), were assembled through the microfluidics technique. Both drugs were coloaded into these systems for a synergistic therapeutic effect. The systems were composed of chitosan and cell-penetrating peptide modified poly(lactide-co-glycolide) and porous silicon nanoparticles as nanomatrices, further encapsulated in an enteric hydroxypropylmethylcellulose acetylsuccinate polymer. The developed multifunctional systems were pH-sensitive, inherited by the enteric polymer, enabling the release of the nanoparticles only in the simulated intestinal conditions. Moreover, the encapsulation into this polymer prevented the degradation of the nanoparticles' modifications. These nanoparticles showed strong and higher interactions with the intestinal cells in comparison with the nonmodified ones. The presence of DPP4 inhibitor enhanced the peptide permeability across intestinal cell monolayers. Overall, this is a promising platform for simultaneously delivering two drugs from a single formulation. Through this approach peptides are expected to increase their bioavailability and efficiency in vivo both by their specific release at the intestinal level and also by the reduced enzymatic activity. The use of this platform, specifically in combination of the two antidiabetic drugs, has clinical potential for the therapy of type 2 diabetes mellitus.

Multistage pH-responsive mucoadhesive nanocarriers prepared by aerosol flow reactor technology: A controlled dual protein-drug delivery system.

Nanotechnology based drug delivery systems are anticipated to overcome the persistent challenges in oral protein and peptide administration, and lead to the development of long awaited non-invasive therapies. Herein, an advanced single-step aerosol flow reactor based technology was used to develop a multifunctional site specific dual protein-drug delivery nanosystem. For this purpose, mucoadhesive porous silicon (PSi) nanoparticles encapsulated into a pH-responsive polymeric nanomatrix was developed for advanced oral type 2 diabetes mellitus therapy with an antidiabetic peptide, glucagon like peptide-1 (GLP-1), and the enzyme inhibitor, dipeptidyl peptidase-4 (DPP4). Chitosan surface modification inherited the mucoadhesiveness to the nanosystem which led to enhanced cellular interactions and increased cellular compatibility. An advanced aerosol flow reactor technology was used to encapsulate the chitosan modified nanoparticles into an enteric polymeric nanomatrix. The pH-sensitive polymeric matrix simultaneously prevented the gastric degradation of the encapsulated peptide and also preserved the mucoadhesive functionality of the chitosan-modified PSi nanoparticles in the harsh stomach environment. The multidrug loaded nanosystem showed augmented intestinal permeability of GLP-1, evaluated in an in vitro cell-based intestinal epithelium model, attributed to the permeation enhancer effect of chitosan and inhibition of GLP-1 degradation by the DPP4 inhibitor. The applied technology resulted in the development of a dual-drug delivery nanosystem that synergizes the antidiabetic effect of the loaded peptide and the enzyme inhibitor, thereby indicating high clinical potential of the system and preparation technique.

Control of neural cell composition in poly(ethylene glycol) hydrogel culture with soluble factors.

Poly(ethylene glycol) (PEG) hydrogels are being developed as cell delivery vehicles that have great potential to improve neuronal replacement therapies. Current research priorities include (1) characterizing neural cell growth within PEG hydrogels relative to standard culture systems and (2) generating neuronal-enriched populations within the PEG hydrogel environment. This study compares the percentage of neural precursor cells (NPCs), neurons, and glia present when dissociated neural cells are seeded within PEG hydrogels relative to standard monolayer culture. Results demonstrate that PEG hydrogels enriched the initial cell population for NPCs, which subsequently gave rise to neurons, then to glia. Relative to monolayer culture, PEG hydrogels maintained an increased percentage of NPCs and a decreased percentage of glia. This neurogenic advantage of PEG hydrogels is accentuated in the presence of basic fibroblast growth factor and epidermal growth factor, which more potently increase NPC and neuronal expression markers when applied to cells cultured within PEG hydrogels. Finally, this work demonstrates that glial differentiation can be selectively eliminated upon supplementation with a γ-secretase inhibitor. Together, this study furthers our understanding of how the PEG hydrogel environment influences neural cell composition and also describes select soluble factors that are useful in generating neuronal-enriched populations within the PEG hydrogel environment.