Description

Technical Parameters

Introduction

peptides

product-1400-1400

Products Description

### Systematic classification and characteristic analysis of recombinant human growth hormone (HGH 191aa)

Recombinant human growth hormone (HGH 191aa) is a protein composed of 191 amino acids. It is produced by genetic engineering technology and is widely used in medical, scientific research and anti-aging fields. This article will systematically analyze its classification, physical and chemical properties, advantages and disadvantages, and color characteristics from four dimensions: molecular structure modification, expression system, formulation form, and application field, and provide a comprehensive technical analysis.

### 1. Classification based on molecular structure modification

#### 1. **Unmodified HGH (rhGH)**

- **Structure and characteristics**: Consistent with the structure of natural human growth hormone, no chemical modification, molecular weight of about 22 kDa, isoelectric point (pI) 5.3.

- **Advantages**: High biological activity (>3.0 IU/mg), close to 100% binding efficiency with natural hormone receptors.

- **Physical and chemical properties**:

- **Solubility**: Easily soluble in pH 7.4 buffer, the lyophilized powder is a colorless and transparent liquid after reconstitution.

- **Stability**: The lyophilized state can be stored for 2 years at 2-8°C; liquid preparations need to be refrigerated and are prone to aggregation due to temperature fluctuations or mechanical stress.

- **Color characteristics**: The lyophilized powder is white or off-white (with mannitol or glycine added as an excipient), and the solution is clear and colorless.

- **Representative products**: Genotropin (Pfizer), Norditropin (Novo Nordisk).

#### 2. **PEGylated HGH (PEG-rhGH)**

- **Structural modification**: Polyethylene glycol (PEG) molecules are connected by covalent bonds to extend the half-life (from 4-6 hours to 48 hours).

- **Advantages**: 1-2 injections per week, significantly improving patient compliance.

- **Physical and chemical properties**:

- **Molecular weight**: varies depending on the length of the PEG chain (usually increases by 10-40 kDa).

- **Solubility**: slightly lower than the unmodified type, requiring a specific buffer system (such as phosphate buffer).

- **Stability**: The PEG layer reduces enzymatic degradation and immunogenicity, and the liquid is more stable at room temperature.

- **Color characteristics**: The lyophilized powder is slightly yellow (PEG oxidation may cause slight discoloration), and the solution is light milky white.

- **Representative products**: Pegvisomant (rarely used for acromegaly, non-standard HGH replacement therapy).

#### 3. **Fatty acid modified HGH (such as Albutropin)**

- **Structural modification**: Covalent bonding through fatty acid chains (such as C14-C18) to form a sustained-release structure.

- **Advantages**: The half-life is extended to 7 days, suitable for long-term treatment in pediatrics.

- **Physical and chemical properties**:

- **Enhanced hydrophobicity**: Surfactants (such as polysorbate 80) are required to improve solubility.

- **Thermal stability**: freeze-dried state is resistant to high temperature (activity retention >95% after 3 months at 25°C).

- **Color characteristics**: freeze-dried powder is pure white, and the solution may be slightly turbid due to surfactants.

### 2. Classification based on expression system

#### 1. **Escherichia coli expression system**

- **Production process**: through inclusion body expression, renaturation step is required, and the cost is low.

- **Advantages**: high yield (>1 g/L), suitable for large-scale production.

- **Physical and chemical differences**:

- **No glycosylation**: compared with natural HGH, it may affect the in vivo clearance rate.

- **Purity control**: host protein residues need to be <0.1% (detected by HPLC).

- **Color characteristics**: high-purity products are white freeze-dried powder, low-purity products may be yellowish (host nucleic acid residues).

#### 2. **Mammalian cell expression system (such as CHO cells)**

- **Production process**: secretory expression, no renaturation required, retaining the natural folding conformation.

- **Advantages**: Glycosylation modification is close to the human body and has lower immunogenicity.

- **Physical and chemical differences**:

- **Glycosylation sites**: Although HGH is naturally non-glycosylated, the CHO system may introduce trace modifications.

- **Stability**: Liquid preparations are more resistant to repeated freezing and thawing.

- **Color characteristics**: The solution has higher clarity and the freeze-dried powder has a looser texture.

### 3. Classification based on the form of preparations

#### 1. **Lyophilized powder injection**

- **Formula composition**: HGH, mannitol, sodium phosphate buffer system.

- **Advantages**: Excellent long-term stability and easy transportation.

- **Physical and chemical parameters**:

- **Reconstitution time**: <1 minute (related to the crystallinity of the excipient).

- **pH value**: 6.8-7.8, close to the physiological environment.

- **Color change**: If stored improperly (high temperature/light), it may turn light pink due to oxidation.

#### 2. **Prefilled liquid dosage form**

- **Formula innovation**: Add non-ionic surfactants (such as Poloxamer 188) to inhibit aggregation.

- **Advantages**: Ready to use and convenient, reducing the risk of operational contamination.

- **Physical and chemical parameters**:

- **Viscosity**: 1.2-1.5 cP, close to water.

- **Storage conditions**: 18 months at 2-8℃, some brands support short-term storage at 25℃.

- **Color characteristics**: Transparent and colorless, if flocs appear, it indicates protein denaturation.

### 4. Classification based on application areas

#### 1. **Medical grade HGH**

- **Indications**: Growth hormone deficiency (GHD) in children, Turner syndrome, chronic renal insufficiency.

- **Quality control**: Meet USP/EP standards, endotoxin <5 EU/mg, host DNA <10 ng/dose

- **Packaging specifications**: multi-dose cartridges (such as Norditropin FlexPro®), supporting dose adjustment.

#### 2. **Research-grade HGH**

- **Features**: Purity > 95% (SDS-PAGE verification), containing trace preservatives (such as phenol).

- **Application scenarios**: cell proliferation experiments, receptor binding studies (such as using radiolabeled HGH).

#### 3. **Anti-aging/sports enhancement products**

- **Controversy**: non-regulatory use, commonly found in the gray market.

- **Risks**: insufficient purity (some products detected < 70% purity), may contain bacterial protein sensitization.

### 5. Comprehensive performance comparison and future trends

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**Future development direction**:

- **Oral delivery system**: Nanoliposome encapsulation technology to improve bioavailability.

- **Intelligent controlled release**: Microneedle patch that responds to pH or enzyme environment.

- **Gene therapy**: Continuous expression of endogenous HGH through AAV vectors.

### Conclusion

The diverse classification of HGH 191aa reflects the progress of biopharmaceutical technology. Medical-grade products are strictly controlled in terms of purity and safety, and long-acting modifications significantly improve the quality of life of patients. In the future, with the development of formulation innovation and gene editing technology, HGH therapy will evolve in a more efficient and convenient direction.