Bacteriobot Drug-Liposome Carriers: An Optimization of Cancer-Drug Delivery to the Colon by Manipulating the Gut Microbiome

Cancer is a horrendous disease. The toxicity and the lack of effective chemotherapeutics that can reach and penetrate tumors plague the effectiveness of cancer treatment. Cancer is treatable when it is quickly diagnosed. Colon cancer occurs with the gradual accumulation of oncogenes that transform into tumors and metastatic disease. However, most drugs for cancer therapy in clinical trials for 2010 were found to be ineffective and failed. Oral administered drugs face degradation by gastric acids of the stomach, the bile salts of the liver, and by the acids of the small intestines. The drugs accumulate within the small intestines as a result and never reach the large intestines, the colon. Bacteria in the large intestines interact with drugs taken by oral administration. Bacteria in the gut breakdown and metabolize oral drugs, help to dispense, and distribute the drugs into lymphatic and blood circulation even into the gut-brain axis.


INTRODUCTION
The genes that cause cancer consist of multiple mutations. DOI: https://doi.org/10.35702/nano.10001 biomarkers for diagnosing and targeting cancerous cells with therapy have increased our understanding of molecular processes, diagnosis, and potential treatments. However, antibodies are profusely broad and cannot invade deep into tumors [2].
Cancer develops from the gradual collection of gene mutations overtime. Environmental factors for cancer development can be prevented with diet and other adaptations of beneficial behaviors. Hereditary causes for cancer can help with identifying at-risk and predisposed genotypes and disorders. However, R mutations or random mistakes made during DNA replication give us an understanding of the cancers that exist in some tissues and not others [3]. A vast majority of mortalities are attributed to cancer.
Treatment clinics do not provide total remission for patients because there is a lack of understanding of the molecular processes of the disease [4]. Tumor cells that spread to other tissues in the body are termed metastatic. These metastatic tumor cells consist of the original and the mutated cell duplicates. Cells within tumors and the tumor cells that are transported to other tissues are a significant contributor to cancer cell metastasis and renewal. Due to technology advancements as genomics and molecular procedures, drug discovery that is based on one target has immensely increased. Over the past 20 years, the drug discovery industry has experienced much growth; however, the effectiveness of the drugs discovered are characterized by reduced efficacy [5].
The most carcinogenic mutations reside within the RAS genes.
Pancreatic cancer is so deadly due to the KRAS gene mutation that results in the tumor becoming dangerously metastatic.
In 90 to 95 percent of patient cases, the KRAS gene has a significant role in the development of pancreatic cancer [6].
Pancreatic cancer has a terminal prognosis and outcome with a survival rate of five years or less. A mutation in the KRAS gene induces the initial development of pancreatic cancer. The three primary RAS genes in humans are KRAS, NRAS, and HRAS. The splicing of the KRAS gene produces two variants or types that are termed KRAS4A and KRAS4B. Most mutations for KRAS exist in the codons called G12, G13, and Q21 [6]. A KRAS mutation in the alleles for KRAS 4A and KRAS4B produces a mutation in the G12 codon [6]. A mutation in the G12 codon alters the glycine to aspartic acid that then permanently confirms the KRAS protein into a persistent active and oncogenic conformation.
The KRAS oncogene activates and induces downstream cascades of the RAF-mitogen activated protein kinase termed MAPK and the phosphoinositide-3-kinase or the PI3K pathway that augment the proliferation, survival, and the mobility of cancer cells [6].
Phosphorylation of targeted activities by proteins in signaling pathways and networks contribute to the development and pathogenesis of many cancers. Kinases that add phosphates produce most tumor cases from patients. Kinase signaling pathways contribute to increased cell growth, mobility into metastasis, survival, and cancer cell metabolism, and innate immune anticancer responses [7]. Disrupting the phosphorylation of proteins has become the focus and aim of cancer research and pharmacology. For example, a drug termed imatinib inhibits the protein BCR-ABL1 that results in chronic myelogenous leukemia and acute lymphoblastic leukemia [7]. Kinase inhibitors can suppress the oncogenic activities that contribute to a malignant cancerous condition.
The symbiotic relationship between commensal bacteria in the GI tract and the human condition currently lacks much understanding. The microflora in the gut produces and releases low weight organic molecules that regulate signaling networks and pathways. These organic molecules alter epigenetics, changes chromatin structure, upregulates apoptosis, monitors the differentiation of stem cells, and eliminates inflammation [8]. Because the small organic molecules released by bacterial microflora, cancer may be prevented and treated with alternative therapies.
Fewer gut bacteria results in humans lead to the increased amounts of fecal excrement containing estrogens with more double bonded phenyl groups and a lack of estrogens in the urine. Gut bacteria that can modulate the output of estrogen and other metabolites may provide therapeutic targets to combat cancer [8]. Therefore, the metabolic processes of gut bacteria can affect the delivery and absorption of drugs that change the pharmacologic expression of those drugs. The extent to which pharmaceutical drugs can reach further pass the proximal regions of the GI tract can affect can influence the metabolism of commensal gut bacteria and the different populations of gut bacterial groups. Many drugs lack optimal and productive interactions with gut bacteria due to the degradation of drugs in the stomach and the upper GI tract.
