science

Microbial drug delivery

Microbial drug delivery is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Microbial drug delivery rather than just read about it. In short: Microbial drug delivery is an emerging form of drug administration characterized by the use of commensal microbes that have been genetically modified to produce medications for chronic diseases in humans. Only proteinaceous drugs can be produced by microbes, as DNA encodes for protein.

Key takeaways

Microbial drug delivery belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Microbial drug delivery to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Microbial drug delivery from memory before moving on to harder problems.

Reference excerpt

Microbial drug delivery is an emerging form of drug administration characterized by the use of commensal microbes that have been genetically modified to produce medications for chronic diseases in humans. Only proteinaceous drugs can be produced by microbes, as DNA encodes for protein. Research into microbial drug delivery refers to this route of administration as topical, since the microbes release the drug directly to the surface of affected tissues, namely the gastrointestinal (GI) epithelium. Microbial drug delivery is not currently used as a standard route of drug administration due to its experimental nature. During clinical trials, it has been used to treat forms of inflammatory bowel disease (IBD). The most prominently studied vehicles of microbial drug administration are the bacterial species, Lactococcus lactis and Bacteroides ovatus.

Medical usage The usage of recombinant microbes (i.e. microorganisms designed to contain DNA from two or more different species) has applications in treating chronic diseases. In 2006, Braat et al. implemented microbial drug delivery with L. lactis in clinical trials, successfully treating Crohn's disease (CD), a form of IBD that causes inflammation and ulceration in the intestines. In this study, a recombinant strain of L. lactis containing complementary DNA (cDNA) for the human interleukin-10 (IL-10) gene was used to treat CD with IL-10, an anti-inflammatory cytokine. Patients consumed capsules containing the microbe to populate the intestines and received therapeutic doses of IL-10 directly from the recombinant bacteria. As this route of administration is experimental, it is currently not available as a standard treatment option. In a 2013 animal study with B. ovatus as the vehicle for microbial drug delivery, researcher Zaed Hamady suggested that recombinant strains of B. ovatus containing transforming growth factor-beta (TGF-β) and keratinocyte growth factor-2 (KGF-2) are ready for clinical trials.

Mechanism of drug administration

L. lactis mechanism The L. lactis mechanism of microbial drug delivery described in the 2006 study of Braat et al. uses a form of recombinant L. lactis (LL-Thy12) which has replaced the gene, Thy12, with the gene for human IL-10. Removal of Thy12, which encodes for the production of thymidine, causes L. lactis to become dependent on dietary thymidine to maintain live colonies in the gut. The addition of the IL-10 gene allows for the production of human IL-10 to decreases gut inflammation. Secretion of IL-10 from L. lactis in the gut is considered to be a topical administration of the drug to the epithelium, permitting healing in local tissues damaged by inflammation. The administration of IL-10 topically avoids systemic effects, such as immunosuppression in non-target tissues. When using LL-Thy12, IL-10 secretion is dependent on the quantity of live LL-Thy12 in the GI tract. As the presence of dietary thymidine increases the quantity of LL-Thy12, the drug production increases proportionately. Reductions in dietary thymidine kill LL-Thy12, decreasing the production of IL-10. There is a delay of approximately 72-hours between a change in thymidine dosage and the production of IL-10. Due to LL-Thy12’s dependence on thymidine, they will die upon exiting the body through defecation.

B. ovatus mechanism B. ovatus has been used in animal studies as a mode of microbial drug delivery due to its xylanase operon. Operons exist in bacteria to control gene expression and are composed of a DNA sequence containing an operator followed by the genes of interest. The operator in the xylanase operon prevents transcription of genes when bound to a repressor protein. The B. ovatus xylanase operon only functions in the presence of the starch, xylan, which removes the repressor and enables production of whichever proteins correlate with the genes located after the operator. For microbial drug delivery, the genes after the operator include those inserted as part of the genetic modification. Xylan is non-digestible to human gastric acid or digestive enzymes, so a predictable quantity of dietary xylan will reach the recombinant B. ovatus in the gut, hypothetically allowing for a precise quantity of drug to be produced by the recombinant B. ovatus. In mice, recombinant B. ovatus strains containing genes for growth factors TGF-β and KGF-2 within the xylanase operon have successfully treated ulcerative colitis (UC). The secreted drugs from B. ovatus are applied topically to the epithelial lining, affecting local tissues rather than acting systemically. Systemic administration of these growth factors could otherwise cause tumors and increased vascularization of tissues. When administered microbially, TGF-β and KGF-2 facilitate tissue repair only in the colon where they are released.

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Illustrations

Worked examples

Example 1 — a first encounter with Microbial drug delivery

Start with the simplest possible case. Write down what Microbial drug delivery claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Microbial drug delivery before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Microbial drug delivery ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Microbial drug delivery

In research: Microbial drug delivery appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Microbial drug delivery in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Microbial drug delivery is common in secondary-school and first-year university syllabi. It links to neighbouring topics Drug delivery devices, so understanding it makes those chapters shorter.
In everyday life: Look for Microbial drug delivery outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Microbial drug delivery in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Microbial drug delivery means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Microbial drug delivery out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Microbial drug delivery in simple terms?

Why does Microbial drug delivery matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Microbial drug delivery?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Microbial drug delivery.