The composition of the gut bacteria can activate some drugs, inactivate others, or alter the pharmacologic components into toxic substances. The pharmacological activity of drugs relies on the stability and the widespread uptake of pharmaceutical drugs [9]. For example, commensal bacteria produce DOI: https://doi.org/10.35702/nano.10001 azoreductases that metabolize the edible and oral drug called sulfasalazine into a metabolite that relieves the inflammation of ulcerative colitis [9].
Nanoparticles are ideal carriers for drug delivery; however, capable nanocarriers require a design with optimal timedrelease and be able to load specific drug concentrations for advancing its circulation. For example, the uptake of drugs by tumors are characterized by diameters that are less than 100 nm [10]. However, the cancerous fibroblasts within tumors can block the advancement and penetration of a nanocarrier within cancerous tumors that proliferates angiogenesis and metastatic activities. The cells within these malignant The ingesting of drugs is the most challenging strategy of delivery. Ingested drugs can pass through the epithelial lining for blood circulation. If a drug has a specific solubility, is stable, is permeable across a lipid bilayer, and can be catabolized by gut microbiota, then the drug can effectively be delivered to its target site [9]. However, the metabolic interaction between a drug and the gut microbiota lacks specific and detailed study. The metabolism of drugs by gut bacteria alters drugs into phytochemicals that do not usually reside in the living organism. Gut bacteria release enzymes that metabolize drugs before the drug uptake from the GI tract into blood circulation.
Unlike the liver, the gut microbiota produces hydrophobic metabolites through the redox-oxidative process of reduction and hydrolysis [9].
Hydrophilic types of oral drugs are not degraded by the gastric acids of the stomach and the pancreas, so these types of hydrophilic drugs reach the small intestines into the large intestines in which many gut commensal and microbiota inhabit. The bacterial gut microbiota alters the hydrophilic drugs into hydrophobic compounds [9]. The absorption of the hydrophobic compounds leads to the expression and the exertion of its pharmacological effects. Another factor includes the half-life of a drug that can lead to its therapeutic effectiveness. The half-life of many cancer drugs is minute due to their being vastly hydrophobic, highly degradable, and low in molecular weight. Therefore, the cancer drug is excreted from the body quickly, lessening the effectiveness of therapy in the tumor. The use of nanoparticles as drug carriers designed into spheres of micelles, attached to PEGs that are hydrophilic, optimizes the timed-release of the cancer drugs into the blood circulation [10]. Because most cancer drugs are designed into spheres of nanocarriers, there is a gap in the study of the effects of nanoparticle shape. Nanoparticle shape affects the absorption and its uptake by cells.
Nanocarriers shaped like worms have the worst active uptake by macrophages due to its increased degradability by hydrolysis. Researchers studied the uptake of sphere-like versus cylinder-like nanocarriers and found that the cylindrical nanoparticles had less frequent uptake by CHO cells compared to the spherical nanocarriers [10].
A more effective drug-delivery system was found using nanoparticles and nanotechnology. Nanoparticles are submicron particles that are 100 to 1000 nm in size with different physical and chemical components [11]. The use of nanoparticles is highly favorable in cancer drug research since nanoparticles can lead to an extended timed release of anticancer drug components, lessening toxic side effects. The use of liposomes in drug design is beneficial since it reduces the adverse side effects of chemotherapy as it optimizes the effectiveness of its anticancer cargo that is carried. Liposomes more specifically deliver its anticancer cargo to its target sites within cells and tumors through its active and passive Medicines Agency and the US Food and Drug Administration has approved many hydrophilic chemotherapeutic agents carried by liposomes duet to many successful prognoses of clinical studies [11].
The design of liposomes as nanocarriers of anticancer therapeutics has produced many positive results and outcomes where currently, liposomes are formulated to express pH-sensitivity, temperature-sensitivity, and sensitivity to magnetic fields [11]. There are also new novel liposome designs with an emphasis upon lipid nanoparticles, lipid vehicles, and lipid polymer nanoparticles that can remedy the issues for effective liposomal delivery [11].
According to the NCI updated report or National Cancer Institute Budget Proposal for 2010, the list of significant cancer funded studies included the following: for its anti-inflammatory effects immensely decrease after the administration of chemotherapy [13]. The focus of current therapeutic designs reduces toxicity but does not manipulate the gut microbiota to restore the effectiveness of chemotherapeutics.
The probiotic yogurt called Yakult was given to children.
Doctors administered chemotherapy to those children and gave them Yakult consisting of B. breve probiotics [13]. The The fecal matter from these patients was transferred to mice, and the mice showed antitumor effects when given the PD-1 inhibitor.
The manipulation of the microbiota that resides in the gut can improve the effectiveness of chemotherapeutic drugs.
The combination of antibiotics with probiotics lowered the rate of irinotecan, a cancer drug, forming mucositis in mice.
A lack of diversity and variations of bacterial populations reduced the survival rate by 31% [14]. Researchers studied 857 cancer patients with allo-HSCT, and they found that the use of antibiotics propagated pathogenic bacteria as Akkermansia muciniphila, leading to the failure of graft-versus-host disease. The GVHD yielded a mortality rate of 5 years. The Akkermansia muciniphila proliferated after antibiotic use, and epithelial lining of the colon deteriorated as the GVHD spread.
Issues include 1) inability to target tumors, 2) unable to intrude tissues, and 3) a need for less toxicity to cancer cells [15]. These issues of drug delivery will negatively affect cancer treatments, resulting in higher rates of mortality. However, manipulating the microbiome through the bacteria termed

Tumor penetration and proliferation
Bacteria as Salmonellae can more deeply penetrate tumors with chemotherapeutics due to the high rate and velocity of their motility properties. Because of their ability to become mobile, they can navigate around cumbersome blood vessels; these bacteria can populate the total span of a tumor.
Salmonellae were engineered to carry microbeads throughout a tumor. The bacterial strain of S. typhimurium fills tumors at a higher rate than healthy organs at approximately 1,000-fold higher with 1010 CFU/g of tissue [15]. Bacteria that grow and populate in tumors starve the tumors of nutrients, initiate immune responses, and cause apoptosis.

Immune stimulation
Tumors innately inhibit the development of immune responses and escape most immune responses. S. typhimurium induce immune responses that produce suppression of tumor growth.
S. typhimurium has flagellin, LPS, and CpG sites that bind to toll-like receptors or TLRs that identify antigens. Activating the TLRs generate innate and adaptive immunity [15].

Programmability
Clinical research in phase I for the study of VNP200009 proves the ability of chemotherapeutics to invade and be delivered into tumors is a severe issue for advancing cancer research [15]. Therefore, the delivery of therapeutics through  [15]. Also, Park et al. produced research for their findings in the "New paradigm for tumor theranostic methodology using bacteria-based microrobot" that presents a method of In-vitro and in-vivo tests that confirmed their constructed bacteriobots displayed chemotactic motility and tumor targeting capabilities [17]. They concluded that "The new bacteriobots act as microactuators and microsensors to deliver microstructures to tumors" [17].

Possible Outcomes
The importance of the research outcomes We will be able to test various molecular weights of the liposome carrier. The weight of 40kDa is above the renal threshold and allows a feasible lymphatic clearance of nanoparticles [12].

Theoretical outcome
In theory, the use of liposomes to carry small cancer inhibitors will enhance the delivery.